Wastewater Integrated Master Plan

WASTEWATER INTEGRATED MASTERPLAN DECEMBER, 2008

Internally Authored By:

Colorado Springs Utilities

Wastewater Planning and Design

Industrial Pretreatment

Wastewater Programs

WASTEWATER INTEGRATED MASTERPLAN TABLE OF CONTENTS

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TABLE OF CONTENTS

Tables................................................................................................................................................................ iii

Figures ............................................................................................................................................................... v

Executive Summary ......................................................................................................................................... vii

ES 1. Collection System Masterplan ............................................................................................vii

ES 2. Wastewater Treatment Facilities Masterplan....................................................................... ix

ES 3. Solids Handling & Disposal Masterplan.............................................................................. xi

1. Overview of Wastewater System ...........................................................................................................1-1

1.1. Collection System .............................................................................................................1-2

1.2. Treatment Facilities ..........................................................................................................1-7

1.3. Biosolids Facility (SHDF) ..............................................................................................1-11

1.4. Future Development........................................................................................................1-11

2. Collection System Masterplan ...............................................................................................................2-1

2.1. Wastewater Collection System Modeling.........................................................................2-2

2.1.1. Hydraulic Model Development.................................................................................2-3

2.1.2. Capacity Evaluation ..................................................................................................2-8

2.1.3. Level of Service ......................................................................................................2-12

2.1.4. Potential Capital Improvements..............................................................................2-13

2.2. Wastewater Programs .....................................................................................................2-16

2.2.1. Sanitary Sewer Evaluation and Rehabilitation Program (SSERP) .........................2-16

2.2.2. Local Collectors Evaluation and Rehabilitation Program (LCERP) ......................2-24

2.2.3. Sanitary Sewer Creek Crossings Program (SSCC).................................................2-29

2.2.4. Other Programs .......................................................................................................2-32

2.3. Fats, Oil and Grease Evaluation......................................................................................2-33

3. Wastewater Treatment Facilities Masterplan .........................................................................................3-1

3.1. Las Vegas Street Wastewater Treatment Facility.............................................................3-1

3.1.1. Description................................................................................................................3-1

3.1.2. Capacity Evaluation ..................................................................................................3-1

3.1.3. Facility Improvements ............................................................................................3-11

3.1.4. Regulatory Evaluation ............................................................................................3-15

3.1.5. Alternatives Development ......................................................................................3-18

3.1.6. Capital Improvements and O&M Program.............................................................3-19


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3.2. J.D. Phillips Wastewater Reclamation Facility .............................................................. 3-19

3.2.1. Description.............................................................................................................. 3-19

3.2.2. Facility Condition and Capacity Evaluation........................................................... 3-19

3.2.3. Future Capacity Requirements Analysis ................................................................ 3-19

3.2.4. Regulatory Evaluation ............................................................................................ 3-19

3.2.5. Capital Improvements and O&M Program............................................................. 3-19

4. Solids Handling & Disposal Facility Masterplan .................................................................................4-19

4.1. Description...................................................................................................................... 4-19

4.2. Facility Condition and Capacity Evaluation................................................................... 4-19

4.2.1. Blended Sludge Pump Station ................................................................................ 4-19

4.2.2. Sludge Main............................................................................................................ 4-19

4.2.3. Anaerobic Digesters................................................................................................ 4-19

4.2.4. Facultative Sludge Basins (FSBs) .......................................................................... 4-19

4.2.5. Dedicated Land Disposal Units (DLDs)................................................................. 4-19

4.2.6. Supernatant Handling System................................................................................. 4-19

4.3. Regulatory Evaluation .................................................................................................... 4-19

4.3.1. Air Quality Requirements....................................................................................... 4-19

4.3.2. Federal Regulations ................................................................................................ 4-19

4.3.3. Monitoring Requirements....................................................................................... 4-19

4.3.4. State and Local Regulations ................................................................................... 4-19

4.4. Alternatives Development .............................................................................................. 4-19

4.4.1. Digester Covers ...................................................................................................... 4-19

4.4.2. Impacts from New Impoundment Regulations....................................................... 4-19

4.4.3. Digester Gas – Energy Recovery............................................................................ 4-19

4.5. Capital Improvements Budget ........................................................................................ 4-19

5. Glossary................................................................................................................................................5-19

6. Index.....................................................................................................................................................6-19


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TABLES

Table ES-1 – 10 Year Capital Budget for Collection System Projects (in millions) ............................. ix

Table ES-2 – Budgeted Amounts for Capital Projects at LVSWWTF (in millions)............................... xi

Table ES-3 – Budgeted Amounts for Capital Projects at SHDF (in millions)....................................... xii

Table 2-1 – Lift Station Data .......................................................................................................................2-5

Table 2-2 – Wet Weather Storm Event Data ...........................................................................................2-7

Table 2-3 – Potential Capital Improvement Projects ............................................................................2-14

Table 2-4 - Basin Prioritization of Interceptors/Trunk Lines and Collectors ......................................2-20

Table 2-5 – Colorado Springs Utilities Response Coding System .....................................................2-22

Table 2-6 - Progress of Critical SSERP Tasks ......................................................................................2-23

Table 2-7 – SSERP Capital Expenditures..............................................................................................2-24

Table 2-8 – SSERP Capital Projections .................................................................................................2-24

Table 2-9 – Basin Schedule .....................................................................................................................2-26

Table 2-10 – Progress of LCERP Tasks ................................................................................................2-27

Table 2-11 – LCERP Capital Expenditures............................................................................................2-28

Table 2-12 – LCERP 10-Year Capital Projections (in millions)...........................................................2-28

Table 3-1 – Permitted Flow Capacity of LVSWWTF...............................................................................3-1

Table 3-2 – Permitted Organic Capacity of LVSWWTF .........................................................................3-2

Table 3-3 – Historical Influent Flow, Population Data and Rainfall Data for LVSWWTF ..................3-6

Table 3-4 – Estimated Wastewater Reductions through Conservation ...............................................3-9

Table 3-5 – LVSWWTF Dry Weather Flows Predicted by the Collection System Model ...............3-10

Table 3-6 – Monthly Effluent Ammonia Limits for LVSWWTF ............................................................3-16

Table 3-7 – Monthly Metals Limits for LVSWWTF ................................................................................3-17

Table 3-8 – Budgeted Amounts for Capital Projects at LVSWWTF (in millions)..............................3-19

Table 3-9 – Budgeted Amounts for Extraordinary O&M Projects at LVSWWTF (in thousands) ...3-19

Table 3-10 - JDPWRF Dry Weather Flows Predicted by the Collection System Model .................3-19

Table 4-1 - Projected Future Flows for BSPS Capacity .......................................................................4-19

Table 4-2 - Digester Characteristics........................................................................................................4-19

Table 4-3 - Annual Average Flow and Digester Retention Time ........................................................4-19

Table 4-4 – Number of Digesters On-line...............................................................................................4-19

Table 4-5 – Annual Average Digester Capacity ....................................................................................4-19

Table 4-6 – Volatile Solids Loading Rates to Digesters .......................................................................4-19


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Table 4-7 – Volatile Solids Reduction in Digesters ...............................................................................4-19

Table 4-8 – Volatile Solids Reduction in Individual Digesters .............................................................4-19

Table 4-9 – Future Digester Capacity Needs.........................................................................................4-19

Table 4-10 – Volatile Solids Loading Rates to the FSBs .....................................................................4-19

Table 4-11 – Future Capacity of Facultative Sludge Basins (FSBs) ..................................................4-19

Table 4-12 – Mass Balance of Solids in the FSBs ................................................................................4-19

Table 4-13 – Annual Amounts of Sludge Injected on DLDs ................................................................4-19

Table 4-14 – Area of FSBs and Lagoons ...............................................................................................4-19

Table 4-15 – Annual Rainfall at Nixon Power Plant – Base Weather Station ...................................4-19

Table 4-16 – Capacity Analysis of Supernatant Lagoons ....................................................................4-19

Table 4-17 – Annual Average Total Volatile Solids Reduction at SHDF ...........................................4-19

Table 4-18 –Maximum Concentration of Metals in ’95-’99 Permit ......................................................4-19

Table 4-19 –Maximum Concentration of Metals ....................................................................................4-19

Table 4-20 – Maximum Conc. of Metals when DLDs < 150 Meters ...................................................4-19

Table 4-21 – Metals Sample Data from Biosolids .................................................................................4-19

Table 4-22 – Budgeted Amounts for Capital Projects at SHDF (in millions) .....................................4-19


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FIGURES

Figure ES-1 – 10-Year Capital Budget for Wastewater Projects ..........................................................xiii

Figure 1-1 – Overview of Wastewater System ........................................................................................1-1

Figure 1-2 - Collection System Basins and Service Territory Boundary..............................................1-2

Figure 1-3 - Collection Mains 9” and Larger ............................................................................................1-3

Figure 1-4 - Lift Stations in the Service Area of JDPWRF .....................................................................1-4

Figure 1-5 - Lift Stations in the Service Area of LVSWWTF..................................................................1-5

Figure 1-6 - Collection System Growth over the Past 100 Years .........................................................1-6

Figure 1-7 - Major Wastewater Treatment Facilities...............................................................................1-7

Figure 1-8- J.D. Phillips Water Reclamation Facility ..............................................................................1-8

Figure 1-9 - J.D. Phillips Water Reclamation Facility .............................................................................1-9

Figure 1-10 - Las Vegas Street Wastewater Treatment Facility .........................................................1-10

Figure 2-1 – Wastewater Pipe Locations in Colorado Springs .............................................................2-1

Figure 2-2 – Manhole Locations and Creeks in Colorado Springs.......................................................2-2

Figure 2-3 – Typical Hydrograph – Plots Wastewater Flow with Time ................................................2-3

Figure 2-4 – Landuse in Unsewered Areas within the Service Territory (2008).................................2-9

Figure 2-5 – Landuse in Unsewered Areas within the Service Territory (2030)...............................2-10

Figure 2-6 - Total Stoppages by Year Through October, 2008...........................................................2-13

Figure 2-7 – Locations of Potential Improvement Projects ..................................................................2-15

Figure 2-8 – SSERP Work Management................................................................................................2-19

Figure 2-9 – Trend Analysis of Releases through Time.......................................................................2-23

Figure 2-10 – Stoppages by Year (through March, 2008) ...................................................................2-28

Figure 2-11 – TV Camera of Pipe with Grease vs. Pipe with no Grease ..........................................2-33

Figure 3-1 – Historical Annual Averages for CBOD Data for the LVSWWTF.....................................3-3

Figure 3-2 – Historical Monthly Averages for CBOD5 Data for LVSWWTF ........................................3-4

Figure 3-3 – Comparison of Influent Flow and Organic Loading for LVSWWTF ...............................3-5

Figure 3-4 – Historical Population and Influent Flow Data for LVSWWTF..........................................3-7

Figure 3-5 – Influent Flow vs. Annual Rainfall for LVSWWTF ..............................................................3-8

Figure 3-6 – Cumulative Miles of Lined Pipes vs. Flow and Rainfall for LVSWWTF ........................3-8

Figure 3-7 – Historical Population, Influent Flow Data and Future Predictions ................................3-11

Figure 4-1 – Sludge Pipeline Connecting LVSWWTF and SHDF ......................................................4-19

Figure 4-2 – Solids Handling Facility.......................................................................................................4-19


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Figure 4-3 – Comparison of Monthly Average Influent Flows between SHDF and LVSWWTF ....4-19

Figure 4-4 – Volatile Solids Loading Rate to Digesters ........................................................................4-19

Figure 4-5 – Reduction of Total Volatile Solids in Digester 8 (2001-Oct. 2008) ...............................4-19

Figure 4-6 – Annual Average Volatile Solids Reduction in Digesters ................................................4-19

Figure 4-7 – Volatile Solids Loading Rate to FSBs ...............................................................................4-19

Figure 4-8 – Mass Balance – Tons of Accumulated Tons of Solids in FSBs....................................4-19

WASTEWATER INTEGRATED MASTERPLAN EXECUTIVE SUMMARY

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EXECUTIVE SUMMARY

The Wastewater Integrated Masterplan (WWIM) is a dynamic planning and implementation tool that evaluates all systems related to wastewater. The plan makes recommendations for the expansion and maintenance of the wastewater system in an innovative, cost-effective and environmentally responsible manner. Capacity assessments for major wastewater system components are performed to guide planning for capital projects.

Each of the proposed projects undergoes an extensive alternative analysis process that evaluates the issues and determines the need for and timing of improvements. These analyses are re-evaluated and documented annually with a new version of the WWIM.

The WWIM is arranged in four sections. Section 1 presents an overview of the wastewater system components. Section 2 describes and analyzes the collection system and lists capital costs for the next 10 year period. Section 3 covers the wastewater treatment facilities consisting of the J.D. Phillips Water Reclamation Facility and the Las Vegas Street Wastewater Treatment Facility. Section 4 examines the Solids Handling and Disposal Facility.

The executive summary below gives a high level overview of the facilities, capacity issues, the most pressing regulatory issues, and a brief description of major capital projects. Annual budgeted amounts for capital projects in the wastewater system for the 10-year planning period from 2009 to 2018 are also presented.

ES 1. Collection System Masterplan

Springs Utilities has the largest single-operator sanitary sewer system in Colorado. To collect and


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convey the wastewater generated by the residential and commercial customers, Springs Utilities owns and operates over 1,600 miles of gravity main, 13 miles of force main, and 19 lift stations.

Capacity: As development continues in the City of Colorado Springs, wastewater flows are added to collection pipes. A computer model of the collection system has been developed that allows the capacity of all large diameter sewer mains to be assessed. As new development triggers the permitting process, flows from the new development are modeled to see if any downstream sewer pipe capacity issues will occur. The computer model helps Springs Utilities be proactive in preventing sewage spills that can come from too much sewage being routed through a given pipe. It also allows for proactive planning to upsize pipes as development occurs.

Regulatory Challenge: Continued adherence with the Colorado Department of Health & Environment’s (CDPHE) compliance order is the major challenge facing the collection system. Efforts to reduce sanitary sewer overflows (SSOs) will continue. Great progress over the past seven years has been made towards reducing the number of SSOs that occur in Colorado Springs.

Collection Programs: Sanitary sewer systems are among the largest infrastructure investments that are made by communities. As such, it is imperative that these systems are managed, operated and maintained in a manner that maximizes their serviceable life. In addition to preserving the value of public infrastructure, it is critical that sanitary sewer agencies minimize overflows from these systems. Overflows of domestic and industrial wastes can pose a substantial risk to public health and environment. National and State regulatory and enforcement attention toward SSOs has been increasing over the past several years.

Five program areas have been developed to address assessment of collection system components, and based on the findings rehabilitate or replace components as necessary. Since the year 2000, Springs Utilities has spent over $97,000,000 on capital related work to improve its collection system.

1) Sanitary Sewer Evaluation and Rehabilitation Program (SSERP) - The SSERP is focused on the evaluation and repair of wastewater pipe segments larger than eight inches in diameter, lift stations, and other critical infrastructure. This program is nearing completion.

2) Local Collectors Evaluation and Rehabilitation Program (LCERP) – The LCERP was instituted to assess and rehabilitate the majority of the collection system made up of wastewater pipe segments eight inches and smaller in diameter.

3) Sanitary Sewer Creek Crossings Program (SSCC) – The SSCC addresses wastewater pipes that cross creeks and those that run parallel to creeks, as these pipes may be vulnerable to bank movement during high flows. Some of the creeks have very unstable banks and stream beds that require frequent assessment for impacts to sewer infrastructure. The first pass of this program is scheduled for completion in 2012.


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4) Manhole Evaluation and Rehabilitation Program (MHERP) – focused on assessing the condition of manholes and then rehabilitation or replacement of manholes as needed.

5) Collection System Rehabilitation and Replacement Program (CSRRP) - Each of the programs listed above (numbers 1-4) provide a first pass condition evaluation and capital rehabilitation, repair and replacement of vulnerable collection system infrastructure. Since an ongoing monitoring, evaluation, and rehabilitation program is required to maintain the collection system, the CSRRP addresses this need.

6) Sanitary Sewer Creek Crossing Rehabilitation and Replacement Program – when the first pass of work is completed on creek crossing and pipes paralleling the creeks, a long term program to provide ongoing assessment and maintenance is needed. This program will be initiated in 2013 after the first pass is completed in 2012.

Capital Projects Budget: Table ES-1 and Figure ES-1 presents the 10-year capital budget for the collection system programs.

Table ES-1 – 10 Year Capital Budget for Collection System Projects (in millions)

Projects 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018

SSERP – mains larger than 8”

$3.33 $0.42 $0.0 $0.0 $0 $0 $0 $0 $0 $0

LCERP – mains 8” and smaller

$7.38 $8.54 $10.3 $10.1 $9.47 $9.19 $8.97 $9.35 $6.70 $7.92

Creek Crossings $8.35 $8.78 $7.18 $5.73 $0 $0 $0 $0 $0 $0

Manhole Program $1.24 $1.31 $1.41 $1.44 $0.91 $0.95 $1.00 $1.05 $1.10 $1.16

Long Term Collection System Rehab.& Repl.

$1.75 $2.26 $2.15 $1.81 $1.75 $1.46 $1.07 $1.03 $1.64 $1.28

Long Term Creek Crossing Rehab.

$0 $0 $0 $0 $3.61 $3.79 $3.98 $4.17 $4.38 $4.60

Total $22.0 $21.3 $21.0 $19.1 $15.7 $15.4 $15.0 $15.6 $13.8 $15.0

ES 2. Wastewater Treatment Facilities Masterplan

Colorado Springs Utilities owns and operates two wastewater treatment plants. The northern area of Colorado Springs is served by the J.D. Phillips Water Reclamation Facility (JDPWRF). The rest of the city is served by the Las Vegas Street Wastewater Treatment Facility (LVSWWTF).

Capacity: The JDPWRF started treating wastewater in May 2008. It currently treats seven million gallons per day (mgd) and has a rated capacity of 20 mgd. The LVSWWTF currently treats approximately 36 mgd and has a rated capacity of 65 to 75 mgd (reduced capacity in winter months). Both facilities have more than adequate treatment capacity for the next 10 years. However, at the LVSWWTF during the next several years when flows are reduced due to JDPWRF picking up some of the treatment burden, a window of opportunity exists to make upgrades to the secondary treatment process at the LVSWWTF. The secondary treatment system is a biological process that further removes pollutants from the wastewater. This process occurs by holding the wastewater in tanks


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and adding microorganisms that are cultivated to absorb the pollutants from the wastewater. Currently four out of five secondary tanks are needed. In 2006 and 2007 all five tanks were needed. Upgrades to the secondary treatment process will allow more phosphorous, ammonia and organic matter to be removed.

Regulatory Challenge: With operating permit renewals that occur every five years, new effluent limits will continue to provide new operating goals for the plants to meet. The 2011 permit renewal for LVSWWF is expected to require compliance with lower ammonia effluent limits. The 2011 permit is also going to change the disinfection indicator organism from fecal coliforms to E. coli with significantly lower limits for E. coli.

Capital Projects: The JDPWRF is a brand new plant and therefore capital projects are unnecessary in the near term. The major capital projects planned for the LVSWWTF include the following:

1) Disinfection System – The current chlorine disinfection system will need to have significant upgrades made to it for the plant to meet new 2011 permit requirements. Springs Utilities conducted an alternatives analysis in 2008 in which key objectives such as safety, ease of operation, regulatory burden, reliability, life-cycle costs, etc were scored for each alternative. The alternatives included installation of a new ultra-violet light (UV) disinfection system, an ozone system, sodium hypochlorite system and upgrading of the existing chlorine system. The best option was an UV system to replace the chlorine system. Design of the UV system will begin in 2009 with construction taking place in 2009 and 2010.

2) Secondary Treatment Improvements – Design and construction of improvements to secondary treatment at LVSWWTF will begin in 2010 and continue through 2013.

3) Primary Backup Pump Replacement – Pumps are needed in the middle of the plant to lift effluent from the primary sedimentation tanks (PSTs) to a channel that allows wastewater to flow by gravity through the rest of the plant. The pumps are a critical component at the plant. The existing backup pumps are old, have a limited range of function, and foundation settlement has compromised their reliability. Replacement of the pumps with pumps that are equipped with variable speed drives will increase the reliability and functionality of these critical backup pumps.

4) Grease Concentrator – The grease concentrator is a large tank in which grease is allowed to separate from water to concentrate it. In 2008 upgrades to the headworks at LVSWWTF were made that included new screens for debris and grit and new rags and grit handling systems. The grease concentrator upgrade is the last piece of the upgrades that needs to be completed.

5) Sky Flume Concrete Repair – The Sky Flume is the elevated channel from which wastewater can flow by gravity through the rest of the plant. A tremendous amount of hydrogen sulfide is stripped from the wastewater in the outfall structure of the Sky Flume and is treated by an odor control system. Inside the Sky Flume, the hydrogen sulfide is converted by bacteria on concrete surfaces to sulfuric acid that attacks the concrete. The underside of the concrete lid of the outfall structure has been degraded by sulfuric acid to the point where it needs to be removed and replaced with a cover that is inert to acid attack.


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6) Small miscellaneous projects - This category includes small capital projects such as roof replacements, hydrant replacements, building improvements, vehicles and equipment. Small capital projects such as these are not discussed in detail, because the WWIM is focused on major capital projects. The total for small capital projects appear in Table ES-2 under the “Small Projects and Building Maintenance” category

The budgeted amounts for capital projects at LVSWWTF are presented in Table ES-2 and Figure ES-1.

Table ES-2 – Budgeted Amounts for Capital Projects at LVSWWTF (in millions)

Projects 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018

Disinfection $1.35 $9.75 $0.97 $0 $0 $0 $0 $0 $0 $0

AWT Improvements $0 $0 $0 $1.00 $5.20 $5.00 $3.72 $0 $0 $0

Primary Pump Replacement

$0.25 $0.25 $0 $0 $0 $0 $0 $0 $0 $0

Grease Concentrator $0.70 $0 $0 $0 $0 $0 $0 $0 $0 $0

Sky Flume Concrete Repair

$0.35 $0 $0 $0 $0 $0 $0 $0 $0 $0

Small Projects & Building Maintenance

$0.24 $0.19 $0.95 $0.04 $0.32 $0.30 $0.19 $0.14 $0.30 $0.60

Total $2.89 $10.2 $1.92 $1.04 $5.52 $5.30 $3.91 $0.14 $0.30 $0.60

ES 3. Solids Handling & Disposal Masterplan

Located 17.6 miles southwest of downtown Colorado Springs on the 5,000 acre Clear Spring Ranch, the Colorado Springs Utilities’ Solids Handling & Disposal Facility (SHDF) collects, stabilizes, stores, and disposes of all sewage sludge (biosolids) produced at the Las Vegas Street Wastewater Treatment Facility (LVSWWTF) and the J.D. Phillips Water Reclamation Facility (JDPWRF). A 17.5 mile pipeline conveys the sludge to a digester complex at SHDF where the biosolids undergo digestion and then stabilization in Facultative Sludge Basins (FSBs). Stabilized sludge is injected on dedicated land disposal units (DLDs) for final disposal.

Capacity: In order to evaluate capacity issues at SHDF, assessments of the digesters, FSBs, and DLDs need to be undertaken. Currently five of eight digesters are in operation, and based on current projections, a sixth digester will not need to be put into service until 2014. However, four of the digesters are old and in need of significant rehabilitation work. This work will need to be completed before the old digesters can be counted on to provide reliable capacity.

Design loading rates for the FSBs are projected to be exceeded in 2015. The FSBs currently are storing a backlog of solids because of several years when weather conditions reduced time frames for biosolids injection on DLDs. In addition some DLD acreage on the western property boundary was restricted from sludge injection from 2006 to 2008. The regulatory issue requiring the offset has been resolved and some of this acreage can go back into service. This acreage will help reduce some of the solids backlog in the FSBs.


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For DLD capacity, in addition to the western DLD acreage that can be put back into service, the opening of a new DLD area will help increase injection rates to reduce the backlog of biosolids in the FSBs. Construction work has started on DLD #17 and should be completed.

Regulatory Challenge: In 2008, the CDPHE began promulgating new impoundment regulations for solid waste impoundments. The impoundment regulations are expected to be finalized in early 2010. The impoundment regulations may affect the FSBs, supernatant lagoons, and stormwater pond behind the retention dam. Liners and leak detection systems may be required to be installed for some or all of these impoundments. The financial impact if the FSBs, lagoons and stormwater pond need to be lined will be very large.

Capital Projects: Major capital projects planned for the SHDF include the following:

1) Digester Cover Replacement and Equipment Rehabilitation – The top priority for capital expenditure in the next 10 years is to rehabilitate the four old anaerobic digesters. Although the digester complex has excess hydraulic capacity until at least 2014, the old digesters have components that are reaching the end of their useful life. Replacement of the floating covers and other components will need to be carried out before the old digesters can be counted on for reliable capacity.

2) Expansion of FSBs – under current future flow projections, the FSB loading rate will exceed the design loading rate in 2015. Design work is scheduled to start in 2014, with construction of two additional FSBs in 2015. Expansion of the FSBs may need to be moved up if the amount of solids that have recently accumulated in the FSBs cannot be reduced in a timely fashion, or if wet weather years occur frequently.

3) Expansion of DLD #17. Work was started on construction of DLD #17 in 2007. Due to budget constraints, work was not continued in 2008. The FSBs are currently holding an excess amount of solids due to the fact that injection rates to the DLDs were low during 2002 to 2004 due to bad weather and reduction of DLD acreage because of a regulatory issue. Most of the previously restricted DLD acreage will be put back into service in 2009. If construction of DLD #17 can be completed in 2009, the additional acreage will help increase injection of biosolids and reduce the backlog of solids in the FSBs.

The budgeted amounts for capital projects at SHDF are presented in Table ES-3 and Figure ES-1. Budget amounts for the impact from new impoundment regulations have not been developed yet because the scope of the regulations is still in the development phase.

Table ES-3 – Budgeted Amounts for Capital Projects at SHDF (in millions)

Project 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018

Digester Covers $0.1 $0.41 $3.55 $2.75 $0 $0 $0 $0 $0 $0

FSB Expansion $0 $0 $0 $0 $0.0 $0.36 $3.27 $0 $ $0

DLD #17 $0.15 $0 $0 $0 $0 $0 $0 $0 $0 $0

Various Small Projects $0.11 $0 $0 $0.0 $0.04 $0 $0 $0 $0 $0

Total $0.26 $0.41 $3.55 $2.75 $0.04 $0.36 $3.27 $0 $0 $0


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10-Year Proposed Wastewater Capital Budget

0

5

10

15

20

25

30

35

40

2009 2010 2011 2012 2013 2014 2015 2016 2017 2018

Year

Co

st (

Mill

ion

s $)

Collection

Treatment

Figure ES-1 – 10-Year Capital Budget for Wastewater Projects

WASTEWATER INTEGRATED MASTERPLAN OVERVIEW OF WASTEWATER SYSTEM

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1. OVERVIEW OF WASTEWATER SYSTEM

This section of the report provides an overview of Colorado Springs Utilities’ existing wastewater infrastructure and facilities. With 322,770 people, the City of Colorado Springs (City) is the largest city in El Paso County and the second largest city in Colorado. Colorado Springs is bounded by Black Forest and Monument on the north and the Rocky Mountains on the west. Springs Utilities provides wastewater services for the City of Colorado Springs and other areas that are approved by the City Council for the City of Colorado Springs (City Council). To date, City Council has approved long term contracts for areas including Peterson Air Force Base, Manitou Springs, and Stratmoor Hills Water and Sanitation District. As of May 2008, Springs Utilities provided wastewater service to 128,563 customers (121,798 residential customers, 6,765 commercial customers).

Figure 1-1 provides an overview of the wastewater system. Wastewater begins its journey from homes and businesses located in wastewater basins. Interceptors or collection mains route flow to treatment plants. The biosolids removed from the wastewater at the plants are treated at a solids handling facility. At some locations in the collection system, wastewater reaches a low point at which a lift station pumps the wastewater back up to a point where it can flow by gravity.

Figure 1-1 – Overview of Wastewater System



1.1. Collection System

Wastewater flow comes from five major basins, Monument Creek, Spring Creek, Sand Creek, Stratton Meadows and Jimmy Camp Creek. The Monument Creek Basin has been split into upper and lower sub-basins. This is because the recently constructed J.D. Phillips Water Reclamation Facility started treating wastewater generated by the Upper Monument Creek Basin. The basins along with the current service territory boundary are shown on Figure 1-2.

To collect and convey the wastewater generated by the residential and commercial customers in these basins, Springs Utilities owns and operates over 1,600 miles of gravity main and 13 miles of force main. Collection mains with diameters larger than nine inches are shown on Figure 1-3.

Force mains are used when, due to local topography, an area cannot be served entirely by gravity. Nineteen lift stations are used to transfer the wastewater from these areas to adjacent basins to convey wastewater by gravity to the treatment facilities. The lift stations in the service area for the J.D. Phillips Water Reclamation Facility (JDPWRF) are shown on Figure 1-4.

Figure 1-2 - Collection System Basins and Service Territory Boundary



Figure 1-3 - Collection Mains 9” and Larger



Figure 1-4 - Lift Stations in the Service Area of JDPWRF

The lift stations in the service area for the Las Vegas Street Wastewater Treatment Facility (LVSWWTF) are shown on Figure 1-5. Most of the lift stations consist of pumps located in



underground vaults. The Sand Creek Lift Station is the largest one and is housed in its own building.

Figure 1-5 - Lift Stations in the Service Area of LVSWWTF



Figure 1-6 shows how the collection system has grown over the past 100 years. The current wastewater service territory is also shown for reference. The growth in the past 50 years is impressive.

Figure 1-6 - Collection System Growth over the Past 100 Years

1905 1955

1980 2005

21 Miles of Pipe 195 Miles of Pipe

787 Miles of Pipe 1524 Miles of Pipe



1.2. Treatment Facilities

Springs Utilities treats an average of nearly 42 million gallons of wastewater per day (mgd). Wastewater generated by the service area flows to one of two treatment facilities that are owned and operated by Springs Utilities. Both facilities discharge treated effluent to the creek and pump the remaining sludge 17.6 miles south to Clear Spring Ranch Solids Handling & Disposal Facility (SHDF) where further processing and land application of the processed biosolids takes place. The locations of the three main wastewater treatment facilities are shown on Figure 1-7.

Figure 1-7 - Major Wastewater Treatment Facilities



Wastewater generated from the northern portion of the Monument Creek Basin is treated through primary, secondary and tertiary processes at the new J.D. Phillips Water Reclamation Facility (JDPWRF). Photos of JDPWRF are shown on Figure 1-8 and 1-9. JDPWRF currently has a 20 million gallon per day (mgd) capacity and is expandable to 30 mgd. The JDPWRF will treat approximately 7 mgd during its first year of operation (2008).

The LVSWWTF currently treats the wastewater from all the basins shown on Figure 1-2 except for the Upper Monument Creek Basins. Treatment of the wastewater occurs in three stages. Primary treatment consists of settling tanks where grit and solids are removed. Secondary treatment makes use of microorganisms to clean up the wastewater. Solids removed at LVSWWTF are pumped to SHDF. In tertiary treatment wastewater is disinfected using chlorine. Water that is re-cycled for non-potable use is filtered and disinfected. Non-pot water used by the Drake Power Plant has ammonia removed from it. Photos of the LVSWWTF are shown on Figure 1-10.

Figure 1-8- J.D. Phillips Water Reclamation Facility



Figure 1-9 - J.D. Phillips Water Reclamation Facility


PAGE 1-10 DRAFT – Dec. 31, 2008

Figure 1-10 - Las Vegas Street Wastewater Treatment Facility


PAGE 1-11 DRAFT – Dec. 31, 2008

1.3. Biosolids Facility (SHDF)

The Clear Spring Ranch Solids Handling and Disposal Facility processes biosolids from JDPWRF and from LVSWWTF. The solids from JDPWRF are conveyed through the collection system to LVSWWTF where they are combined with the LVSWWTF solids. A 17.6-mile pipeline from LVSWWTF then conveys all solids to the Solids Handling & Disposal Facility (SHDF) at Clear Spring Ranch (see Figure 1-6 for pipeline and facility location). At the SHDF, the solids pass through an anaerobic digestion process and are stored in basins where further treatment takes place. The biosolids are then pumped from the basins and injected below the soil surface in fields (dedicated land disposal units or DLDs). The land disposal units are located behind a dam that prevents any runoff or groundwater from leaving the disposal site. The SHDF facility is a zero-discharge facility meaning all liquids on the site must be contained on the site and not allowed to be conveyed to any external water sources. The only means of reducing water on the site is through evaporation.

1.4. Future Development

Future development in the City of Colorado Springs will occur mostly to the north and east. The northern area includes numerous large developments that are currently under construction such as Flying Horse Ranch and Wolf Ranch. On the eastern edge of the city is Banning Lewis Ranch which was annexed in 1988 and is 24,311 acres located east of Marksheffel Boulevard in the Jimmy Camp Creek Wastewater Basin (see Figure 1-2). The annexed area comprises approximately half of the Jimmy Camp Creek Basin and is delineated by the service territory boundary.

The first development in the annexed area began in 2006 and is located in the northwest corner of Banning Lewis Ranch. At build-out the annexed area is projected to increase the population of Colorado Springs by an estimated 190,250 people; a 40% increase of its 2008 population.

At this time the location of wastewater treatment for the Jimmy Camp Creek wastewater basin is being analyzed and negotiated with the majority landowner of Banning Lewis Ranch.

WASTEWATER INTEGRATED MASTERPLAN COLLECTION SYSTEM MASTERPLAN


2. COLLECTION SYSTEM MASTERPLAN

Springs Utilities operates a sanitary sewer collection system that includes approximately 1,600 miles of sewer and more than 32,000 manholes. Wastewater pipes with a diameter larger than eight inches are shown in Figure 2-1. Also included in Figure 2-1 is a schematic showing wastewater pipes with a diameter eight inches and smaller.

Figure 2-2 shows the general location of approximately 32,000 manholes. A general schematic of the creeks in Colorado Springs is also shown. Locations where wastewater pipes cross the creeks have provided a major challenge in recent years.

Figure 2-1 – Wastewater Pipe Locations in Colorado Springs

In this section, wastewater collection system modeling is described. A computer model of the collection system has been built that allows the Utilities to check the capacities of pipes against future needs. Identification of undersized pipes leads to their timely replacement with larger pipes and prevents sanitary sewer overflows (SSOs) from occurring.



Figure 2-2 – Manhole Locations and Creeks in Colorado Springs

Wastewater Programs are also discussed in this section and were initiated to systematically inspect, assess, prioritize, repair, rehabilitate and replace wastewater infrastructure. These programs address the physical infrastructure above and below ground. Every year Springs Utilities inspects miles of pipe and hundreds of manholes utilizing Closed Caption Television (CCTV) cameras. These inspections allow internal engineers to assess and prioritize infrastructure that needs repair, rehabilitation or replacement using nationally accepted methodology. A critical part of Wastewater Programs is the inspection, assessment, prioritization and rehabilitation of pipes in and near creeks. In the dynamic creek environment, infrastructure needs special protection against erosion caused by storm events and increased run-off resulting from development.

2.1. Wastewater Collection System Modeling

An extensive sewer system capacity evaluation of the interceptors, trunk sewers, and major lift stations in the Springs Utilities collection system was completed in 2006. The evaluation included development and calibration of a dynamic hydraulic model, computation of peak flows in all major sewers and lift stations, identification of current and



future capacity deficiencies, and development of capital improvements to address those deficiencies through the year 2025.

The hydraulic model was integrated with Springs Utilities’ Facility Information Management System (FIMS), an ESRI-based GIS, to facilitate initial model creation as well as future model updates. Elevation surveys and manhole inspections covering virtually all of the modeled sewers were conducted and input to FIMS, ensuring an accurate representation of the existing sewer system and pipe capacities in the model. A custom GIS application was developed that utilizes the best available databases of City, County, and Regional planning information as well as customer water and wastewater meter records as the basis for generating accurate and updateable wastewater flow estimates and projections for the model.

2.1.1. Hydraulic Model Development The wastewater collection system model is called InfoWorksCS, which is a fully dynamic hydraulic modeling software package developed by Wallingford Software. By way of an overview, to build the model, piping system information is entered which includes pipe diameters, lengths, elevations, and manholes. Next, sewersheds are defined. A sewershed is a drainage area that collects sewage to a single outfall. For each sewershed, flow rates from the residential population, commercial buildings, and estimated inflow and infiltration rates are estimated. From this information the model generates a flow from each sewershed and combines them into an overall system hydrograph.

Figure 2-3 – Typical Hydrograph – Plots Wastewater Flow with Time



A hydrograph is a plot of flow over time. A typical wastewater hydrograph (see Figure 2-3) will show two peaks, one that occurs in the morning and one that occurs in the evening. The peaks correspond to periods of higher water use rates of people getting up in the morning and conducting household activities in the evening.

Hydrographs are generated for dry flow and wet weather flow. Wet weather flow is generated in the model by introducing a storm event that the model then takes into account in generating the hydrograph. The model compares peak flows to the hydraulic capacity of sewer pipes and flags any pipes that have capacity issues.

2.1.1.1. Input of Pipe Characteristics and Manholes Springs Utilities maintains a Geographic Information System (GIS) database with information on its distributed assets, referred to as the Facility Information Management System (FIMS). FIMS provided the primary source of data describing the spatial coordinates and physical characteristics of the manholes and pipes that were included in the model. Attributes obtained from FIMS included manhole rim elevation and pipe diameter, length, and upstream and downstream invert elevations, as well as the unique identifiers (Local Identification Numbers - LIDs) for each manhole and pipe. These LIDs are retained through the modeling process to facilitate the exchange of data between InfoWorks and FIMS. InfoWorksCS includes integrated database files that must be populated with the sewer attributes needed for modeling. The software includes data import routines that were used to import FIMS data into the InfoWorks data files.

The InfoWorksCS model consists of all pipes 10-inches in diameter or larger (collectors, trunk sewers, and interceptors), as well as selected 8-inch pipes required to maintain network connectivity. These larger pipes represent approximately 40 percent of the collection system by length, and include about 12,325 manhole-to-manhole pipe segments amounting to 622 miles of pipe. The model also includes the 13 largest pump stations.

2.1.1.2. Lift Stations and Force Mains Lift stations were modeled by two different methods. For the Kettle Creek and Sand Creek Lift Stations, the model includes the head/discharge curves for each pump unit, and the force mains are explicitly modeled. During each modeling time step, the model computes the discharge from each pump unit from its pump curve, considering the static head differences between the water level in the wet well and the force main discharge manhole, and the head loss in the force main. The wet well dimensions are used to determine the change in water level in each time step, and individual pump units are cycled on and off using the same on/off levels actually used to operate the lift stations. This is the most realistic representation possible in InfoWorks, and was used for these two larger lift stations having multiple duty pumps. The other lift stations were represented in the model using fixed-discharge pumps. In this representation, the discharge from each pump unit is assumed to be constant at a specified discharge capacity. As with the other two lift stations, the pumps are cycled on and off based on changes in wet well water levels, although most of these stations have a single duty pump. Basic lift station and force main descriptive information is summarized in Table 2-1.



Table 2-1 – Lift Station Data

Wastewater Pump Station\Force Mains

Year Constructed

Pump Station

Capacity (MGD)

Force Main

Diameter (inches)

For Main Material

Force Main

Length (feet)

Airport Business Park 2008 1.2 10 HDPE 5300

Big Valley 1978 0.14 4 DIP 410

Bison Ridge 2004 0.72 6 PVC 2000

Black Squirrel 1987 0.72 8 PVC 2200

Chapel Hills 1982 0.72 8 PVC 5350

Cheyenne 1952 0.5 6 CIP 395

Coronado 1973 0.22 6 DIP 850

Drennan 1994 1 10 PVC 5400

Janitell 1997 0.2 4 PVC 1140

JL Ranch 2007 0.84 8 PVC 3200

Kettle Creek 1987 2.5 12 DIP 5800

Middle Tributary 1990 2 12 DIP 8500

Monument Branch 2000 2 16 DIP 3500

Pando 1952 0.5 6 CIP 0

Peregrine 1987 0.5 6 PVC 2820

Sand Creek 2002 15 36 HDPE 19000

Smith Creek 2007 0.3 4 PVC 1900

Stratton Meadows 1997 3 16 DIP 1060

Talon Ridge 2004 0.184 4 PVC 550

Total 69,375

2.1.1.3. Land Use/Population Estimating An important step in building the InfoWorksCS model involves estimating the populations for each of the sewersheds. This section details the process that was undertaken.

2.1.1.3.1. Existing Land Use/Population Estimating existing population in each sewershed involved distribution of the 2000 census data to sewersheds and then updating the populations based on land use data. A simple area-weighted polygon intersection process was initially proposed for distributing the 2000 census populations from census blocks to sewersheds. However, there are several outlying census blocks that are considerably larger than average and therefore stretch across multiple sewersheds. To minimize this problem, the census blocks were first intersected with the City and County land use files, and the population was distributed only



to the developed residential lands within the block, and in proportion to the estimated average population density of each land use category.

2.1.1.3.2. Buildout Land Use/Population (Residential) Buildout refers to the condition in which every lot in a sewershed has a house on it. Population projections were used as the basis for computing buildout residential dry weather flows. Dry weather flows occur when no storm event is taken into account. The buildout population in each sewershed was computed by adding additional projected population (based on future land uses and population densities) to the “existing” 2008 populations. The City had last updated the projected land uses for vacant areas in 2002, so Montgomery Watson-Harza, Inc. (MWH) updated it to 2008 by eliminating areas that have developed based on the City’s 2004 existing land use file. The residential land use categories specified in the City’s future land use file are the same as those in the existing land use files, so the additional population to buildout could be computed using the population densities from the existing developed urban area.

2.1.1.3.3. Buildout Land Use/Population (Non-Residential) The existing non-residential flows were also used as the starting point for the 2008, 2020, and 2030 scenarios. Additional non-residential flows in each sewershed from 2008 to 2030 were computed by multiplying the future acreage in each non-residential land use category from the City future land use file (i.e., commercial, office, and industrial) and the County land use file (assigned to equivalent City uses of commercial, office, and industrial) by per-acre flow factors. The underlying assumption is that all future increases in non-residential flow will come from development of vacant lands planned for non-residential development. As is the case for residential development, this assumption is reasonable given that the vacant land has much more than enough capacity to absorb the projected increase in employment through 2030, without densification. Densification refers to redevelopment of existing areas. For example an old two story building is demolished and replaced with a new five story building.

2.1.1.4. Model Calibration The dry weather flow calibration involved running the model to determine the per-capita residential unit flow rates and 24-hour weekday and weekend diurnal flow profiles that best matched monitored flows throughout the system. Since non-residential flows were based on water consumption data, no calibration was needed for non-residential flow rates. The calibration also involved determining the amount of groundwater infiltration (GWI) present in each metered area during the flow monitoring periods. The specific days selected for the calibration were two typical weekdays and two typical weekend days during dry weather, preceded by several days with no rainfall.

Initial calibrations were performed for the Cottonwood Creek Basin against the 2000 temporary flow monitoring data, and the Sand Creek Basin against the 2001 temporary flow monitoring data. These model runs assumed the 2000 population estimates. Following these calibrations, the entire system was modeled using 2002 populations to calibrate the rest of the system against the 2002 temporary flow monitoring data. Since 2002 was a very dry year compared to 2000 and 2001, the GWI rates determined in the 2000 and 2001 calibrations were reduced to match 2002 conditions. Overall, the dry weather calibration yielded excellent results



Flow meter and rain data were reviewed to determine which events would be suitable for wet weather model calibration. When selecting calibration storm events, several factors are weighed in this decision process. First, an event should be of sufficient enough size to exhibit a response in the sanitary sewer system. Second, the events should be reviewed to ensure that a majority of the meters and rain gauges were operating during the event, so that there is data to verify against. Because of the nature of flow meters, it is sometimes difficult to have all meters operational for all the storm events. Third, to maximize the understanding of wet weather inflows, it is preferable that the basin should be exhibiting normal flow conditions before the event occurs. Fourth, if possible, rain events with different areal extents and magnitudes should be chosen to increase the robustness of the model to handle different types and intensities of storms.

To determine the amount and spatial distribution of rainfall during the calibration period, gauge-adjusted radar rainfall data were obtained from OneRain Corporation for July 10 through September 9, 2005. Four storm events, on August 1lth, August 13"', August 16' and August 20th occurred during the flow metering period, and the data is summarized in Table 2-2. Storm Events A and B resulted in very little response in the collection system. Storm A was a very long event with generally low intensities. Storm event B was a slightly shorter event with some very high intensity in some area, but system wide showed little response. Storm C was the shortest of the rainfall events over the collection system and did show a good response across most meter sites. Storm D was the largest event averaging almost one inch of rain over the entire collection system, with the largest peak intensities across the system. Storm D exceeded a 2-year 3-hour storm event in some parts of the basin. In general emphasis was placed on calibration of the model to Storm D because it: was very similar to a design storm event, but all four storms were evaluated in the model calibration.

Table 2-2 – Wet Weather Storm Event Data

Storm Event

Event Start Duration of Rainfall

Peak Intensity Single

Cell (in/hr)

Peak Depth Single

Cell (in)

Average Peak

Intensity (in/hr)

Average Depth

(in)

A 08/11/05

10:00 12 hr 50

min 0.99 1.34 0.19 0.40

B 08/13/05

17:00 8 hr 10 min 5.07 1.32 0.79 0.30

C 08/16/05

12:00 4 hr 10 min 2.05 .73 0.66 0.23

D 08/20/05

10:00 5 hr 20 min 2.61 3.92 1.32 0.97



2.1.2. Capacity Evaluation

2.1.2.1. Future Service Boundary Some portions of the study area are not expected to be sewered to either of the wastewater treatment plants (JDPWRF and LVSWWTF). These areas may remain undeveloped or may be served by individual or community systems. Planned housing densities in the County areas within the study area were a key consideration in defining the future service area boundary. The El Paso County Land Development Code allows individual water and sewer systems on lots of five acres or larger. On lots between 2.5 and 5 acres, individual systems are allowed only if certain requirements are met. Figure 2-4 shows the existing 2008 land uses in the study area along with the service territory boundary shown as a dark blue line on the figure. Areas that are already served (i.e. existing sewersheds and metered areas) are shown in the light blue shaded area in the middle of the figure. The unsewered areas that could contribute flow in the future exist between the light blue shaded area and the territory boundary. Figure 2-5 shows similar data projected for the year 2030. The data in these figures were used to identify the additional areas that should be assumed to contribute wastewater in the future.

In general, all areas in the City have been included in future sewersheds if planned for residential or non-residential development. In the County, most areas have been excluded because they are currently developed at 5-acre or larger lots, or planned to be developed at those low densities. Areas developed at or planned for 2.5-acre or smaller lots have been included in future sewersheds in most cases, and those sewersheds may include 5-acre lots that are adjacent to those higher-density lots.

There are several small areas and “islands”, both in the City and County, which are not included in existing sewersheds because they are currently on individual systems. These areas include the Woodmen Water District, Park Vista and two nearby triangular-shaped areas, and an area near Peterson AFB. It is anticipated that sewer service to these areas will be gradually implemented as existing septic tanks fail and are taken out of service.

The model was calibrated to match existing dry and wet weather flows using data from 67 temporary flow meters installed between 2000 and 2002, plus system wide data from the influent meter at the LVSWWTF. Rainfall throughout the service area during calibration storm events was quantified using the latest in radar rainfall technology. Historical flow and rainfall data were used to formulate a design storm that is estimated to generate a once-in-five-year peak wet weather flow as the basis for evaluating the sewer system capacity with the calibrated hydraulic model.



Figure 2-4 – Landuse in Unsewered Areas within the Service Territory (2008)


PAGE 2-10 DRAFT – Dec. 31, 2008

Figure 2-5 – Landuse in Unsewered Areas within the Service Territory (2030)


PAGE 2-11 DRAFT – Dec. 31, 2008

2.1.2.2. Flow Estimating Methodology This section provides an overview description of the data and methods used to estimate the wastewater flows in each modeled sewershed for the existing, 2020, 2030, and buildout scenarios. The dry weather flows are covered first, including separate discussions on flows from residential, non-residential, and groundwater infiltration sources. The wet weather flows and metered dischargers are then described.

2.1.2.3. Dry Weather Flows Dry weather flows were developed for residential and non-residential customers.

2.1.2.3.1. Existing and Future Residential Residential average dry weather flows were computed by applying per-capita unit flow factors (gpd/cap) to estimated existing and future populations in each sewershed. A basic assumption in the sewershed population projections was that all future population increases would occur in currently vacant areas planned for residential use. This assumption is reasonable given that the projected increase in population by 2030 could be more than accommodated in these areas, without densification of existing residential development. Appropriate unit flow factors were determined through model calibration to metered flows obtained during temporary flow monitoring studies.

2.1.2.3.2. Existing Non-Residential Non-residential average dry weather flows were estimated from a customer water consumption database maintained by the Springs Utilities. Monthly meter readings taken between October 1, 2002 and March 1, 2003 for all 5,500 non-residential customers (rate classes CM and CE) were processed. These cold-weather months were selected because outdoor water use is minimal and water consumption approximates wastewater production. The median of the five monthly water consumption values was taken as the best estimate of average dry weather flow. The geographic location of each customer was geo-coded based on its address pointer, allowing the individual flow values to be aggregated by sewershed for modeling. The 2002-2003 data was used for model calibration, and the flows were subsequently updated based on a 2004-2005 version of the database for use in the existing condition model.

2.1.2.4. Wet Weather Flows Infiltration/inflow (I/I) into the sewer system includes rainfall-dependent infiltration/inflow (RDI/I) and groundwater infiltration (GWI). The GWI component includes elevated GWI that is typically present in the summer wet weather season due to higher surface and groundwater levels. The RDI/I component represents a hydrograph in response to a specified rainfall event, and is additive to the GWI and dry weather flows. Calibration parameters consist of the percentage of the rainfall that enters the sewer system, and distribution of the flow into fast, medium, and slow response types (which dictate the shape and duration of the hydrographs).

2.1.2.5. Metered Flows Some special customers and outside entities that discharge wastewater into the Springs Utilities system are separately metered at the point where their flow enters the system. Existing and future flows from these areas were not estimated using population,


PAGE 2-12 DRAFT – Dec. 31, 2008

employment and land use data as described above. Instead, separate sewersheds were defined for these customers, and flow monitoring data were used to estimate average flows during the calibration periods as well as diurnal profiles. Future flows from these dischargers were assumed based on observed flows and the Pike Peak Area Council of Government’s (PPACG) Small Area Forecasts for population and employment if available.

2.1.2.6. Capacity Assessment The hydraulic model identified specific areas within the collection system where peak flows are projected to exceed the capacity of the existing pipes in the years 2000, 2015, 2025, or at buildout. The existence of a capacity deficiency does not necessarily imply that a sanitary sewer overflow (SSO) will result, only that hydraulic capacity criteria have been exceeded.

Significantly, the model indicated that the system has more than adequate capacity for current peak dry weather flows, and that no SSOs would result from the design storm, although some surcharging (i.e., water levels above the top of pipe, but below the ground) would be expected. This finding is consistent with the Springs Utility’s record of no SSOs attributable to lack of capacity. In the future, projected development would lead to increased surcharging and a higher risk of SSOs unless capacity improvements are made.

To provide capacity for increasing flows through 2025, 22 projects were defined, with a total estimated capital cost of $9.5 million. The projects were developed to the master planning level, and additional planning, pre-design, and design will be required to refine the projects. Each project was prioritized based on when capacity will be exceeded, and how high the water level is expected to rise (an indicator of the risk of an SSO). Implementation of these projects will allow the Springs Utilities system to continue to operate with a very low risk of capacity-related SSOs. However, it should be noted that SSOs can also be caused by pipe blockages, structural failures, washouts, or operational issues.

2.1.3. Level of Service Level of Service refers to the expected service provided to our customers. That is, our customers expect uninterrupted wastewater service from our collection system. While our goal is to have 100% uninterrupted service to our customers, there are many factors beyond our control (vandalism, improper sewage dumping, etc.) that make this very difficult.

The measurement utilized in measuring our goal of 100% is line stoppages. This refers to a mainline being blocked (or clogged) and overflowing into customers service lines. It should be noted that a customer’s service line can easily become blocked as well, however, these are not owned by nor the responsibility of the Utilities. As a result, these are not tracked with regards to the Level of Service.

Line stoppages can be attributed to four main causes. These are: grease, roots, other (rocks, debris, etc.), and unknown causes. With the current SSERP (see Section 2.2.1) and LCERP (see Section 2.2.2), these causes have been significantly reduced. While it is expected that this reduction will continue, we do not expect that our goal of 100% Level of Service will be attained due to the reasons beyond our control mentioned above. Figure 2-6 shows the number of stoppages per year from 1997 to October of 2008.


PAGE 2-13 DRAFT – Dec. 31, 2008

6561

63

39

32

53

30

43

2119

21

12

0

10

20

30

40

50

60

70

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Year

To

tal S

top

pa

ge

s

Figure 2-6 - Total Stoppages by Year

2.1.4. Potential Capital Improvements Specific sewer projects have been recommended for potential inclusion in Springs Utilities’ capital improvement program (CIP) based on the findings of the capacity analysis. Each project is documented with a general description, plan map, and planning-level capital cost estimate. (See Colorado Springs Utilities, Sewer System Capacity Evaluation, MWH, January 2006).

Each project was assigned an identifier based on the major basin in which it is located. The project identifier has the two or three letter designation for the major basin, followed by a sequential identification number. Figure 2-7 and Table 2-3 show the identified projects. As noted previously, the year when the capacity criterion is first exceeded does not correspond to the year in which the project must be completed. Some projects have very low priorities in terms of overflow risk and could be deferred, even though they exceed the capacity criteria in 2005. Many projects are driven by development, and the timing of construction depends on when the projected development actually occurs. Therefore, the list in Table 2-3 is a current snapshot of potential capacity issues that may need to be addressed in the future. In some cases, capacity issues identified in Table 2-3 may not be real due to further refinements that need to be made in the model setup.


PAGE 2-14 DRAFT – Dec. 31, 2008

Table 2-3 – Potential Capital Improvement Projects

Identi-fier

Year When Monitoring Capacity Begins

Location Estimated Capital Cost

(2006 Dollars)

PJ-1 2005 West of Monroe Place and Madison Street $114,763

USC-1 2005 North of Carefree Circle and west of Valencia Circle $170,688

CM-1 2005 Hidden Creek Drive and Broadmoor Valley Road to Star

$1,826,988

GOG-1 2005 North 31st Street near West Platte Avenue $59,400

SC-1 2005 Galley Road and Wynkoop Drive $91,375

C-1 2005 Taylor Street and Nevada Avenue $19,175

SC-2 2005 Audubon Drive and Airport Road $913,191

ST-1 2005 Terrace Drive and Mount Washington Avenue $108,180

TG-2 2005 Siferd Boulevard west of Hopeful Drive $766,594

USC-2 2005 Radiant Drive and Maizeland Road $1,060,359

USC-3 2005 Near Osgood Road and Wooten Road $180,263

PC-1 2015 * Chapel Hills Pump Station $546,875

LCC-2 2015 * North of Gambol Quail Drive $235,469

LCC-3 2015 * East of Vincent Drive and north of Willow Bend Circle

$1,176,484

UCC-1 2015 * Potomac Drive east of French Road $316,844

CV-1 2015 * South of Circle Drive and east of Janitell Road $131,538

GOG-2 2015 * South 21st Street near Cucharras Street $150,438

LSC-1 2015 * East of Granada Drive and Ember Drive $707,609

LSC-2 2015 * West of Astrozon Place and south of Hancock Expressway

$264,047

ST-2 2015 * Woodburn Street south of Saint Elmo Avenue $274,500

TG-1 2015 * West end of Crimson Circle North $105,750

LCC-1 2025 * North of Deliverance Drive and west of Union Boulevard

$234,375

Total $9,454,905

* Capacities of these pipes are dependent on future population growth rates which may change from the rates used in the 2005 version of the model


PAGE 2-15 DRAFT – Dec. 31, 2008

Figure 2-7 – Locations of Potential Improvement Projects


PAGE 2-16 DRAFT – Dec. 31, 2008

2.2. Wastewater Programs

Sanitary sewer systems are among the largest infrastructure investments that are made by communities. As such, it is imperative that they are managed, operated and maintained in a manner that maximizes their serviceable life. Springs Utilities is the largest single-operator sanitary sewer system in Colorado. In addition to preserving the value of public infrastructure, it is critical that sanitary sewer agencies minimize overflows from these systems. Overflows of domestic and industrial wastes can pose a substantial risk to public health and environment. Agencies throughout the nation vary widely in their success at achieving these objectives. National and State regulatory and enforcement attention toward SSOs has been increasing over the past several years.

In 2000, Springs Utilities began the Sanitary Sewer Evaluation Program (SSEP) as a means of assessing the condition of selected infrastructure components. The program was then expanded to include a comprehensive evaluation of sanitary sewer system condition and capacity. The Sanitary Sewer Evaluation and Rehabilitation Program (SSERP) was initiated in 2002 to further develop infrastructure assessment and to proactively address possible enforcement action from the Colorado Department of Public Health and Environment (CDHPE). The SSERP is focused on the evaluation and repair of pipe segments larger than eight inches in diameter, lift stations, and other critical infrastructure. In 2004, the Local Collectors Evaluation and Rehabilitation Program (LCERP) was instituted to assess and rehabilitate the majority of the collection system made up of pipe segments eight inches and smaller in diameter. With special attention required for sanitary sewer pipe segments that are installed in and near creeks, in 2005 Springs Utilities embarked on another comprehensive program named the Sanitary Sewer Creek Crossings Program (SSCC). Since the year 2000, Springs Utilities has spent over $100,000,000 on capital related work to improve its collection system.

Each of these programs was intended to provide a first pass condition evaluation and capital rehabilitation, repair and replacement of vulnerable collection system infrastructure. Since an ongoing monitoring, evaluation, and rehabilitation program is required to maintain the collection system, other programs were developed to address system needs into perpetuity, to include the Collection System Rehabilitation and Replacement Program and the Manhole Evaluation and Rehabilitation Program (MERP).

2.2.1. Sanitary Sewer Evaluation and Rehabilitation Program (SSERP) Springs Utilities embarked on the Sanitary Sewer Evaluation and Rehabilitation Program in January of 2002. This program was created to provide comprehensive and systematic evaluation of the sanitary sewer collection system and to complete the stipulations set forth in the CDHPE-regulated Compliance Order on Consent (COC). As the SSERP began to evolve, identification of system defects required the scope of the program to expand. As various locations and severity of defects were better understood, Springs Utilities expanded the program to ensure areas requiring repair be scheduled based upon system condition priority and budgeted on an annual basis. From its initiation in 2002 through 2007, over $63 million has been spent on this critical endeavor.


PAGE 2-17 DRAFT – Dec. 31, 2008

2.2.1.1. Program Development Two main regulatory drivers have guided the development of this program: the COC and the Federal Capacity, Management, Operations and Maintenance (CMOM) Rule.

2.2.1.1.1. Compliance Order on Consent (COC) On April 27, 2000, Environmental Protection Agency (EPA) headquarters issued its “Compliance Strategy for Combined Sewer Overflows and Sanitary Sewer Overflows”. The strategy directed the EPA Regional Office to submit to EPA Headquarters by July 28, 2000 an SSO Response Plan, which includes an inventory of SSO violations and how the top 20% of priority systems with SSO violations will be addressed each year. With this event, and the strong desire to address collection system deficiencies, Springs Utilities decided to take a proactive approach to enforcement action by volunteering to enter into a Compliance agreement with the CDHPE.

The COC, officially enacted in February of 2004, includes a schedule of compliance for Springs Utilities to conduct a comprehensive evaluation of its collection and transmission system and prepare schedules for facilities inspection, expansion, and repair. These evaluations and assessments are to be conducted in accordance with generally accepted practices.

The COC includes the following main components:

Transmission System. Springs Utilities or its consultant will evaluate the condition and capacity of its interceptors, trunk sewers and lift stations. This evaluation will include a review of existing information and supplementation with new information as necessary. Using this information, and any other available relevant data, Springs Utilities prepared and submitted Lift Station, Interceptor, and Trunk Line Condition Evaluation and Capacity Reports by due dates prescribed in the COC.

Collection System. Springs Utilities will evaluate the condition of its collectors. This evaluation will include a review of existing information and supplementation with new information as necessary. Using this information, and any other available relevant information, Springs Utilities shall prepare and submit a Collector Condition Evaluation Report. This final report is due in January of 2009.

System Deficiencies. Springs Utilities will use the results of its capacity evaluations and inspections as the basis for rectifying identified system deficiencies. Deficiencies found to pose an urgent threat of an overflow will be addressed immediately. Improvements to the remaining portions of the collection and transmission system will be scheduled in such a timeframe as to ensure no capacity or condition-related overflows occur.

2.2.1.1.2. Federal CMOM Rule The EPA worked several years with a broad-based advisory committee to formulate a Federal SSO policy. Although the EPA Administrator signed the resulting SSO Rule in January 2001, this regulation has not been officially enacted to date. The core of the proposed SSO Rule is a comprehensive capacity, management, operations and maintenance (CMOM) program designed to ensure that collection systems avoid SSOs. In January 2005 EPA issued the “Guide for Evaluating Capacity, Management, Operation, and Maintenance (CMOM) Programs at Saintary Sewer Collection Systems.” Assessing


PAGE 2-18 DRAFT – Dec. 31, 2008

current system capacity and identifying and prioritizing structural deficiencies are major components of this program. In addition to being a self-assessment and self-improvement tool for wastewater agencies, a well-documented CMOM program is expected to be a consideration in an affirmative defense against regulatory action which could be taken in the event of a major spill. Springs Utilities has incorporated its own CMOM program and actively works to self-assess and improve its system.

2.2.1.2. Purpose The purpose of the SSERP is to complete the following tasks based on milestone dates identified in the CDPHE-initiated COC:

Conduct a comprehensive evaluation of its collection and interceptor system,

Assess the capacity of the system to convey current and future average and projected peak flows,

Prioritize and perform correction of system deficiencies, and

Prepare and implement an enhanced sanitary sewer operation and maintenance manual and root control program.

To fulfill these objectives and to provide the framework and processes to include the evaluation and rehabilitation of the remainder of the collection system, the following specific requirements were developed:

Initiate, develop and implement a systematic approach to evaluating the condition of the collection system utilizing existing and updated databases and programs such as the Closed Circuit Television (CCTV), Oracle database, FIMS, RMS, WINCAN, and HydroWorks,

Assess the capacity of sanitary sewer pipelines that are larger than eight inches in diameter through the development of a hydraulic model to define and schedule required increases in system capacity,

Evaluate the condition and determine current and future capacity of lift stations,

Identify and prioritize rehabilitation, repair, and replacement projects for the sanitary sewer collection system,

Develop automated tools to track, identify and schedule rehabilitation, repair, and replacement projects,

Prepare design plans and specifications for rehabilitation, repair and replacement projects and oversee the implementation of actions taken,

Complete an enhanced operations and maintenance manual and root control program,

Implement refinements to grease management program,

Integrate and plan environmental, legal, planning, engineering, project management and operations functions and activities in support of the program and the COC.


PAGE 2-19 DRAFT – Dec. 31, 2008

Figure 2-8 – SSERP Work Management

2.2.1.3. Infrastructure Prioritization The original sanitary sewer evaluation concept prioritized large diameter sewers (typically interceptors and trunk lines) for several reasons. First, many of Springs Utilities’ large diameter pipelines had not been cleaned for some time. Springs Utilities historically relied on the industry guidelines that these types of pipeline are self-cleaning due to the comparatively high flows that they convey. As the sanitary sewer industry shifted away from this notion, Springs Utilities recognized the need for a large diameter sanitary sewer cleaning program. In 2000, Springs Utilities began the original Sanitary Sewer Evaluation Program (SSEP) for the primary purpose of evaluating the condition of large diameter sewers and developing a long-range maintenance program for them.

The COC included a schedule of compliance for Springs Utilities to conduct a comprehensive evaluation of its collection and transmission system and prepare schedules to inspect, rehabilitate, replace and repair collection system deficiencies. Within the SSERP, schedules for correcting system deficiencies are prepared immediately following system evaluation.

Interceptors and trunk lines remained the first priority under the proposed Compliance agreement and in the subsequent COC because (1) the work was already underway (approximately 20% were complete), (2) many of these pipelines are located close to waters of the State (commonly streams), and (3) the comparatively high flows conveyed by these pipelines can result in greater environmental impacts in the event of an overflow.

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Basin Prioritization

The prioritization by basin for interceptors, trunk lines and collectors is presented in Table 2-4. Several factors were considered during prioritization of sanitary sewer system components for evaluation. The primary considerations included:

Overflows and/or stoppages,

Known or suspected inflow and infiltration,

Current and/or future capacity,

Risk of erosion and/or washout,

Pipe and/or manhole deterioration,

Root, grease, or debris accumulations,

Component age,

Rodents,

Environmental permitting requirements, and

Easement encroachment (accessibility)

Table 2-4 - Basin Prioritization of Interceptors/Trunk Lines and Collectors

Basin Condition Evaluation Priority

Spring Creek 1

West Side 2

Shooks Run 3

Patty Jewett 4

South Tejon 5

Stratton Meadows 6

Downtown 7

Bear Creek 8

North Suburban 9

Lower Sand Creek 10

Mesa Valley 11

Bott 12

Templeton Gap 13

Cragmoor 14

Lower Cottonwood Creek 15

Upper Sand Creek 16


PAGE 2-21 DRAFT – Dec. 31, 2008

Basin Condition Evaluation Priority

Cheyenne Mountain 17

Pulpit Rock 18

Douglas Creek 19

Garden of the Gods 20

Popes Valley 21

Stratmoor 22

Rockrimmon 23

Pine Creek 24

Carson Valley 25

Upper Cottonwood 26

Peregrine 27

Briargate 28

Kettle Creek 29

2.2.1.4. Condition Assessments The National Association of Sewer Service Companies (NASSCO) Pipeline Assessment and Certification Program (PACP™) format are used to inspect and assess the condition of pipe segments. The pipe assessments have been conducted and prioritized using the PACP™ 1-5 ranking system along with a Springs Utilities A-E response code system as defined below:

5 – Immediate Attention: Defects requiring immediate attention (pipe has failed or will likely fail within the next five years),

4 – Poor: Severe defects that will become Grade 5 defects within the foreseeable future (pipe will probably fail in 5 to 10 years),

3 – Fair: Moderate defects that will continue to deteriorate (pipe may fail in 10 to 20 years),

2 – Good: Defects that have not begun to deteriorate (pipe unlikely to fail for at least 20 years), and

1 – Excellent: Minor defects (failure unlikely in the foreseeable future.)


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Table 2-5 – Colorado Springs Utilities Response Coding System

Response Code

Structural Defects O&M Defects

A – Requires immediate attention

Minimize the risk of a sanitary sewer overflow by implementing mitigating measures immediately (e.g., bypass pumping, temporary repair, obstruction removal)

If the mitigating measure is temporary: Initiate planning or design of long-term corrective measures (e.g., permanent repair, infrastructure replacement, or rehabilitation), within a time frame commensurate with the expected longevity and reliability of the mitigation effort.

Minimize the risk of a sanitary sewer overflow by performing required maintenance (e.g., cleaning) immediately upon defect confirmation, and

Schedule and perform enhanced maintenance, as appropriate.

B – Requires near term repairs or maintenance in 90 to 180 days

Minimize the risk of a sanitary sewer overflow implementing mitigating measures within 90-180 days of defect confirmation, (e.g., bypass pumping, temporary repair, obstruction removal)

If the mitigating measure is temporary: Initiate planning or design of long-term corrective measures (e.g., permanent repair, infrastructure replacement, or rehabilitation), within a time frame commensurate with the expected longevity and reliability of the mitigation effort.

Minimize the risk of a sanitary sewer overflow by performing required maintenance (e.g., cleaning) within 90-180 days of defect confirmation, and


C – Requires repairs or maintenance to be completed within 1-2 years

Commence planning for long-term corrective measures (e.g., repair, replacement, or rehabilitation), and

Perform design, permitting, and construction, as appropriate, of long-term corrective measures within 1-2 years of inspection data analysis.

Commence planning for required maintenance (e.g., cleaning),

Perform maintenance within 1-2 years of inspection data analysis, and


D – Re-inspect within 3-5 years

Perform a re-inspection within 3-5 years of inspection data analysis.

E – Re-inspect and maintain through normal O&M

Perform a re-inspection during routine inspection of the basin, sub-basin, or other defined area, typically within 15 years of the initial inspection.

Perform maintenance consistent with the schedules contained within the Colorado Springs Utilities Sanitary Sewer Operations and Maintenance Manual.


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2.2.1.5. Progress The SSERP has consistently met all deadlines related to the COC. The following table illustrates the significant progress of critical work tasks in the program from inception through 2007:

Table 2-6 - Progress of Critical SSERP Tasks

Task Miles

CCTV inspection footage (First Pass) 185.5

Cured-in-Place pipe installed 51.5

Replacements: 0.86

The following graph shows the relative decrease of releases over time:

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Figure 2-9 – Trend Analysis of Releases through Time


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2.2.1.6. Schedule The SSERP COC schedule extends through 2012; however if the number of defects found per pipe segment and allocated budget remains at current levels, capital work resulting from first pass inspections are scheduled for completion by the end of 2010. The final comprehensive report, the Collectors Condition Assessment, is due to the State in January of 2009, but is currently being prepared and is expected to be submitted early. All other major dates have been met with re-inspections and capital work resulting from re-inspections continuing into perpetuity.

2.2.1.7. Budget Capital expenditures in the SSERP since its inception through 2007 are listed in Table 2-7:

Table 2-7 – SSERP Capital Expenditures

2002 2003 2004 2005 2006 2007 Total

$3,177,826 $6,651,164 $10,320,915 $15,440,532 $18,564,097 $9,747,149 $63,901,683

Projected capital expenditures resulting from first pass inspections are listed in Table 2-8. The first pass of the program is expected to be completed in 2010. After this a long term maintenance program will ensure that assessments and maintenance work are carried out.

Table 2-8 – SSERP Capital Projections

2008 2009 2010 Projected Total

$6,444,074 $3,326,704 $415,000 $74,087,461

2.2.2. Local Collectors Evaluation and Rehabilitation Program (LCERP)

2.2.2.1. Purpose Initiated in 2004, the primary objective of the Local Collectors Evaluation and Rehabilitation (LCERP) initiative was to reduce SSOs through a systematic inspection, rehabilitation, replacement and monitoring program for pipes smaller than ten inches in diameter. The full development of this program will also fulfill anticipated requirements of the forthcoming federal CMOM regulations. The LCERP was modeled after the SSERP and included the following objectives:

o Develop and integrate a workflow process to schedule CCTV, cleaning, planning, engineering and construction activities,

o Develop a systematic approach, leveraging tools created for the SSERP, to evaluate the condition of existing pipes and manholes to include ArcFM, Maximo, WINCAN, InfoWorks and required system linkages,


PAGE 2-25 DRAFT – Dec. 31, 2008

o Continuation of the capacity analysis of the sanitary sewer system through enhancements to the hydraulic model, developed through the SSERP,

o Identify, prioritize and complete required rehabilitation, repair and replacement projects,

o Develop, through the workflow process, IT solutions to track and schedule repair, replacement and rehabilitation projects,

o Develop a system that could eventually be internalized and become part of the regular Operation and Maintenance of the system.

2.2.2.2. Program Development The LCERP was developed as a 20-year program with a 60-mile per year CCTV inspection schedule. The CCTV inspection process utilizes the NASSCO PACP coding and classification system and mirrors the SSERP’s action schedule for system deficiencies. The LCERP is truly a collaborative effort with the following Springs Utilities departments working together toward a common goal:

- Construction and Maintenance - Wastewater Pipeline Operations - Planning, Engineering and Resource Management - Environmental Services - Program Management - Information Technology Services

More than 50 Springs Utilities personnel contribute on a daily basis to these programs and IT systems have been developed to aid in work identification, scheduling, and compliance monitoring. Enterprise systems and custom software applications are now integrated to the extent that pipe cleaning, CCTV inspections and video, engineering assessments, rehabilitation work order generation, and status reporting all work together in a microcosm of an enterprise based asset management system.

2.2.2.3. Basin Prioritization and Schedule One major goal of each program was to determine an optimal basin priority schedule. The first approach considered was to perform CCTV inspections on the entire system as a first step, then to evaluate and prioritize required work on all pipes. Although this approach would be holistic, it would require the rehabilitation of critical pipe segments to be postponed until the entire system was evaluated. Instead, the team decided to determine which basins had the most need for evaluation and repair. The approach chosen combined historical data from the basins, organizational knowledge and engineering evaluation and established a schedule with the most problematic basins being inspected, evaluated and rehabilitated first. As the programs develop, the basin schedule is continually updated based on system statistics such as occurrences of SSOs, problem holes, and emergency call-outs. The current basin priority schedule for CCTV inspection is as follows. To date, the top five basins have been inspected, and the top four have been evaluated. Repair and rehabilitation schedules have been set based on individual pipe condition (as described above).


PAGE 2-26 DRAFT – Dec. 31, 2008

Table 2-9 – Basin Schedule

Basin Name Target Start Target Finish

Shooks Run 06/07/2005 04/14/2005

Patty Jewett 09/02/2006 08/10/2006

West Side 02/05/2007 02/01/2007

Spring Creek 04/09/2008 05/25/2008

Stratton Meadows 07/26/2008 09/04/2008

South Tejon 04/04/2009 04/12/2009

Garden of the Gods 12/17/2009 11/28/2009

Templeton Gap 03/09/2011 04/11/2011

Upper Sand Creek 09/14/2012 08/04/2012

Downtown 12/07/2012 10/14/2012

Cragmoor 04/16/2013 02/05/2013

Lower Sand Creek 06/27/2014 03/29/2014

Mesa Valley 10/20/2014 07/07/2014

North Suburban 01/31/2015 10/02/2014

Bott 04/26/2015 12/20/2014

Rockrimmon 01/23/2016 08/14/2015

Popes Valley 03/14/2016 10/07/2015

Bear Creek 06/23/2016 01/10/2016

Douglas Creek 03/18/2017 10/17/2016

Lower Cottonwood Creek 02/16/2018 09/18/2017

Carson Valley 10/30/2018 05/28/2018

Cheyenne Mountain 03/01/2019 10/09/2018

Peregrine 05/26/2019 01/10/2019

Pulpit Rock 07/06/2019 02/23/2019

Pine Creek 08/06/2019 03/28/2019

Briargate 03/16/2020 12/01/2019

Kettle Creek 03/28/2020 12/14/2019

Upper Cottonwood Creek 07/24/2020 04/03/2020

Stratmoor 07/26/2020 04/05/2020

2.2.2.4. Evaluation Methodology The NASSCO PACP methodology allows internal pipeline inspection crews, whether in-house or contracted to provide similar data formats for evaluation by engineers, providing a reliable snapshot of the existing condition for evaluation and yielding consistent results


PAGE 2-27 DRAFT – Dec. 31, 2008

when applied by multiple crews. Information collected also provided baseline data to be used for future inspections, asset degradation monitoring and system base lining.

2.2.2.5. Improvement Planning As discussed previously, since the NASSCO rankings do not specify a response time Springs Utilities created a two response schedule, one for Structural issues and one for Operational issues. The rankings range from an “A” which is defined as “requiring immediate attention” to an “E” which falls into a normal maintenance schedule. Pipe segments assigned a critical categorical ranking “A” must be stabilized and/or repaired within 36 hours. The next level of critical pipeline structural or Operations and Maintenance ratings require work within six months, then two years, then re-inspected within five years, and finally to be re-inspected in fifteen years. Due to the aggressive schedule for completion of the work, the planning team continually redefines its planning matrix for identifying project constraints that could cause delays to the making system repairs. Some of these delays included permitting requirements, property access, and contractor availability. The Springs Utilities team assigns internal specialists to each of these potential delays; environmental specialists develop a permits acquisition plan and coordinate all permits directly with regulatory agencies, real estate services teams assist in alleviating right of entry and access for construction, while the project management team bid task order contracts to secure contractors for each project.

2.2.2.6. Rehabilitation Methods When determining how to systematically rehabilitate its collection system in the most cost effective manner, Springs Utilities considered several rehabilitation methods, including trenchless technology. Because of its success with Cured-in-Place Pipe (CIPP) and since CIPP installation is approximately 67% less costly than traditional open cut replacement, Springs Utilities decided that CIPP would be the preferred rehabilitation method. Although CIPP installation is not recommended for every deficient pipe segment, such as pipes experiencing sags, holes, and lack of capacity, it can be used in situations where open cut replacement is preferred in a structural sense but is too costly to complete. Examples of these situations include pipes that are buried too deep for safe trenching, pipes located under permanent structures, and pipes buried beneath fresh pavement or mature, expensive landscaping.

2.2.2.7. Progress

Table 2-9 illustrates the significant progress made in the LCERP since its inception in 2005 through 2007:

Table 2-10 – Progress of LCERP Tasks

Task Miles

CCTV inspection footage (First Pass) 325.9

Cured-in-Place pipe installed 47.7

Replacements: 7.21


PAGE 2-28 DRAFT – Dec. 31, 2008

Since the inception of the SSERP and LCERP, collection system stoppages have significantly decreased as shown in Figure 2-10:

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2.2.2.8. Budget Table 2-11 contains historical capital expenditures on sewer pipes with diameters eight inches and smaller. Over twenty-three million dollars was spent on this program from 2004 to 2007.

Table 2-11 – LCERP Capital Expenditures

2004 2005 2006 2007 2008 Total

$486,208 $1,930,806 $9,905,847 $11,015,580 $7,160,743 $30,499,184

Projected capital expenditures resulting from first pass inspections are as follows:

Table 2-12 – LCERP 10-Year Capital Projections (in millions)

2009 2010 2011 2012 2013 2014 2015 2016 2017 2018

$7.38 $8.54 $10.3 $10.1 $9.47 $9.19 $8.97 $9.35 $6.70 $7.92


PAGE 2-29 DRAFT – Dec. 31, 2008

2.2.3. Sanitary Sewer Creek Crossings Program (SSCC)

2.2.3.1. Background Although the sanitary sewer pipelines in and near creeks were being evaluated as part of either the SSERP or LCERP, in July of 2005, the commitment was made that the first set of these crossings in the major creek basins (131 pipe segments in total) would be both inspected and stabilized in less than 12 months. When Amendment One of the existing COC was finalized in December of 2005, the deadline inspecting and stabilizing all 131 major creek crossings was January 31, 2006 and June 30, 3006, respectively. The next deadlines stipulated in Amendment One entailed inspecting and stabilizing all sanitary sewer pipelines that cross minor drainages in Springs Utilities’ service territory (238 pipe segments in total) by June 30, 2006 and December 31, 2006, respectively. This new initiative considerably expedited the inspection, evaluation and rehabilitation of these rather unique grouping of pipelines and presented unexpected and significant challenges.

Although not included in Amendment One of the COC, it was determined early in the program that pipes located in close proximity to water ways and paralleling them should be given the same level of attention as crossings since they presented the same level of risk. This subset of sanitary sewer pipe segments are those located within 50 feet of the banks of the major and minor drainages and were named “longitudinals”. After considerable data gathering and ground truthing, this subset totaled over 1600 pipe segments.

Many challenges faced the team during the initiation of the SSCC. These challenges included quantification, inspection methodology, evaluation and prioritization processes, and the execution of the required improvements in an extremely constrained timeframe.

2.2.3.2. Regulatory Context Because of SSOs reported during the period between January 14, 2004 and November 16, 2005 and to resolve alleged violations of the Colorado Water Quality Control Act (CWQCA) and Federal Clean Water Act (CWA), Colorado Springs Utilities executed Amendment Number One of the COC on December 29, 2005. This new amendment contained compliance dates that expedited the evaluation and rehabilitation/repair of the sanitary sewer pipelines that cross major and minor drainages in Utilities’ service area.

As part of the amended order, required actions regarding the sanitary sewer stream crossings were divided into two phases. The scope of work for Phase I includes the 131 pipe segments crossing Cottonwood, Fountain, Monument, Sand, and Shooks Run Creeks. The due dates to complete the assessment of these pipelines and to implement mitigating measures for those rated a “5” (in critical condition) were January 31, 2006 and June 30, 2006, respectively. The Utilities met these deadlines.

The COC further stipulated that Springs Utilities determine the condition of the remaining 238 wastewater stream crossings within Springs Utilities’ service area no later than June 30, 2006 and implement mitigating measures no later than December 31, 2006. Springs Utilities met these deadlines.

2.2.3.3. Quantification The first major challenge for Springs Utilities was to quantify the number of wastewater pipelines that actually cross drainages in its service area. Review of existing GIS data,


PAGE 2-30 DRAFT – Dec. 31, 2008

recent fly-over imagery, and extensive ground-truthing yielded a list of 369 pipe segments, with 131 pipe segments crossing the five major creeks and 238 pipe segments crossing minor drainages. Although not part of the initial creek crossings project, ongoing inspection data reveals approximately 1,600 pipelines that parallel the creeks and are within 50 feet of the creek banks.

2.2.3.4. Inspection Methodology While national standards exist for internal condition assessments, the lack of industry standards for external inspections on creek crossings presented the project team with the challenge of developing its own methodology. Thus, a standard was developed for inspections based on its ability to (1) provide a reliable snapshot of the existing condition for evaluation and (2) yield consistent results when applied by multiple crews. Information collected also provided baseline data to be used for future inspections, asset degradation monitoring and system base lining. Standardized inspection techniques for both internal and external inspections were developed. For internal condition assessments, Springs Utilities utilized the NASSCO PACP formats. External pipe inspection forms were developed to record in-situ conditions of the pipeline and streambed, stream bank along with other site constraints.

2.2.3.5. Evaluation and Prioritization In addition to consistency in evaluations, Springs Utilities established data storage systems to allow for historical asset tracking. These systems provide Springs Utilities with the capability to compare future assessments to this baseline to develop risk based assessments and track asset degradation. These standard procedures were documented in the Springs Utilities Quality by Design (QBD) document control process. Using these standard criteria, condition assessment categorical rankings (1-5 scale, 5 being the worst condition) for internal and external asset condition were combined and used to prioritize system improvements or future monitoring.

2.2.3.6. Execution Challenges Execution challenges have occurred in three main areas: permitting, terrain impacts, and local economic trends.

Permitting: With the project locations’ close proximity to drainage ways, permits can be required from the U.S. Army Corps of Engineers (USACOE), the Federal Emergency Management Agency (FEMA), and the Colorado Division of Wildlife (CDOW), among others. Each of these permits have the potential to take six to 18 months to acquire and most times require a 60% engineering design and detailed analysis to begin the process. With the long lead time and the need to avoid construction in the creeks during high flow periods, the permitting requirement necessitates an aggressive and holistic approach to all projects.

Terrain impacts: The city’s topography is highly varied ranging from lesser foothills and valleys to rolling plains, making waterways abundant in the Springs Utilities’ service territory. These waterways also presented the “path of least resistance” for thousands of feet of sanitary sewer pipelines installed from the early twentieth century until recent times. In addition, Colorado Springs’ meteorological classification is alpine desert with 15 to 16


PAGE 2-31 DRAFT – Dec. 31, 2008

inches of precipitation per year. Much of the precipitation falls voluminously from powerful spring storms that have potentially damaging effects on infrastructure.

Creeks in Springs Utilities’ service area, especially those with banks primarily made of sand, can move up to 10 feet vertically and 40 feet horizontally in one storm event. Infrastructure that was once 30 feet away from a drainage channel can be left in the middle of an active creek after one heavy storm. This environment makes pipes in or near creeks extremely difficult to monitor, stabilize and repair, especially with longevity as a goal.

Local Economic Trends: Considering local economic trends is crucial to effectively planning a project since the market can greatly affect the three components of project management: scope, budget and schedule. Trends that currently affect or will likely affect the completion of the Sanitary Sewer Stream Crossings project include qualified resource availability, escalating material costs, and community growth.

By expediting the assessment and repair of stream crossings in addition to the substantial scope of the SSERP and LCERP projects, the amount of work that the project team, including outside contractors and regulatory agency personnel, needs to accomplish in a condensed timeframe is straining qualified human resources. From practiced engineers handling project analysis and design, to contractors and in-house personnel competent in closed-caption television or trenchless pipeline rehabilitation, to experienced plan reviewers in governing agencies, this project has added a considerable amount of work to all stakeholders. This increased workload comes at a time when the local demand for qualified individuals is escalating, resulting in a higher job turnover rate, longer turnaround times for all tasks, and less knowledgeable and experienced people doing the work.

A second economic trend that has the potential to greatly affect the sanitary sewer stream crossing work is material availability. The completion of the creek crossings project requires considerable amounts of materials to include concrete, rip-rap, and steel. Each of these supply markets have been variable, resulting in shortages and sky rocketing costs. The project team must keep close watch of this trend to ensure that materials are available to complete the projects and the budget allocations are able to accommodate escalating costs.

Thirdly, because of local community growth and urban expansion, increased storm run-off results in significant changes to drainages in Springs Utilities’ service area. Dynamic erosion, sedimentation, and creek bed expansion conditions in local drainages continually affect the total number of crossings and the stability of each pipeline. Because the scope of the project is in a constant state of flux, budget and schedule parameters are also volatile, requiring a flexible and continually evolving project management approach.

2.2.3.7. Continuous Improvements Continuous improvement opportunities include post-storm inspections and elimination of creek crossings.

Post- Storm Inspections: As part of Springs Utilities’ continued commitment to addressing vulnerable creek crossings, a Post-Storm inspection process was developed with Operations, Engineering, IT and Project Management personnel. Triggered by storm events and water levels in the creeks, up to 10 teams of two Operations personnel visit and inspect all crossings on impacted routes. When the pipeline becomes vulnerable due


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to instability in the creeks, debris, degradation, erosion or flow undermining the infrastructure, Operations personnel immediately work to stabilize the crossing through temporary hardening. Qualified engineers are then notified, and perform a comprehensive inspection of the vulnerable crossings. They then recommend a stabilization response and a timeframe to perform the work. The work is then routed to project management for execution.

Each step of this process is automated and implemented by the IT department. By utilizing carefully developed and agreed upon project requirements, incorporating U.S. Geologic Survey (USGS) gauging information and combining technology with field constraints, programs were created to implement a fully automated inspection process. Ruggedized laptops were equipped with baseline inspection information, data gathering tools, and automation that enables current information to be downloaded into existing databases.

Elimination of Creek Crossings: Because of the expensive yet short-term repairs that creek crossings require, Springs Utilities continually evaluates crossings for the possibility of rerouting or eliminating them. To date, ten pipe segments have been removed from the creek environment with twelve additional segments planned for elimination by mid-2009. Preliminary findings indicate that up to 10% of all creek crossings have the potential to be eliminated, with the potential to substantially decrease capital and O&M costs during the program’s duration.

2.2.3.8. Budget and Schedule With continual monitoring of the creek crossings, maintenance activities are ongoing to address scouring and erosion and replace hardening materials such as rip-rap. Because of the dynamic nature of creeks, hardening and longer term projects continue to be planned, designed, permitted, and executed. From its inception through 2007, approximately $15 million was expended on pipes in or near creeks. The pipes in creeks effort is projected to cost upwards of $40 million by the time all of the crossings are addressed during the first pass of this program (through 2012) with capital expenditures from 2013 through 2017 adding another $20 million to that estimate. Operation and maintenance costs are projected to be at least $1 million per year continuing into the foreseeable future.

2.2.4. Other Programs The three Wastewater Programs discussed above (SSERP, LCERP and SSCC) were created to address the first pass inspection and rehabilitation of the collection system, to include critical infrastructure such as manholes. For funding and logistical reasons, project team members decided that manholes should be separated into their own endeavor since they are common to all three wastewater programs. The Manhole Evaluation and Rehabilitation Program (MERP) is proposed to begin in 2009 and is estimated to be a 20-year first pass through program.

Since collection system re-inspections, evaluations, rehabilitations and repair will continue into perpetuity, other programs have been initiated to address capital expenditures on the programs after the first pass tasks and COC stipulations are met. The first of these programs is the Collection System Rehabilitation and Replacement Program, which began


PAGE 2-33 DRAFT – Dec. 31, 2008

in 2008, and was budgeted to address capital work resulting from SSERP re-inspections. The second is the SSCC Rehabilitation and Replacement Program, projected to begin in 2013, and initiated to rehabilitate and replace pipes in or near creeks that will be re-inspected after the COC is completed.

2.3. Fats, Oil and Grease Evaluation

Fats, Oil and Grease (FOG) are generated during food preparation, equipment maintenance, and food-service sanitizing processes. Many foods that are processed and served contain FOG, including; meats, sauces, gravy, dressings, deep fried foods, baked goods, cheeses, butter, milk and others. The discharge of FOG to sanitary sewer systems is a problem as FOG cools, it congeals, and can accumulate in the sewer and cause a backup or overflow. This can result in significant hazards to public health, and hazards to the food service establishment, damage to other establishments and residences, or damage to the public sewer system. FOG sources include commercial, industrial and residential activities in the Springs Utilities collection system. Figure 2-11 shows camera images of a sewer pipe that has heavy grease deposits that have accumulated in it and a pipe that is clean with no grease deposits.

Figure 2-11 – TV Camera of Pipe with Grease vs. Pipe with no Grease

Springs Utilities has an active FOG reduction program in place and consistently seeks to reduce FOG inputs to the collection system. As seen in the Figures 2-1 and 2-2 above, total stoppages and stoppages caused by grease have decreased markedly over the past 10 years. Despite this fact, there are still substantial amounts of FOG encountered at the headworks of the wastewater treatment facilities.

Commercial and industrial sources of FOG include food service establishments, centralized waste treatment entities, food and beverage production facilities, and other smaller generators. Changes to the Springs Utilities line extension standards over the years have helped implement FOG reduction capabilities through the use of grease interceptors, grease traps and best management practices (BMPs). However, if


PAGE 2-34 DRAFT – Dec. 31, 2008

commercial and industrial sources do not properly maintain interceptors/traps, or are lax in their implementation of BMPs, the potential for FOG related problems increases.

While Springs Utilities cannot actively regulate residential sources of FOG, we have established many public education elements to help residential customers understand the importance of controlling FOG discharges to the sewer. These include bill-stuffers, fliers, targeted mailings, website information, and FOG prevention campaigns (such as during FOG intensive holiday periods). Other residential FOG sources can include home-based cooking operations at a commercial level.

Efforts are being directed toward recycling fryer oils and brown grease in the collection system for use as feed stock in biodiesel and/or methane production. While these opportunities are in their infancy, several projects are underway to determine potential renewable sources of energy from these waste products.

WASTEWATER INTEGRATED MASTERPLAN WASTEWATER TREATMENT FACILITIES MASTERPLAN


3. WASTEWATER TREATMENT FACILITIES MASTERPLAN

Colorado Springs Utilities owns and operates two wastewater treatment plants. The northern area of Colorado Springs is served by the J.D. Phillips Water Reclamation Facility (JDPWRF). The rest of the city is served by the Las Vegas Street Wastewater Treatment Facility (LVSWWTF).

3.1. Las Vegas Street Wastewater Treatment Facility

3.1.1. Description The Las Vegas Street Wastewater Treatment Facility (LVSWWTF) has two parallel secondary treatment processes consisting of an Advanced Wastewater Treatment (AWT) Activated Sludge Process and the trickling filter solids contact (TF/SC) process, referred to as the Bioplant. Currently, the total permitted capacity of LVSWWTF varies seasonally from 65 million gallons per day (mgd) during January and February to 75 mgd over the remaining year.

At the present time, all flow into LVSWWTF is treated by the AWT process. The Bioplant has not been in service since 1998. The AWT process has adequate capacity to treat the current influent flow. The AWT process provides a higher quality effluent because of greater efficiency in ammonia and solids removal.

3.1.2. Capacity Evaluation

3.1.2.1. Current Permitted Capacity The permitted capacity of the LVSWWTF is defined by two different parameters. The first parameter is flow rate (gallons treated/day). The second parameter describes the strength of the wastewater in terms of organic loading (pounds of CBOD/day – defined below).

3.1.2.1.1. Flow Capacity The LVSWWTF’s permitted flow capacity is 75 mgd from March through December and 65 mgd January through February. The permitted 65 mgd capacity is comprised of 47 mgd capacity in the AWT and 18 mgd in the parallel Bioplant. For the remaining portion of the year outside of January and February, capacity consists of 18 mgd in the Bioplant and 57 mgd in the AWT totaling 75 mgd. These capacities are shown in Table 3-1.

Table 3-1 – Permitted Flow Capacity of LVSWWTF

Permitted Capacity (mgd) Season AWT Bioplant Total

January through February 47 18 65

March through December 57 18 75



The Bioplant process is mainly a fixed film system while the AWT is a suspended growth system. Since the two systems retain different amounts of biomass per unit volume, the wastewater temperature has a greater affect on the AWT process. Thus, the AWT is significantly affected by ambient temperature and thus has a lower permitted capacity during the cold weather months, whereas the Bioplant is unaffected and its capacity remains constant.

3.1.2.1.2. Organic Capacity The plant’s organic loading rate is defined by pounds of carbonaceous biochemical oxygen demand (CBOD) per day. The CBOD test measures the organic content of wastewater. Over a five-day period, the oxygen used by microorganisms in the biochemical oxidation of organic matter is measured. This result indicates the strength of the wastewater.

The total permitted organic capacity of LVSWWTF is 238,000 pounds CBOD/day (30-day average) throughout the year. However, there is month to month variation in the permitted organic capacity between the AWT and Bioplant. The permitted capacities are presented in Table 3-2.

Table 3-2 – Permitted Organic Capacity of LVSWWTF

Permitted CBOD Capacity (mg/L – 30 Day Average)

Month

AWT Bioplant Total

January 168,431 69,569 238,000

February 168,431 69,569 238,000

March 177,707 60,293 238,000

April 177,707 60,293 238,000

May 177,707 60,293 238,000

June 177,707 60,293 238,000

July 177,707 60,293 238,000

August 184,053 53,947 238,000

September 177,707 60,293 238,000

October 177,707 60,293 238,000

November 177,707 60,293 238,000

December 177,707 60,293 238,000

Historical yearly averages for CBOD loading at LVSWWTF are presented in Figure 3-1. The data has trended up and down over the period analyzed. There appears to be a similar trend between CBOD loading and influent flow on an annual basis. However, it will be shown that flow is not related to CBOD loading on a daily basis. Since 2005, there has been a downward trend in the organic loading rate at the plant. On an annual average basis, the organic loading at the AWT is well below the permitted capacity.



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Figure 3-1 – Historical Annual Averages for CBOD Data for the LVSWWTF

From a monitoring perspective, it is interesting to know if the organic loading (the strength of the wastewater) has seasonal trends. Figure 3-2 plots the monthly average CBOD loading at LVSWWTF from 2000 to 2007. The plot shows that there are no consistent seasonal patterns to organic loading. Sometimes the cold weather months have higher strength wastewater, but other years there are spikes in the spring or summer time loading. No consistent seasonal patterns are apparent. In addition, correlation between monthly average flows and CBOD loading is not apparent.



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Figure 3-2 – Historical Monthly Averages for CBOD5 Data for LVSWWTF

It is also interesting to look at the relationship between influent flow and organic loading on a daily basis. In 2000, Brown and Caldwell analyzed some of the LVSWWTF operations as part of an application for site modification that was submitted to the State. In their analysis they graphed influent flow against organic loading for data from 1997 to 2000. They noted in their analysis that there was no relationship between influent flow and the magnitude of organic loading.1

In Figure 3-3 below, influent flows have been plotted against organic loading data from 2000 to 2007. If flow is related to organic loading, we would expect to see some type of relationship between the two variables – for example at low flow, the influent CBOD might be high, and at high flow the influent CBOD might be low. If this were the case, the data would not be widely scattered, and would plot along a line. However, inspection of the data in Figure 3-3 shows that the same influent CBOD loading occurs over most of the flow range. Also, at a given flow, the influent CBOD value varies over a wide range. The R2 term shown on the plot gives an idea of the scatter. As R2 approaches zero, the data is very widely scattered and the two variables plotted are not related. As the R2 term approaches 1, the data is explained very well by a line passing through the data, and the two variables are related. Because the R2 term in Figure 3-3 is 0.01, this indicates that the

1 Brown and Caldwell, Las Vegas Street WWTF Application for Site Approval for Modification or Expansion of an Existing WWTP, Technical Memorandum, Nov. 27, 2000, p. 2.



data is widely scattered, and means that there is no relationship between influent flow and the strength of the wastewater coming into the plant.

Plot of CBOD vs Flow (2000-2007 data with outliers removed)

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Figure 3-3 – Comparison of Influent Flow and Organic Loading for LVSWWTF

In summary, the CBOD data indicates that organic loading at the LVSWWTF is well below the permitted capacity. The annual average organic loading rate at the plant has decreased over the past few years. The data also has shown that there is no relationship between organic loading and the influent flow rate on a day to day basis.

3.1.2.2. Future Capacity Requirements Analysis Planning for future capacity at LVSWWTF requires an understanding of the impact of new 2011 permit limits, population projections, and future development requirements.

3.1.2.2.1. Permit Limits and Capacity New permit effluent limits will take effect in 2011. Analysis of the expected effluent limits has been completed. However, assumptions had to be made in the analysis. These assumptions will be reviewed by the CDPHE when the permit is renewed. The CDPHE may take a different approach than what Springs Utilities proposes.

It appears the plant can comply with the lower ammonia limits as projected by the preliminary analysis. However, if the CPDHE takes a different approach than Springs Utilities in determining the new ammonia limits, the situation could change. If the CDPHE issues significantly lower ammonia limits, then under a compliance schedule, plant modifications may become necessary.



The permit renewal in 2011 is also expected to contain new disinfection requirements. The current permit uses fecal coliforms as the indicator organism to demonstrate compliance. The 2011 permit is expected to require E. coli to be the indicator organism. The E. coli limits will be lower than the previous fecal coliform limits.

3.1.2.2.2. Historical Population and Influent Flow

Before assessing future capacity needs, it helps to see historical flows and population relationships. Table 3-3 presents flow and population data from 1990 to 2007. Annual rainfall rates are included in Table 3-3 and are discussed later in this section.

Table 3-3 – Historical Influent Flow, Population Data and Rainfall Data for LVSWWTF

Year Flow (mgd) Population Rainfall (in/year)

1990 33.3 281140 19.1

1991 33.8 290733 17.5

1992 35.6 298755 14.8

1993 36.4 307126 13.4

1994 39.2 315590 20.8

1995 44.4 325000 22.1

1996 43.8 323185 16.6

1997 46.6 332611 23.1

1998 45.5 342037 16.2

1999 46.8 351463 27.6

2000 45.5 360890 16.9

2001 44.6 369853 15.0

2002 42.1 373328 7.8

2003 42.4 377006 12.4

2004 44.6 380073 21.1

2005 42.3 384876 11.9

2006 42.3 391449 13.8

2007 42.2 402417 11.8

Figure 3-4 below plots historical flows and population data from Table 3-3. Several trends are apparent in the data. First, from 1990 to 1997 there was growth in population and influent flows. But from 1997 onward, the flow peaked in 1999 and then had a downward trend through 2007. The magnitude of the downward trend is surprising given that population increases still occurred during the time period from 1998 to 2007. Several factors have contributed to the downward trend in flow: rainfall rates, collection system improvements, and water conservation efforts.



Population vs. Influent Flow for Las Vegas Street Wastewater Treatment Facility

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Figure 3-4 – Historical Population and Influent Flow Data for LVSWWTF

Rainfall rates: The 30-year average annual precipitation rate for Colorado Springs is 17.43 inches (National Weather Service). Figure 3-5 plots the 30 year annual rainfall average (green line), annual rainfall rates (magenta lines) and influent flows at LVSWWTF (blue lines). Prior to 1993 flow is not correlated with rainfall. But after 1993, increases and decreases in rainfall appear to influence influent flow at the plant. One factor in the decrease of influent flow at the plant over the past 10 years is the fact that annual rainfall for six of the past seven years has been below the 30-year average and includes the drought of 2002.

Collection system rehabilitation: Rehabilitation efforts have been significant from 2003 to 2008. Slip lining of large diameter main lines and more recently smaller diameter collector lines has reduced infiltration. Figure 3-6 plots cumulative miles of collection mains (through 2007) that have been slip-lined with a cast-in-place liner. The reduction of infiltration of groundwater flow due to the lining of collection lines is difficult to quantify. This is partly due to the fact that collection mains with high infiltration flow rates were slip-lined first. Several years of above average rainfall will be needed to provide a more accurate picture of how the rehabilitation efforts have reduced infiltration. One preliminary indicator can be seen in the data from 2005 to 2007 on Figure 3-5. The annual rainfall rate was higher in 2006 than either of 2005 and 2007. But the annual average influent flow rate at LVSWWTF did not exhibit a response to the slightly higher rainfall rate in 2006 (as it has



with other increases in annual rainfall). It will be interesting to see what happens to influent flow when above average rainfall occurs several years in a row.

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Figure 3-6 – Cumulative Miles of Lined Pipes vs. Flow and Rainfall for LVSWWTF



Water conservation: Water conservation efforts over the past six to seven years have encouraged lower water use. Indoor water use reductions can be estimated through rebate programs that Springs Utilities has promoted and managed. Table 3-4 lists the estimated water savings that occurred during 2007 as a result of water conservation programs that allow water savings to be reliably calculated. The number of units in service is the accumulated totals of rebates that have been offered to the public since 2002. The wastewater reductions calculated from the rebate programs can be reliably quantified.

Table 3-4 – Estimated Wastewater Reductions through Conservation

Type of Program No. of Units in Service Through 2007

Water Savings (mgd)

Ultra Low Flush Toilets Rebates 3,205 0.068

Residential High Efficiency Toilet Rebate 55 0.002

Residential Clothes Washer Rebates 12,009 0.148

Showerhead Fixture Rebate/Promotions 34,763 0.166

Faucet Aerator Promotions 20,000 0.040

ULF Toilet - Business 1,411 0.148

Low-flow Urinals - Business 16 0.001

Clothes Washer - Business 26 0.001

Showerhead Promotions - Business 1,000 0.046

TOTAL (mgd) 0.62

At first glance, a reduction of 0.62 mgd of wastewater generated by customers might not seem significant. However, construction costs for new wastewater treatment capacity can be in the range of $10/gallon. This means that a 0.62 mgd reduction of wastewater generated by customers is worth $6.2 million dollars of new treatment capacity (600,000 gal x $10/gal = $6.2 million).

In addition to water use reduction from indoor fixture rebates, changes to the Plumbing Code were made in 1999. One example is low-flush toilets. All new toilets have to meet the low-flush volume criterion. As older toilets are replaced with low-flush toilets, further wastewater volume reductions will occur over time.

During the 2002 drought, watering restrictions reduced excess watering of lawns. Some collection system infiltration comes from lawn irrigation where overwatering can result in irrigation water entering service lines. It is difficult to quantify the reduction of infiltration due to less overwatering of lawns. But this is another potential factor in the story of reduced influent flows at LVSWWTF.

Even though the population served by the LVSWWTF has increased over the past 10 years, influent flows have decreased because of lower than average rainfall for six of the past seven years, extensive collection system rehabilitation efforts, and water conservation efforts. From a planning perspective, this trend complicates making growth predictions.


PAGE 3-10 DRAFT – Dec. 31, 2008

3.1.2.2.3. Banning Lewis Ranch Currently flows from the Banning Lewis Ranch (BLR) Development are being treated at LVSWWTF. The great majority of future development in Colorado Springs will occur on BLR. Current negotiations with BLR are aimed at finding mutually beneficial options resulting in lower costs for both BLR and the Utilities. One strategy involves delaying the construction of additional capacity at LVSWWTF until adequate homes have been built at BLR. If interim capacity of 4 mgd can be found, this will provide adequate buffer before a significant plant expansion is needed. Currently the JDPWRF has excess capacity (20 mgd capacity but only treating 6-7 mgd). A lift station could be installed to divert 4 mgd of flow from LVSWWTF to JDPWRF. Wastewater characterization of diversion flows is being conducted in 2008. The diversions will be evaluated with a computer based model called BioWin to ensure that the diversions do not adversely affect either of the wastewater treatment facilities.

3.1.2.2.4. Future Population and Influent Flow Projection After JDPWRF started discharging in May 2008, the average influent flow at LVSWWTF obviously decreased as flow that previously came to LVSWWTF was treated and discharged by JDPWRF. During June and July of 2008, influent flow at LVSWWTF was averaging 35 mgd.

A collection system model developed by MWH and updated in 2008 calculates flow predictions for LVSWWTF (Table 3-5). The model is predicting an annual average influent flow in 2008 of 38.3 mgd for the LVSWWTF. This is reasonable given that wet weather flows are likely to drive the annual average flow for 2008 higher than the current 35 mgd. The collection system model takes into account population growth, hydrographs and time of concentration. The model predicts that flow will increase to 43.3 mgd by 2020 and 46.5 mgd by 2030.

Table 3-5 – LVSWWTF Dry Weather Flows Predicted by the Collection System Model

Year Flow (mgd) Population

2008 38.3 322,771

2020 43.3 376,278

2030 46.5 417,427

Figure 3-7 plots historical population and flows along with the predicted population and flow from the collection system model. It should be noted that in 2008, the population served by the LVSWWTF and influent flow decreased significantly because JDPWRF started treating and discharging wastewater (6-7 mgd). Figure 3-4 also provides a historical reality check for the future predictions. Historical influent flow increases from 1990 to 1997 are larger than what the model is predicting for flow increases from 2008 to 2020. Slower population growth and slower increases in influent flow are expected due to the fact that developable land area in the basins served by LVSWWTF is limited. The majority of future growth will be occurring on the north and east sides of Colorado Springs. The future population and flow predictions in Figure 3-4 include aggressive development assumptions for BLR. Given the current slowdown in housing development, it is likely that


PAGE 3-11 DRAFT – Dec. 31, 2008

the projected flows in Figure 3-4 are on the high side (but more rapid development in the future may occur and make up some of the ground).

Another method of predicting future flows is to use forecasting software. Springs Utilities uses forecasting software to predict demands for water, natural gas, and electricity. In 2009, this software will be used to predict wastewater flows taking into consideration population projections and the increased use of water-efficient fixtures and appliances.

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Future Population and Influent Flow Prediction from 2008 Collection System Model - Includes all flow from Banning Lewis Ranch with aggressive develop-ment assumptions

Figure 3-7 – Historical Population, Influent Flow Data and Future Predictions

The current rated capacity of LVSWWTF in the months of January and February is 65 mgd. Design of additional treatment capacity needs to start when flows reach 80% of capacity. For the LVSWWTF, design would need to start when flows reach 52 mgd. Projected flow in 2030 according to Figure 3-4 is 46.5 mgd. Therefore, design for plant expansion is not expected to occur before 2030 based on flow projections. However, permit requirements may drive the plant to make process improvements.

3.1.3. Facility Improvements Capital improvement projects in some cases are required due to regulatory drivers. In other cases process improvements increase the efficiency of the process that leads in the long term to lower operation and maintenance costs. In addition, some plant components are old and approaching the end of their useful life.


PAGE 3-12 DRAFT – Dec. 31, 2008

3.1.3.1. Disinfection Peak flow at LVSWWTF before JDPWRF came on-line ranged between 50 and 70 mgd. Chlorine is used to disinfect the wastewater effluent in contact basins. The two chlorine contact basins have a combined capacity of 80 mgd. The disinfection system was designed to operate using one basin with the second as backup with a goal of 30 minutes of contact time. A single basin cannot provide 30 minutes of contact time during peak flows. However, the existing system has complied with permit limits to date and operation with one basin in service has been approved by the State.

In 2011, the operating permit for LVSWWTF will be renewed. The current limit uses fecal coliforms as the indicator organism for demonstrating compliance. The new limit will use E. coli as the indicator organism.

Recent testing of the chlorine disinfection system simulating compliance with lower future limits showed that the current system does not consistently meet the future limits. The testing also showed that operating both basins at the same time to try to increase contact time is difficult hydraulically because the influent channel was not designed to balance flows between the two basins over the range of flows that the plant experiences. The testing showed the need for an evaluation of disinfection alternatives.

In September and October of 2008, a decision-making process was undertaken to evaluate the best disinfection technology to use at the LVSWWTF. Alternatives that were considered included ultra-violet (UV) light, ozone, and sodium hypochlorite disinfection technologies and upgrading of the existing chlorine system. In addition to evaluating life-cycle costs, factors such as safety, reliability, ease of operation, regulatory burden and reporting, etc. were given weighting and an overall score was determined for each alternative. The best alternative for the plant was determined to be installation of a UV disinfection system. In early 2009, a design firm will be selected. The engineering firm will analyze whether it is best to install the UV system in one of the current chlorine contact basins, or if it will be better to locate the UV system in a new structure. Construction of the UV system will be undertaken in 2009 and 2010. The UV system will be fully functional by February 11, 2011 to enable the plant to comply with disinfection requirements in the 2011 permit.

3.1.3.2. Primary Backup Pumps Flow from the primary sedimentation tanks is pumped up into the Sky Flume Channel so that wastewater can flow by gravity through the rest of the plant. The current pumping configuration includes two electric pumps and two backup natural gas pumps that are put into operation in cases of electrical outage, failure of the electric pumps or if needed for short term spikes in flow. The natural gas engines are old and parts are difficult to find. The engines are located on a separate foundation from the pumps and are connected via a fixed drive shaft. Over time the foundation for the engines has settled. This has created differential settlement with respect to the foundation supporting the pumps. Due to the differential settlement vertical stress has been placed on the drive shaft. Since the engines are only used as back up, failure of the shafts has not occurred. In the event of an outage or failure of the electric motors the natural gas pumps would need to be operated. Under this scenario the drive shafts could prematurely fail with no back up available. The


PAGE 3-13 DRAFT – Dec. 31, 2008

loss of pumping would prevent any effluent from being pumped up to the Sky Flume and through the remaining process and the outfall.

Another problem with the natural gas engines is that they have a very limited operating range and have to run at close to full power. The current plan is to replace the natural gas engines with new natural gas engines that also have variable speed drives. One pump will be replaced in 2009, and the second one will be replaced in 2010.

3.1.3.3. Grease Handling Fats, Oil and Grease (FOG) are generated during food preparation, equipment maintenance, and food-service sanitizing processes. FOG sources include commercial, industrial and residential activities in the Utilities collection system. FOG are a component of the wastewater influent at the treatment facilities.

Another significant source of FOG comes from septic tank pumping in and around the service area which are disposed of at the Liquid Waste Receiving Station at the LVSWWTF. Septic loads are unique in their wastewater characteristics because they are significantly heavier in loading of waste material than normal wastewater produced in the service area. These can include FOG that has attached to food and waste particles in septic tanks. These particles end up directly at the headworks of the LVSWWTF in a concentrated form, and have the potential to cause additional blockages, stoppages and maintenance.

Collection system grease and FOG from septic haulers result in a substantial amount of grease at the headworks of the LVSWWTF. While an exact loading figure for FOG is not known, the loading at the LVSWWTF recently amounted to a tanker truck of grease and grease-laden material approximately every 10 days.

Impacts of FOG at the LVSWSWTF include influent screens lined with grease, decreased pipe throughput at the headworks from grease accumulation, and settling of grease which forms into large clumps or bricks in the primary sedimentation basins. Each of the situations requires extra maintenance to ensure optimal operation of the respective treatment processes and infrastructure.

In 2008, an experiment was undertaken to see if the grease that is collected at the headworks of the LVSWWTF could be injected into the pipeline that conveys sludge to the Solids Handling and Disposal Facility located at Clear Spring Ranch. Greater volumes of gas appeared to be generated in the pipeline as a result of injecting the grease. This required the adjustment of some valves at SHDF to handle gas volumes that entered the wet well at SHDF. The successful experiment has eliminated the need haul grease via tanker truck from LVSWWTF to SHDF. This is a significant accomplishment because the tanker trailers were reaching the end of their useful life. They will not need to be replaced.

The grease concentrator that allows grease to be separated from conveyance water need to be upgraded and moved to a location adjacent to piping that conveys biosolids to SHDF. This project is scheduled to be completed in 2009.

Alternatives for reducing grease loading at LVSWWTF are discussed below in Section 3.1.5. Reduction of FOG in the collection system is discussed in Section 2.4.


PAGE 3-14 DRAFT – Dec. 31, 2008

3.1.3.4. Sky Flume Concrete Repair Effluent flow from the primary sedimentation tanks is pumped into the Sky Flume, which is an elevated channel from which wastewater can flow by gravity through the rest of the plant. A tremendous amount of hydrogen sulfide is stripped from the wastewater in the outfall structure of the Sky Flume. The air in the headspace between the wastewater and covers of the Sky Flume is treated by an odor control system that removed the hydrogen sulfide and other odorous compounds from the treated airstream.

However, hydrogen sulfide that is stripped from the wastewater in the outfall structure of the Sky Flume is converted by bacteria on concrete surfaces to sulfuric acid. The acid attacks the concrete, and over time spalling of the concrete occurs, the weakened concrete falls off, allowing acid attack of the newly exposed surface. The underside of the concrete lid of the outfall structure has been degraded by sulfuric acid to the point where it needs to be removed and replaced with a cover that is inert to acid attack.

Other areas of the Sky Flume walls have been protected with the application of a coating to the concrete surface that protects it from acid attack. This option was considered for the lid of the outfall structure as well, but the coating cannot be safely applied due to the fact that the outfall structure cannot be taken out of service for a long enough period of time to apply to coating. Also the outfall structure does not allow for placement of scaffolding or other support structures for workmen to apply the coating.

The concrete lid needs to be cut free and removed. The replacement lid will be either aluminum decking or structural fiberglass panels. Due to the disastrous impact a collapse of the concrete lid could have on restricting flow to the rest of the plant, this project is necessary to complete in 2009.

3.1.3.5. Metering and Controls Influent flow and effluent flow to Fountain Creek are measured by ultrasonic instruments in Parshall flumes. Ultrasonic instruments mounted above the flumes record the water surface elevation and software calculates flow based on calibration curves.

Characterization of flows at LVSWWTF is complicated by the fact that some flows are re-circulated within the plant between the flumes and are not metered. Metering of these flows would allow for better comparisons of influent and effluent flow.

3.1.3.6. Bioplant Evaluation The Bioplant has not been operated since 1998. Uncertainty about the operational condition of equipment exists and will be assessed in 2009. Also in 2009, historical operation data will be analyzed to see if blending the effluent from the Bioplant with the AWT effluent will meet new lower permit effluent limits that will take effect in 2011.

As budgets allow, a further analysis may be undertaken in 2009 to look at optimizing expansion of flows in the AWTs and see if the Bioplant can provide useful capacity at lower flow rates. This combination may turn out to be a long term strategy if the analysis indicates that both sides of the plant can operate to meet permit limits.


PAGE 3-15 DRAFT – Dec. 31, 2008

3.1.4. Regulatory Evaluation The regulatory picture currently has a degree of uncertainty associated with it. The LVSWWTF permit is up for renewal in 2011. New permit limits are expected as a part of the permit renewal process. Work is being undertaken in 2008 to estimate what the new limits will be. However, the assumptions and approaches used in the 2008 work are subject to Colorado Department of Public Health & Environment (CDPHE) review. Only after CDPHE review and approval will there be certainty about the 2011 permit limits.

Several factors are driving new permit limits in 2011. First the CDPHE has changed the computer based model used to calculate effluent limits for ammonia based on the receiving stream characteristics. The updated ammonia model is called AMMTOX and calculates effluent limits taking into account other permitted discharges to Fountain Creek.

Second, the stream segment (Stream Segment 2a of the Fountain Creek Sub-basin) that LVSWWTF discharges into was, until recently, classified as “Use Protected”. When the stream segment is classified as “Use Protected” permit effluent limits are calculated based on stream standards and the assimilative capacity of the stream segment. In July of 2008, the classification of Stream Segment 2a changed to “Reviewable”. For stream segments that are “Reviewable” an antidegradation analysis has to be conducted to determine whether new or increased impacts are expected at the time of permit renewal and for plant expansions. The analysis may result in new limits that are designed to prevent higher loading of pollutants into the receiving stream and may be lower than the plant’s limits prior to permit renewal or expansion.

As new water quality standards for streams are developed, they will drive new permit limits for wastewater treatment plants. In 2010 a stream standard for nonylphenol (a chemical used in surfactants, soaps, etc.) may be passed. Also nutrients such as nitrogen and phosphorous are receiving attention from the EPA. New limits may result from ongoing studies in these areas.

3.1.4.1. Existing Permit Limits Effluent limits that are expected to change in the 2011 renewal process and can impact operations at LVSWWTF include ammonia, fecal coliform bacteria, and possibly some metals.

3.1.4.1.1. Ammonia Limits The current effluent limits for ammonia vary by month and range from 3.2 to 5.3 mg/l. The months with the lowest limits include March, August and September.

3.1.4.1.2. Fecal Coliform Limit The current disinfection effluent limit uses fecal coliforms as the indicator organism to demonstrate compliance. The 7-day average is 400 CFU/100 mL, while the 30-day average is 200 CFU/100 mL.

3.1.4.1.3. Metals Limits The LVSWWTF currently has 30-day average limits for chromium, copper, lead, mercury, and nickel. The plant needs to measure and report selenium data. Iron (dissolved and total recoverable) and dissolved manganese are also being measured and reported.


PAGE 3-16 DRAFT – Dec. 31, 2008

3.1.4.2. Projected Permit Limits An estimate of the expected 2011 permit limits has been completed in 2008.

3.1.4.2.1. Ammonia Limits With the introduction of the AMMTOX model by the CDPHE for determining effluent ammonia limits for wastewater treatment plants, most plants will be receiving lower limits in their next permit renewal cycle. If the AMMTOX model is run with downstream dischargers modeled with their current effluent limits, the model yields several months of the year where the LVSWWTF would have a zero limit. This is not feasible.

Therefore the model was run again with the assumption that downstream users would be held to their maximum historical discharge concentration as their modeled permit limit. This approach will need to be discussed with the CDPHE before much certainty is placed in the results. Table 3-6 shows the current monthly effluent ammonia limits and the potential 2011 limits. Recent permit information from a couple of downstream plants indicates that they are receiving lower limits for ammonia than their maximum historical discharge concentrations. As plant downstream receive lower ammonia limits than their historical maximum discharge concentrations, it allows for LVSWWTF to receive higher discharge limits. This is because the ammonia loading on Fountain Creek is shared by all the plants along the creek. Therefore the potential ammonia limits in Table 3-6 are likely to be worst case values.

Based on recent operational data from LVSWWTF, it appears that the plant will be able to comply with these estimated 2011 ammonia limits without the installation of process improvements for ammonia removal. This may change if the CDPHE takes a significantly different approach to establishing the ammonia limits.

Table 3-6 – Monthly Effluent Ammonia Limits for LVSWWTF

Month Current Potential 2011

January 5.3 2.8

February 5.3 3.0

March 3.6 2.5

April 4.1 2.7

May 4.7 2.7

June 5.3 3.4

July 4.7 2.9

August 3.9 3.0

September 3.2 2.8

October 5.1 2.7

November 4.0 2.7

December 5.2 2.8


PAGE 3-17 DRAFT – Dec. 31, 2008

3.1.4.2.2. E. coli Limits Stream Segment 2a of the Fountain Creek Sub-basin that the LVSWWTF discharges into carries a fairly high ambient concentration of E. coli. When the ambient water quality exceeds the water quality standard, the effluent limit is set equal to the water quality standard. The water quality standard for E. coli for Stream Segment 2a is 126 CFU/100 mL (30 day average). The 7 day average is 252 CFU/100 mL. These are the expected effluent E. coli limits for the 2011 permit.

3.1.4.2.3. Metals Limits Table 3-7 lists the current effluent limits for metals and the 2011 limits that have been calculated. Little change is expected for the metals that already have 30-day average effluent limits. The plant may receive shorter term limits for the six metals listed in Table 3-7. Analysis is being undertaken to see if shorter term limits pose a concern for compliance.

Table 3-7 – Monthly Metals Limits for LVSWWTF

Metal Current 30-Day Avg.

Potential 2011 30-Day Avg.

Chromium (µg/L) 12 12

Copper (µg/L) 20 20

Lead (µg/L) 6.6 6.6

Mercury (µg/L) 0.011 0.010

Nickel (µg/L) 112 114

Selenium (µg/L) Report 8

New effluent limits may be imposed for boron, silver, arsenic, cadmium, iron, manganese, and zinc. Potential limits have been calculated for these parameters. In 2009, a comparison of recent historical effluent concentrations will be made to these potential future limits to see if any of them cause concern for compliance. For some of the metals, the Industrial Pre-treatment Program may need to take a role in reducing industrial discharge of certain metals to help with permit compliance.

3.1.4.3. Strategy to Meet New Permit Limits

3.1.4.3.1. Ammonia Limits If the CDPHE takes a different approach than Springs Utilities in calculating the 2011 effluent ammonia limits and gives the plant much lower limits, then at that time, negotiations will need to occur. A compliance schedule for implementing any necessary treatment process improvements will be drawn up.

3.1.4.3.2. E. coli Limits

A decision making process was undertaken in the 3rd quarter of 2008 that evaluated disinfection alternatives. Selection of the best alternative was determined to be ultraviolet (UV) light disinfection. Construction of the UV disinfection system will take place in 2009


PAGE 3-18 DRAFT – Dec. 31, 2008

and 2010. The UV system will be on-line in 2011. The design criteria will ensure that the UV system will be capable of consistently disinfecting the plant effluent to meet the 2011 permit limits.

3.1.4.3.3. Metals Limits If one or two of the new 2011 effluent metals limits present a challenge for compliance, it is likely that the metals can be addressed through the industrial pre-treatment program. If industries are kept from discharging the problem metal, it will reduce the concentration that the plant has to deal with.

3.1.5. Alternatives Development

3.1.5.1. Disinfection Alternatives Several alternatives have been considered in the decision-making process that was undertaken in 2008. Upgrading the existing chlorine system was considered along with ultraviolet light (UV), ozone, and sodium hypochlorite. Multiple criteria were scored to select the best alternative, which turned out to be a UV system. Design is expected to take place in 2009 with construction taking place in 2009 and 2010. The UV system is expected to be on-line and fully functional before February 11, 2011, the date of the next permit renewal for LVSWWTF.

3.1.5.2. Grease Handling Alternatives Treatment alternatives are being explored in 2008-2010 to determine opportunities to reduce grease accumulation at the LVSWWTF due to FOG inputs from the Liquid Waste Receiving Station. Alternatives center around a FOG-removal step immediately down-stream of the Liquid Waste Receiving Station which would remove FOG before it has a chance to enter the LVSWWTF headworks. These include:

- possibly banning combined grease/septic loads. Liquid waste haulers are permitted to combine septic loads with grease trap/interceptor pumpings from food service establishments. Limiting this practice may make it easier to control the fate of grease pumpings from food service establishments.

- offering financial incentives. Decreasing the disposal costs for grease loads may encourage haulers to take the grease loads directly to the Solids Handling and Disposal Facility for processing in the facility’s digesters, thus preventing the grease from entering the LVSWWTF.

Another alternative being explored is potential relocation of the Liquid Waste Receiving Station to another location in the collection system, or to the Solids Handling and Disposal Facility, or to route septage flow to a different location at LVSWWTF.

Additional efforts are being directed toward recycling fryer oils and brown grease in the collection system for use as feed stock in biodiesel and/or methane production. While these opportunities are in their infancy, several projects are underway to determine potential renewable sources of energy from these waste products. Recycling of FOG before it enters the collection system will directly reduce the FOG loading at LVSWWTF.


PAGE 3-19 DRAFT – Dec. 31, 2008

3.1.5.3. Back Up Pumping at Sky Flume Alternatives An alternatives analysis was completed in June of 2006. Three alternatives were evaluated. Alternative #1 looked at overhauling existing pumps only. Alternative #2 looked at overhauling existing motors and adding a pump with a 30 MGD capacity. Alternative #3 examined replacing the aging natural gas pumps with electric pumps. Currently plant staff are planning on replacement of the natural gas pumps with new natural gas powered pumps that are variable speed with a 60 mgd capacity. The reason for this is that natural gas provides a more robust source of backup energy supply when power outages are experienced at the plant. Money has been budgeted in 2009 to replace one backup pump with the second pump being replaced in 2010.

3.1.5.4. AWT Improvement Alternatives A computer-based model called BioWin is being developed in 2008. The model simulates performance of the wastewater treatment plant. Once the model has been calibrated and been shown to reasonably predict plant performance, then it can be used to simulate process improvements. Alternatives development will be undertaken in 2009 or 2010 depending on budget constraints.

3.1.6. Capital Improvements and O&M Program

3.1.6.1. 10-Year Capital Improvements Plan This Masterplan at this point only captures capital improvement projects that are major projects. Smaller capital projects may be included in future editions of this Plan.

There are five major capital projects planned for construction in the next 10 years. These include disinfection system improvements, AWT improvements, primary pump replacements, grease concentrator improvements, and replacement of the outfall structure lid on the Sky Flume. Table 3-8 lists the projects and the budgeted amounts.

Table 3-8 – Budgeted Amounts for Capital Projects at LVSWWTF (in millions)

Projects 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018

Disinfection $1.35 $9.75 $0.97 $0 $0 $0 $0 $0 $0 $0

AWT Improvements $0 $0 $0 $1.00 $5.20 $5.00 $3.72 $0 $0 $0

Primary Pump Replacement

$0.25 $0.25 $0 $0 $0 $0 $0 $0 $0 $0

Grease Concentrator $0.70 $0 $0 $0 $0 $0 $0 $0 $0 $0

Sky Flume Concrete Repair

$0.35 $0 $0 $0 $0 $0 $0 $0 $0 $0

Various Small Projects $0.24 $0.19 $0.95 $0.04 $0.32 $0.30 $0.19 $0.14 $0.30 $0.60

Total $2.89 $10.2 $1.92 $1.04 $5.52 $5.30 $3.91 $0.14 $0.30 $0.60

3.1.6.2. 10-Year O&M Improvements Plan Major Operation & Maintenance (O&M) projects include studies that are necessary for capital projects and major expenses for O&M projects at the plant. An alternatives analysis for AWT improvements will be conducted in 2009 or 2010 depending on budget constraints.


PAGE 3-20 DRAFT – Dec. 31, 2008

For odor control systems at the plant, replacement of the media occurs at regular intervals. In the odor control systems, foul air is blown through a dual stage media bed where one type of media removes hydrogen sulfide gas, and an activated carbon layer polishes the remaining odors in the airstream. A seven year cycle for media replacement occurs for the Bar Screen Room. The replacement cycles for two other odor control systems are estimated at this time because they have not yet been taken through their first replacement cycle.

Table 3-9 – Budgeted Amounts for Extraordinary O&M Projects at LVSWWTF (in thousands)

Projects Total 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018AWT

Improvement $200k $200k $0 $0 $0 $0 $0 $0 $0 $0 $0 Odor Control $280k $100k $107.8k $9.4k $62.8k $0 $0 $0 $30 $0 $0

3.2. J.D. Phillips Wastewater Reclamation Facility

3.2.1. Description The JDPWRF serves the northern part of Colorado Springs. A large amount of development has occurred on the north side of Colorado Springs. In order to convey wastewater from the north to the LVSWWTF, extensive upgrade of the collection system through the Monument Creek corridor would have been required. This was avoided by locating JDPWRF to receive flow from the north part of Colorado Springs. In addition, the location of the plant reduces risks due to flood impacts to the Monument Creek corridor.

The J.D. Phillips Water Reclamation Facility (JDPWRF) currently has a hydraulic capacity of 20 mgd. The facility can be expanded in the future to 30 mgd. The JDPWRF is a conventional activated sludge advanced wastewater treatment plant with full biological nutrient removal and ultraviolet radiation disinfection facilities serving the northern part of Colorado Springs.

Preliminary treatment includes screenings removal utilizing five mechanical step screens, followed by two aerated grit chambers and two rectangular, chain and flight type, primary sedimentation tanks. Additionally, the plant includes an 11-mgd AquaDisk® tertiary filter system (expandable to 22 mgd) for on-site and external reclaimed water use, a comprehensive odor management system utilizing chemical wet scrubbers followed by carbon absorption, and covered treatment units to aid with odor control and increase the aesthetics of the facility. Ultraviolet (UV) disinfection completes the process prior to discharge into nearby Monument Creek.

3.2.2. Facility Condition and Capacity Evaluation The JDPWRF started discharging treated effluent in May of 2008. With the plant being brand new and functioning well, it is in great condition. Average flow currently is 6-7 mgd. The rated hydraulic capacity is 20 mgd. In the near future, an additional 4 mgd may be diverted from LVSWWTF and pumped to JDPWRF to take advantage of the excess capacity at JDPWRF.


PAGE 3-21 DRAFT – Dec. 31, 2008

The 30-day average organic capacity is 51,374 lbs/CBOD5 per day. Recent influent testing showed the CBOD5 average daily value was 353 mg/l. This equals 11,785 pounds per day of CBOD5, which is well below the rated organic loading capacity.

3.2.3. Future Capacity Requirements Analysis A collection system model developed by MWH and updated in 2008 calculates flow predictions for JDPWRF (Table 3-10). The collection system model takes into account population growth, hydrographs and time of concentration. Current influent flow at JDPWRF is averaging 6-7 mgd. Even with an additional 4 mgd, due to a possible diversion of flow from LVSSWTF, capacity issues should not be encountered before 2030 based on hydraulic loading. In addition, the organic loading of the plant is not a concern in the planning horizon of this document.

Table 3-10 - JDPWRF Dry Weather Flows Predicted by the Collection System Model

Year Flow (mgd) Population

2008 8.8 106,907

2020 9.4 122,291

2030 10.3 135,301

3.2.4. Regulatory Evaluation The JDPWRF discharges treated effluent to Monument Creek – Stream Segment 6 in the Fountain Creek Basin of the Arkansas River. In July of 2008, this stream segment was reclassified to “Reviewable” from “Use Protected”. This means that an antidegradation analysis will have to be conducted for any future plant expansions and permit renewals.

Permit limits are being met by JDPWRF. The plant’s next permit renewal will occur in 2011. As new water quality standards for streams are developed, they will drive new permit limits for wastewater treatment plants. In 2010 a stream standard for nonylphenol (a chemical used in surfactants, soaps, etc.) may be passed. Also nutrients such as nitrogen and phosphorous are receiving attention from the EPA. New limits may result from ongoing studies in these areas.

3.2.5. Capital Improvements and O&M Program

3.2.5.1. 10-Year Capital Improvements Plan Because the JDPWRF just came on-line in 2008, no major capital improvements are currently planned for the next 10 years.

3.2.5.2. 10-Year O&M Improvements Plan Extraordinary O&M improvements are not currently planned 10 years in advance.

WASTEWATER INTEGRATED MASTERPLAN SOLIDS HANDLING & DISPOSAL FACILITY MASTERPLAN

PAGE 4-1

DRAFT – Dec. 31, 2008

4. SOLIDS HANDLING & DISPOSAL FACILITY MASTERPLAN

Located 17.6 miles southwest of downtown Colorado Springs on the 5,000 acre Clear Spring Ranch, the Colorado Springs Utilities’ Solids Handling & Disposal Facility (SHDF) collects, stabilizes, stores, and disposes of all sewage sludge (biosolids) produced at the Las Vegas Street Wastewater Treatment Facility (LVSWWTF) and the J.D. Phillips Water Reclamation Facility (JDPWRF). Figure 4-1 shows the location of the LVSWWTF and SHDF and the sludge pipeline that connects the two facilities.

Figure 4-1 – Sludge Pipeline Connecting LVSWWTF and SHDF


PAGE 4-2

DRAFT – Dec. 31, 2008

Grit removed from wastewater at LVSWWTF is also disposed of at the SHDF. Since start-up in 1984, the SHDF has consistently met treatment objectives and is a well-managed and efficient operation.

4.1. Description

As was mentioned earlier, a 17.6 mile pipeline conveys the sludge to the digester complex at SHDF where the biosolids undergo anaerobic digestion and then are stabilized in Facultative Sludge Basins (FSBs). Stabilized biosolids are sub-surface injected into dedicated land disposal units (DLDs) for final disposal. An aerial photograph of the facility is presented in Figure 4-1. A terragator vehicle which is used for sludge injection is also shown in Figure 4-2.

Figure 4-2 – Solids Handling Facility

The facilities at the SHDF currently consist of eight anaerobic digesters that reduce volatile solids to produce stable sludge, the Energy Recovery building, Equipment Operations building, nine Facultative Sludge Basins (FSBs) for further biological treatment and storage of the anaerobically digested solids which are pumped from the digesters, Dedicated Land Disposal areas (DLDs) for disposal of the stabilized sludge by subsurface injection, and two Supernatant Lagoons for disposal of the supernatant from the FSBs.


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4.2. Facility Condition and Capacity Evaluation

In this section, a condition and capacity evaluation of the Blended Sludge Pump Station (BSPS), Sludge Pipeline, Aerobic Digesters, Facultative Sludge Basins (FSBs), and Dedicated Land Disposal Units (DLDs) is presented.

The top priority for capital expenditure in the next 10 years is to rehabilitate the four old anaerobic digesters. Although the digester complex has excess hydraulic capacity until at least 2014, the old digesters have components that are reaching the end of their useful life. Replacement of the floating covers and other components will need to be carried out before hydraulic capacity issues arise in 2014.

The second priority for capital funds revolves around the FSBs. Additional FSB capacity will need to be installed in the next 10 years, or a more sustainable and efficient means of disposing of the solids will need to be investigated.

4.2.1. Blended Sludge Pump Station The Blended Sludge Pump Station (BSPS) is located at the LVSWWTF. This unit handles a combination of primary and secondary sludges from the activated sludge process train. It should be noted that sludge from JDPWRF is conveyed through the collection system to the LVSWWTF. Most of the JDPWRF solids settle in the primary sedimentation tanks at LVSWWTF.

The BSPS is equipped with 3 piston diaphragm pumps that convey the sludge to the SHDF. Each pump has a capacity of 175 gpm at an average solids concentration of approximately 3.1 percent (dry solids).

With two of the pumps in continuous service and one in standby, the total pumping capacity is 504,000 gallons per day. In terms of future flow projections, if it is assumed that flow will increase by the average of the increases observed in 2003 and 2004 (i.e. 16,000 gallons per year) and that the increases will start in 2010 and be linear from then on, then the resulting projected flows are presented in Table 4-1. According to this projection, additional pump capacity may be of concern in the year 2021. This is beyond the 10-year planning horizon for capital funds that this document is aimed at. In addition the assumption of linearly increasing flows is likely to be quite conservative when the history of flows in Figure 4-1 is examined.

Table 4-1 - Projected Future Flows for BSPS Capacity

Year Flow (gal)

2007 322,400

2008 322,400

2009 322,400

2010 338,400

2011 354,400

2012 370,400

2013 386,400

2014 402,400

2015 418,400


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DRAFT – Dec. 31, 2008

Year Flow (gal)

2016 434,400

2017 450,400

2018 466,400

2019 482,400

2020 498,400

2021 514,400

4.2.2. Sludge Pipeline The Sludge Pipeline conveys sludge from the BSPS at the LVSWWTF to the SHDF. The 14-inch diameter fiberglass pipeline extends for 17.6 miles and has a capacity of approximately 700,000 gallons per day. The capacity of the line is not expected to be exceeded until some time after 2030.

4.2.3. Anaerobic Digesters There are four older digesters that became operational in 1984 and four newer digesters that became operational in 2000. The characteristics of the two sets of digesters are summarized in Table 4-2.

All the digesters are operated as primary mixed units in parallel and are provided with a drainage pumping station that can be used for pumping the digested sludge to the FSBs, draining the digester tanks, or transferring sludge between tanks. Circulating sludge lines and pumps are provided for internal mixing and heating of sludge for each digester.

Table 4-2 - Digester Characteristics

Characteristics “Old” Digesters (1984) “New” Digesters (2000)

Volume 1.4 million gal. 1.8 million gal.

Number 4 4

Cover Type Floating Submerged-Fixed

Mixing System Re-circulated Gas Draft Tubes

Digester performance involves the analysis of several parameters such as, average flow rates into the digesters, hydraulic detention time, solids loading rate, and volatile solids reduction. Flow rates into SHDF have been plotted in Figure 4-3 for both monthly averages and annual averages. Figure 4-3 also shows the monthly and annual average influent flow rates to the LVSWWTF. The annual flow rates appear to be correlated, but the monthly average flow rates at the two facilities are not as closely correlated.

The annual average flow rates have decreased in 2005, 2006 and 2007. Year-to-date flows in 2008 appear to be headed for a lower annual average than 2007. The decrease in flows is related to the decrease in flows at LVSWWTF. As was discussed earlier for the LVSWWTF, wastewater flows have decreased in recent years because of lower per capita water use, decreased infiltration from slip-lining collection pipes and below average rainfall for seven out of the last eight years, and installation of fixtures


PAGE 4-5

DRAFT – Dec. 31, 2008

and appliances that use less water. Lower flows at LVSWWTF translate into lower flows at SHDF. Another factor involved in sludge flow rates is primary sedimentation tank (PST) improvements at LVSSWTF that were made over several years from 2005 to 2007. The improvements allow for better control of the sludge blanket at the bottom of the PSTs and for more consistent pumping rates. In the past, variability in sludge blanket depths and variable pumping rates led to wider swings in monthly average flows as can be seen in the data from 2001 to 2005 in Figure 4-3.

Monthly Average Influent Flow to SHDF (2001 to 2007)

150000

200000

250000

300000

350000

400000

2001

2002

2003

2004

2005

2006

2007

J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D

Date

Infl

ue

nt

Flo

w (

Ga

llo

ns

)

32

37

42

47

52

57

LV

SW

WT

F F

low

(m

gd

)

Monthly Average Flow (gal)

Annual Average Flow (gal)

LVSWWTF Monthly Avg Flow (mgd)

LVSWWTF Annual Flow (mgd)

Figure 4-3 – Comparison of Monthly Average Influent Flows between SHDF and LVSWWTF

Hydraulic detention time is the number of days that sludge stays in a digester before it is discharged to the facultative sludge basins (FSBs). The permit for SHDF requires that sludge remain in a digester for a minimum of 15 days if the temperature of the sludge is maintained above 35 ºC to achieve Class B quality. The detention time for each digester is calculated and logged each day.

The annual average detention time for all the digesters in operation at SHDF is presented in Table 4-3 for the years 2001-2007. The reason for the large increase in detention time between 2001 and 2002 is that in 2002 an additional digester was put on-line. In 2001 four digesters were operating, while from 2002 on, five digesters have been in operation. With the average detention time from 2002 to 2007 being above 25 days, the minimum requirement of 15 days has been met and exceeded.

Another variable that needs to be analyzed in determining digester performance is the volatile solids loading rate. The sludge that leaves LVSWWTF and flows through the pipeline to SHDF is mostly water with only a few percent solids. The solids are made up of an inert portion that passes through the digesters and a volatile portion that can


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DRAFT – Dec. 31, 2008

be treated in the digester. The volatile solids are consumed by bacteria and converted to gases like carbon dioxide, hydrogen sulfide, and other compounds, such as ammonia, etc. The mass of volatile solids are reduced in the digesters.

Table 4-3 - Annual Average Flow and Digester Retention Time

Year Annual Average

Flow (gal) Annual Average

Detention Time (days) 2001 341,314 21.6 2002 330,782 26.1 2003 345,350 25.1 2004 362,712 25.7 2005 348,029 25.2 2006 339,521 25.7 2007 322,396 27.2

The volatile solids loading rates are calculated by dividing the pounds of volatile solids that come into SHDF by the capacity of the digesters. The loading rate units are in pounds of volatile solids per day per cubic feet of digester capacity. The first thing to determine is the digester capacity. Table 4-4 presents a list of the digesters and how many days they were on-line during a given year. Four digesters were on-line in 2001, but from 2002 onward, five digesters have been on-line. Due to maintenance activities, there are periods of time when not all five of the digesters are on-line, and this is why the total number is less than five for each year.

Table 4-4 – Number of Digesters On-line

Year Parameter Digester Total

#1 #2 #5 #6 #7 #8 Digesters

Days On-line 0 19 365 365 364 283 ------------ 2001

Annual Fraction 0.00 0.05 1.00 1.00 1.00 0.78 3.82

Days On-line 361 365 365 365 365 0 ------------ 2002

Annual Fraction 0.99 1.00 1.00 1.00 1.00 0.00 4.99

Days On-line 365 365 350 365 134 206 ------------ 2003

Annual Fraction 1.00 1.00 0.96 1.00 0.37 0.56 4.89

Days On-line 224 366 245 217 359 349 ------------ 2004

Annual Fraction 0.61 1.00 0.67 0.59 0.98 0.95 4.81

Days On-line 359 108 365 365 263 309 ------------ 2005

Annual Fraction 0.98 0.30 1.00 1.00 0.72 0.85 4.85

Days On-line 182 365 230 318 283 365 ------------ 2006

Annual Fraction 0.50 1.00 0.63 0.87 0.78 1.00 4.78

Days On-line 98 365 365 267 304 365 ------------ 2007

Annual Fraction 0.27 1.00 1.00 0.73 0.83 1.00 4.83


PAGE 4-7

DRAFT – Dec. 31, 2008

Because Digesters #1 and #2 (1.4 million gallons) have different capacities from Digesters #5 through #8 (1.8 million gallons), the total digester capacity is determined by multiplying the capacity of each digester by the fraction of days it was on-line each year and then summing the capacities to determine the total annual capacity. Capacity will vary from year to year depending on how many digesters were in service and whether one or two of the old digesters are in use. The total digester capacity for each year is presented in Table 4-5.

Table 4-5 – Annual Average Digester Capacity

Year Capacity (gallons)

Capacity (cubic ft.)

2001 6863562 917521

2002 8184658 1094125

2003 8002740 1069806

2004 8010929 1070901

2005 8212055 1097787

2006 7996164 1068927

2007 8191781 1095077

The volatile solids loading rate is calculated by dividing the total pounds of volatile solids entering the facility each day by the digester capacity. Volatile solids loading rates for SHDF are given in Table 4-6. In previous master plan documents, the volatile solids loading rate has been calculated for the month of maximum flow in a given year. However, there is a large amount of variability in the measurement of volatile solids. It is logical to assume that the maximum volatile solids loading rate would occur with maximum flow rates into the facility. This is not always the case, and is due to the inherent variability in the measurement of volatile solids in sludge. In 2006, the volatile solids loading rate for maximum monthly flow was lower than the annual average loading rate. For planning purposes, it is good to track both annual and maximum monthly flow volatile solids loading rates.

Table 4-6 – Volatile Solids Loading Rates to Digesters

Year Average Number of Digesters On-Line

Month of Maximum

Flow

Volatile Solids Loading rate at Max. Monthly Flow (lbs/d/ft3)

Volatile Solids Loading rate

at Annual Avg. Flow (lbs/d/ft3)

Difference Between Maximum Month Flow and Annual

Average Flow

2001 4 May 0.0779 0.0746 4.2%

2002 5 February 0.0636 0.0601 5.6%

2003 5 December 0.0643 0.0623 3.2%

2004 5 June 0.0702 0.0646 8.0%

2005 5 March 0.0607 0.0602 0.8%

2006 5 December 0.0623 0.0633 -1.7%

2007 5 June 0.0638 0.0597 6.4%


PAGE 4-8

DRAFT – Dec. 31, 2008

The data in Table 4-6 has been plotted in Figure 4-4. The drop in the loading rate between 2001 and 2002 is explained by an additional digester being put into service in 2002. This increased the digester capacity. The loading rate to the digester complex has remained fairly constant during the period from 2002 to 2007. This is a bit surprising given the population increase that has occurred over this time period.

0.0000

0.0100

0.0200

0.0300

0.0400

0.0500

0.0600

0.0700

0.0800

0.0900

2001 2002 2003 2004 2005 2006 2007

Year

Vola

tile

Solid

s Load

ing R

ate

(lbs/

d/ft3

)

Annual Average Volatile Solids Loading

Volatile Solids Loading at Max. Monthly Flow

Figure 4-4 – Volatile Solids Loading Rate to Digesters

The digesters were designed with a very conservative volatile solids loading rate of 0.07 lbs/(ft3·d). From 2002 to 2007 the digesters have been loaded at a rate less than the design value. The typical design loading rate for digesters is 0.1 to 0.16 lbs/(ft3·d).2 The digesters can be loaded at a significantly higher rate and still would be expected to perform well. However, the sludge would have to be thickened prior to entering the digesters to achieve the higher loading rate. Thickening of influent sludge is discussed later in this section.

The performance of the digesters is measured by the amount of volatile solids that are destroyed. Table 4-7 presents the monthly average reduction of volatile solids at maximum monthly flow and annual average volatile solids reduction achieved by the digesters. The data in Table 4-6 shows more clearly the variation in measuring volatile solids reduction. In three of the years the volatile solids reduction at maximum monthly flow are lower than the annual average. To show the variability of the volatile solids reduction measurement data, Figure 4-5 plots TVS reduction in Digester 8 for data gathered from 2001 to 2007 (Note: The same pattern appears in the plots for all the digesters). The volatile solids reduction ranges from 20% to 75%, but the average is

2 Shun Dar Lin, 2001. Water and Wastewater Calculations Manual, New York: McGraw-Hill, p. 762.


PAGE 4-9

DRAFT – Dec. 31, 2008

approximately 50%. Because of this variability in the volatile solids reduction data, again, from a planning perspective it makes sense to look at both annual and maximum monthly flow reductions of volatile solids.

Table 4-7 – Volatile Solids Reduction in Digesters

Year Month of Maximum

Flow

Monthly Average Reduction of TVS*

in Digesters at Max. Monthly Flow

(%)

Annual Average Reduction of TVS*

in Digesters (%)

Difference Between Max. Month Flow

and Annual Average Flow

2001 May 48.1 50.1 -4.1%

2002 February 50.1 51.9 -3.6%

2003 December 53.7 52.2 2.9%

2004 June 50.4 51.5 -2.1%

2005 March 57.6 52.5 8.8%

2006 December 56.3 52.0 7.7%

2007 June 54.0 53.8 0.3% *TVS – Total Volatile Solids

Total Volatile Solids Reduction in Digester 8

0

10

20

30

40

50

60

70

80

90

100

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08

Sample Date

To

tal V

ola

tile

So

lids

Re

du

cti

on

(%

)

Digester 8 - TVS Reduction %

Linear (Digester 8 - TVS Reduction %)

Figure 4-5 – Reduction of Total Volatile Solids in Digester 8 (2001-Oct. 2008)

The data in Table 4-7 has been plotted in Figure 4-6 and the variation between the monthly averages at maximum flow rates, and the annual averages are quite pronounced in some years. For this variable in particular, the annual average is a more reliable depiction of the data.


PAGE 4-10

DRAFT – Dec. 31, 2008

Also of note in Figure 4-6 is the gently increasing trend in overall volatile solids destruction. This correlates well with the gently decreasing trend that shows up in the volatile solids loading rate to the FSBs shown in Figure 4-7. It makes sense that as more volatile solids are destroyed in the digesters, that the loading rate to the FSBs shows a corresponding slight decrease.

20.00

25.00

30.00

35.00

40.00

45.00

50.00

55.00

60.00

2001 2002 2003 2004 2005 2006 2007

Year

Tota

l V

ola

tile

Solids

Red

uct

ion (%

)

Annual Average TVS % Reduction

Monthly Avg TVS % Reduction at Max Flow

Figure 4-6 – Annual Average Volatile Solids Reduction in Digesters

Volatile solids reduction is measured on a frequent basis throughout the year for each of the digesters that are in service. Table 4-8 presents the annual average reduction of total volatile solids for each of the digesters. Digesters #1 and #2 consistently achieve a higher destruction of volatile solids than Digesters #5 though #8.

Table 4-8 – Volatile Solids Reduction in Individual Digesters

Year Digester (VS Reduction in %)

#1 #2 #5 #6 #7 #8

2001 57.73 59.53 49.62 50.98 48.63 49.46

2002 56.46 55.40 49.13 49.29 49.68 -----**

2003 57.15 57.48 49.42 48.20 51.30 47.02

2004 55.68 55.56 48.10 49.61 49.88 49.75

2005 55.88 55.22 49.85 52.68 51.37 51.47

2006 57.07 56.88 48.41 51.99 49.45 48.81

2007 58.58 58.77 52.41 52.91 51.84 51.17

Average 56.94 56.98 49.56 50.81 50.31 49.61

** Digester 8 was not on-line during 2002


PAGE 4-11

DRAFT – Dec. 31, 2008

Previous evaluations of the need for future digester capacity have based flows on population growth. However, in the last six years, flows at LVSWWTF have not trended with population growth. The same trend has been observed for flows entering SHDF. Year to date flows for 2008 indicate that flows in 2008 will be a little lower than 2007. With limited growth occurring, flows in 2009 are likely to be similar to 2008. In Table 4-9 future flows are listed. The increase in flow rate is based on the increase in flows that occurred in 2003 and 2004 (see Figure 4-2). The average increase in flows during these two years was approximately 16,000 gallons per year. In Table 4-9 it has been assumed that one old digester and four new digesters are in service 97% of the time (based on the past five year average). No flow increases have been assumed for 2007, 2008 and 2009. Flow increases by 16,000 gallons per year after 2009. The minimum detention time required to have Class B quality digested sludge is 15 days. SHDF does not want to operate on an average detention time less than 18 days to provide a buffer for compliance with permit requirements. With these assumptions, Table 4-9 indicates that a sixth digester will need to be placed in service in 2018 because this is the year in which the average detention time drops below 18 days.

Table 4-9 – Future Digester Capacity Needs

Year Flow Detention Time (4 New + 1 Old

Digester) 2007 322400 25.9 2008 322400 25.9 2009 322400 25.9 2010 338400 24.7 2011 354400 23.5 2012 370400 22.5 2013 386400 21.6 2014 402400 20.7 2015 418400 19.9 2016 434400 19.2 2017 450400 18.5 2018 466400 17.9 2019 482400 17.3

Flows can be projected out further to estimate a theoretical date when seven digesters will be on-line, leaving one digester to rotate for maintenance. When the eighth digester is needed, thickening of the influent sludge would need to be undertaken. Using the projected flow assumptions in Table 4-9, thickening of influent sludge is not needed until the year 2027 (based on detention times in 4 old digesters and 3 new digesters).

4.2.3.1. Digester Covers and Rehabilitation The old digesters’ covers are aging and in need of replacement. In addition, parts have been taken from Digester #4 and used to keep Digesters #1 and #2 functioning. Digester #4 cannot be put into service. Digester #3 has been serviced and may perform for a limited time, but this has not been verified. Digester #3 provides back-up capacity, but is not currently in the normal rotation.


PAGE 4-12

DRAFT – Dec. 31, 2008

Rehabilitation of Digesters #1 - #4 will involve replacing the covers and replacing the mixing systems and making other upgrades. The new covers will be fixed and this will increase the capacity of the old digesters because the new covers will span the top of the digesters, whereas the old covers float on the sludge below the top of the walls.

Design work is planned to begin in late 2009 and continue in 2010. The digester upgrades will be constructed in 2011 and 2012. While the existing digesters at SHDF can handle the hydraulic loading for quite a few more years, there is a lot of uncertainty surrounding the toll that harsh operating conditions have taken on Digesters #1 and #2. How many more years they can operate without a major overhaul is uncertain. However, there is consensus that they can operate until digester upgrades occur in 2011 and 2012.

4.2.3.2. Struvite Formation Anaerobic sludge digestion releases ammonium, magnesium and phosphate, which can form struvite in digesters. The chemical formula for struvite is MgNH4PO4·6H2O. Struvite can precipitate in piping systems, particularly where flow is disturbed (like at elbows). Over time the struvite deposits in the piping can restrict flows. Struvite crystals can also settle out of the sludge in the digesters and accumulate on the floor of the digester. Both of these problems have occurred in the digesters at SHDF.

Currently, iron salts (ferric chloride) are being added to influent sludge to decrease the formation of struvite. Some reduction of struvite formation has been observed, but the problem has not been fully resolved.

Extensive research has been conducted on removing struvite ahead of the digesters to be used as fertilizer. As the research and technology matures, this will be a good option to investigate.

4.2.4. Facultative Sludge Basins (FSBs) The purpose of the FSBs is to store, stabilize, and reduce the volume of solids coming from the digesters prior to ultimate disposal in the dedicated land disposal area. The FSBs are long-term storage ponds that contain sludge solids for an average of three to five years before the harvested sludge is removed and land applied. The FSBs have a liquid depth of 15 feet with a surface area of 5 acres each (45 acres in total). Digested sludge is fed to the basins 24 hours per day, 7 days per week. FSBs are operated in parallel, except for one FSB that is offline for dredging to allow solids to be removed from the FSB. The main functions of the FSBs are:

Achieve substantial volatile solids reduction by long-term stabilization of solids. Destroy maximum amount of solids so that less solids are dredged and disposed

to the DLD areas. Provide storage, particularly during months with high precipitation rates when

DLD operations are limited. Promote solids breakdowns by aerobic and anaerobic bacteria Provide pathogen reduction. Thicken sludge to minimize liquid injected into DLD sites.

In order to determine the volatile solids loading rates to the FSBs, the volatile solids going into the digesters, and the volatile solids coming out of the digesters are measured. The inert solids pass through the digesters. The volatile solids loading rate


PAGE 4-13

DRAFT – Dec. 31, 2008

to the FSBs is obtained by subtracting the amount of volatile solids destroyed in the digesters from the influent volatile solids. The loading rates for 2001 to 2007 are presented in Table 4-10. The loading rate has units of pounds of volatile solids per 1000 square feet of FSB surface area. Once again, the loading rates at maximum monthly flow are lower and higher than the annual average values. This is again due to the inherent variability in the measurement of volatile solids in sludge. An annual average value appears to be a better parameter to use for planning purposes.

The data in Table 4-10 has been plotted in Figure 4-7. A slight downward trend can be seen in annual average data (aqua blue line on the graph). This is related to the slight upward trend in volatile solids reduction in the digesters (see Figure 4-6). From a planning perspective, it would be expected that the loading rates will eventually increase. But the last six years of data do not exhibit an increasing trend. This makes projecting future loading rates difficult.

Table 4-10 – Volatile Solids Loading Rates to the FSBs

Year Month of Maximum

Flow

Monthly Average Volatile Solids

Loading rate at Max. Monthly Flow (lbs/1000ft2)

Annual Average Volatile Solids Loading rate at

Annual Avg. Flow (lbs/1000 ft2)

Difference Between

Maximum Month Flow and Annual

Average Flow

2001 May 18.9 17.4 8.0%

2002 February 17.6 16.1 8.6%

2003 December 16.3 16.0 1.9%

2004 June 19.9 17.7 11.4%

2005 March 14.4 15.9 -10.8%

2006 December 14.8 17.2 -15.6%

2007 June 16.4 15.5 5.5%

As a first step to estimating future capacity needs for FSBs the following assumptions have been made: 1) The same flow increase assumptions made for the digester capacity evaluation will be used for the FSBs; 2) The average total dry solids as a percentage of flow will remain the same as recent annual average values; 3) The average volatile solids as a percentage of total solids will remain the same as recent annual average values. The design loading rate for the FSBs is 20 pounds of volatile solids per day per 1000 square feet of FSB surface area. The assumptions about flow rates appear to be very conservative when looking at the history of flow rates in Figure 4-2. Nevertheless, the process of projecting capacity requires assumptions to be made. Table 4-11 presents future loading rates for the FSBs assuming that flows linearly increase from 2010 onward by 16,000 gallons per year.


PAGE 4-14

DRAFT – Dec. 31, 2008

0.0

5.0

10.0

15.0

20.0

25.0

2001 2002 2003 2004 2005 2006 2007

Year

Vo

lati

le S

olid

s L

oad

ing

Rate

(lb

s/d

ay/f

t2)

Monthly Avg TVS Loading Rate at Max. Monthly Flow

Annual Average TVS Loading Rate

Figure 4-7 – Volatile Solids Loading Rate to FSBs

A few more assumptions are made in the calculations in Table 4-11. The annual average of total dry solids as a percent of flow has been slightly increasing over the past five years. Therefore the annual average values from 2006 and 2007 were averaged to represent future years. The total solids are made of inert and volatile solids. The percentage of volatile solids has also been increasing slightly over the past five years, so the annual average values from 2005-2007 were averaged to represent future years. The same assumption was used for the reduction of volatile solids in the digesters with annual average values from 2005-2007 being used.

Based on these assumptions, the data in Table 4-11 conservatively provides an estimate that additional FSB capacity may be needed around 2015 because this is the year when the loading rate to the FSBs exceeds 20 pounds/day/1000 ft2. Due to the conservatism in the assumptions, it is likely that additional FSB capacity will not be needed for several years past 2015.

Another way of looking at FSB capacity comes from examining a mass balance of solids. In Table 4-12 the annual tons of volatile and inert solids that enter the FSBs from the digesters are given. Volatile solids reduction continues to occur in the FSBs over time, and the final value is estimated from the volatile solids measurements that are made on a frequent basis on the sludge that is injected on the DLDs. A mass balance is calculated by subtracting the solids taken out of the FSBs from the solids that “enter” and are stored in the FSBs. The balance starts out negative in 2001 indicating that more solids were injected in the DLDs than came into the FSBs. But from 2003 onward, the mass balance shows that solids began to accumulate in the FSBs.


PAGE 4-15

DRAFT – Dec. 31, 2008

Table 4-11 – Future Capacity of Facultative Sludge Basins (FSBs)

Year Flow (gal)

Total Dry

Solids (%)

Influent Dry

Solids (lbs)

Volatile Solids

in Influent

(%)

Volatile Solids

in Influent

(lbs)

Reduc-tion of VS in

Diges-ters (%)

Volatile Solids

Leaving Digesters

/ Day (lbs)

Loading Rate of FSBs (lbs

VS/d/1000 ft2)

2007 322,400 2.98% 80,116 81.1 64,963 52.77 30,684 15.7

2008 322,400 2.98% 80,116 81.1 64,963 52.77 30,684 15.7

2009 322,400 2.98% 80,116 81.1 64,963 52.77 30,684 15.7

2010 338,400 2.98% 84,092 81.1 68,187 52.77 32,207 16.4

2011 354,400 2.98% 88,068 81.1 71,411 52.77 33,729 17.2

2012 370,400 2.98% 92,044 81.1 74,635 52.77 35,252 18.0

2013 386,400 2.98% 96,020 81.1 77,859 52.77 36,775 18.8

2014 402,400 2.98% 99,996 81.1 81,083 52.77 38,298 19.5

2015 418,400 2.98% 103,972 81.1 84,307 52.77 39,820 20.3

2016 434,400 2.98% 107,948 81.1 87,531 52.77 41,343 21.1

Table 4-12 – Mass Balance of Solids in the FSBs

Year Influent to FSBs

Volatile Solids (Tons)

Inert Solids (Tons)

VS after Storage in FSBs (Tons)

Total Solids

in FSBs (Tons)

Total Solids out of FSBs (Tons)

Balance of

Solids (Tons)

2001 6214 3286 3827 7113 7955 -842 2002 5772 3113 3349 6462 6383 -763 2003 5712 3087 3715 6802 4849 1191 2004 6328 3387 3810 7196 4598 3789 2005 5696 2804 3251 6055 6360 3484 2006 6135 3025 3166 6190 4700 4974 2007 5544 2709 2960 5668 7401 3242

The data in Table 4-12 has been plotted in Figure 4-8. The mass balance indicates that solids built up in the FSBs from 2003 to 2004. From 2005 to 2007 the data shows that injection rates have overall kept up to the loading rates, but significant progress has not yet been made in reducing the volume of solids that have accumulated in the FSBs. Preliminary data from 2008 indicates that some further reduction of the mass balance will occur.


PAGE 4-16

DRAFT – Dec. 31, 2008

-2000

-1000

0

1000

2000

3000

4000

5000

6000

2001 2002 2003 2004 2005 2006 2007

Year

Net

Bal

ance

of Solids

in F

SBs

(Tons)

Figure 4-8 – Mass Balance – Tons of Accumulated Tons of Solids in FSBs

Further monitoring of this mass balance is needed to ensure that solids do not build up in the FSBs due to injection rates falling behind the loading rates. In 2007 work began on construction of DLD #17. Half of DLD #17 was put into service in 2008, but further work is needed to complete the earth work so that the second half of DLD #17 can be used.

4.2.5. Dedicated Land Disposal Units (DLDs) The DLD operations are designed to achieve final land treatment and disposal of biosolids by subsurface soil injection. Subsurface soil injection of FSB-harvested sludge is one of the most cost-effective and environmentally acceptable methods of final land treatment and disposal because the sludge is incorporated directly with the soil, reducing exposure to the atmosphere. The DLD sites were established for the sole purpose of land treatment and disposal to meet the long-term needs of Colorado Springs Utilities and are designed to provide permanent disposal of the sludge removed from the FSBs.

The annual amount of sludge injected in the DLDs from 2001 to 2007 is presented in Table 4-13. The annual volume of sludge injected varies because of climatic conditions. When rainfall is persistent, the fields can be too wet to inject.

From 2001 to 2004, 193.9 acres were used for the DLD system with an additional 15 acres for grit and screening waste disposal from the LVSWWTF. In 2005 the acreage of the western DLDs was reduced to allow a wider buffer area to the western property boundary. In 2006 a new DLD was opened that partially offset the loss of DLD area in 2005. This is why the acreage in use decreased in 2006. A total of 190.8 acres of the Clear Spring Ranch site was used for the DLD system in 2007. Work began on another new DLD in 2007 (DLD #17). Approximately half of it has been completed and this portion of the new DLD was put into service at the start of 2008.


PAGE 4-17

DRAFT – Dec. 31, 2008

The average dry tons of sludge applied per acre per year from 2001 to 2007 was 31 tons. Brown and Caldwell estimated the design capacity of the DLDs to be 127 dry tons/acre/year.3 According to this method of estimating capacity, the DLDs have been loaded well below the design capacity. Part of the reason for this is that climatic conditions do not allow sludge to be injected 365 days a year due to wet weather and frozen ground conditions.

Table 4-13 – Annual Amounts of Sludge Injected on DLDs

Year Gallons Injected

Tons Dry Sludge Applied

Approximate Acres In Use

Dry Tons per Acre

2001 35,893,700 7955 193.9 41

2002 50,892,087 6383 193.9 33

2003 29,370,600 4849 193.9 25

2004 27,875,000 4598 193.9 24

2005 40,172,750 6360 193.9 33

2006 28,545,807 4700 190.8 25

2007 45,334,568 7401 190.8 39

Average 36,869,216 6035 193 31

An exact method for determining when future DLD capacity will be needed does not exist. In large measure it depends on the weather. During favorable years, injection rates can catch up to the solids loading rate in the FSBs. During bad weather years, injection operations fall behind. Most likely the best method for determining the need for additional DLD capacity comes from the mass balance of solids in the FSBs. When injection rates fall behind the loading rates in the FSBs, the need for additional injection capacity arise. Currently, the injection rate appears to be keeping up with the loading rate, but in order to reduce the volume of solids that accumulated between 2002 and 2004, the injection rates will need to be increased.

Work on the expansion of DLD #17 took place in 2007. Approximately half the DLD was completed and that portion was put into service in 2008. Approximately 40% of the earthwork to complete the second half of DLD #17 was done in 2007. Funds were frozen in 2008, not allowing the DLD to be completed. It is recommended that DLD #17 be completed in 2009 to help reduce the solids that have accumulated in the FSBs.

When biosolids start to gum up the soil matrix and make injection of additional biosolids difficult, the field can be ripped by large equipment to turn over the soil from a deeper level. Some of the older DLDs have been ripped and this has helped restore their assimilative capacity.

3 Brown and Caldwell, Clear Spring Ranch Solids Handling Facility Masterplan, Dec. 2003, p. 3-5. Capacity based on 3 injectors, and 25 loads/day at 6 percent dry solids concentration.


PAGE 4-18

DRAFT – Dec. 31, 2008

4.2.6. Supernatant Handling System The supernatant is the water that comes from the digesters after the solids settle in the FSBs. The supernatant from the FSBs flows by gravity to two supernatant storage lagoons on the site. The lagoons are non-discharging to surface streams and act as evaporation ponds. The total surface area of the FSBs and supernatant lagoons is given in Table 4-14.

Table 4-14 – Area of FSBs and Lagoons

Pond Area (acres)

FSBs 45

Lagoon No. 1 13

Lagoon No. 2 23

Total 81

A simple water balance can be conducted to assess the capacity of the lagoons and FSBs to evaporate the supernatant from the FSBs. The first step is to determine an average rainfall value for Clear Spring Ranch. A report by Lincoln and Devore in 1977 had an average annual rainfall value of 14 inches at the Clear Spring Ranch4. CH2M Hill in 1998 estimated the average annual rainfall to be 16 inches5. Table 4-15 presents the rainfall at the Nixon Power Plant’s Base Weather Station for a 10 year period from 1995 to 2004. The Nixon Power Plant is located just to the north of the SHDF.

Table 4-15 – Annual Rainfall at Nixon Power Plant – Base Weather Station

Year Rainfall (inches)

1995 17.3

1996 13.3

1997 18.2

1998 15.8

1999 20.3

2000 9.4

2001 9.7

2002 5.0

2003 11.2

2004 15.1

Average 13.5

4 Lincoln & Devore, Proposed Sewage Sludge Disposal Site, Hanna Ranch, El Paso County, Colorado, 1977. 5 CH2M Hill, Supernatant Management Plan and Zero Discharge Treatment Evaluation: Hanna Ranch Facility, October 1998.


PAGE 4-19

DRAFT – Dec. 31, 2008

The 10-year annual rainfall average in Table 4-15 is 13.5 inches. However, if the drought year of 2002 is excluded, then the average increases to 14.5 inches. CH2M Hill’s average annual rainfall value of 16 inches is probably a good value to use as it is more conservative.

CH2M Hill estimated the average annual evaporation rate from the various ponds at the Nixon Power Plant to be 44 inches6. A common figure in hydrology textbooks presents mean annual lake evaporation rates in the United States7. The Colorado Springs area lies between the lines representing 44 and 46 inches of evaporation. So 44 inches of evaporation is a reasonable number to use for the evaporation rate of water at Clear Spring Ranch.

The results of a water balance analysis are presented in Table 4-16. The annual flow rate assumes an increase of 16,000 gallons per day from 2010 onward (as was used for the capacity analysis for the digesters and FSBs). From the annual influent flow, the gallons of sludge injected in the DLDs on an annual basis needs to be subtracted. The annual volume of sludge injected varies from year to year and is correlated with rainfall. When wet weather persists, the DLDs are too wet to inject sludge. The average of injected sludge volumes from 2001 to 2007 is 36,869,216 gallons. It is assumed that this average value will be representative of future operations. The influent flow to the FSBs and Lagoons is calculated in inches/year and added to the annual average rainfall rate. These values are subtracted from the evaporation rate to determine the excess capacity of the ponds. The excess capacity value turns negative in the year 2023 indicating the year when water will begin to accumulate in the lagoons. At this point action can be taken to increase the evaporation rate from the lagoons or implement another water reduction alternative. The linear increase of the influent flow is quite conservative; therefore, in all likelihood, action will not need to be taken for several years beyond 2023. The fact that the last seven years have had below average rainfall in Colorado Springs also points to a date later than 2023 for capacity of the FSBs and Supernatant Lagoons to be a cause for concern.

Table 4-16 – Capacity Analysis of Supernatant Lagoons

Year Annual Flow (gal)

Annual Gallons Injected

Net Flow to FSBs and

Lagoons (ft3)

Loading to FSBs &

Lagoons (in/year)

Annual Average Rainfall (in/year)

Evapora-tion

(in/yr)

Excess Capa-city

(in/yr)

2007 117,676,000 36,869,216 604,515,551 14.3 16 44 13.7

2008 117,676,000 36,869,216 604,515,551 14.3 16 44 13.7

2009 117,676,000 36,869,216 604,515,551 14.3 16 44 13.7

2010 123,516,000 36,869,216 648,204,591 15.3 16 44 12.7

2011 129,356,000 36,869,216 691,893,631 16.3 16 44 11.7

2012 135,196,000 36,869,216 735,582,671 17.4 16 44 10.6

2013 141,036,000 36,869,216 779,271,711 18.4 16 44 9.6

6 CH2M Hill, Supernatant Management Plan and Zero Discharge Treatment Evaluation: Hanna Ranch Facility, October 1998. 7 Victor Miguel Ponce, Engineering Hydrology, (Prentice-Hall, Inc.: New Jersey), p. 40-41.


PAGE 4-20

DRAFT – Dec. 31, 2008

Year Annual Flow (gal)

Annual Gallons Injected

Net Flow to FSBs and

Lagoons (ft3)

Loading to FSBs &

Lagoons (in/year)

Annual Average Rainfall (in/year)

Evapora-tion

(in/yr)

Excess Capa-city

(in/yr)

2014 146,876,000 36,869,216 822,960,751 19.4 16 44 8.6

2015 152,716,000 36,869,216 866,649,791 20.5 16 44 7.5

2016 158,556,000 36,869,216 910,338,831 21.5 16 44 6.5

2017 164,396,000 36,869,216 954,027,871 22.5 16 44 5.5

2018 170,236,000 36,869,216 997,716,911 23.6 16 44 4.4

2019 176,076,000 36,869,216 1,041,405,951 24.6 16 44 3.4

2020 181,916,000 36,869,216 1,085,094,991 25.6 16 44 2.4

2021 187,756,000 36,869,216 1,128,784,031 26.7 16 44 1.3

2022 193,596,000 36,869,216 1,172,473,071 27.7 16 44 0.3

2023 199,436,000 36,869,216 1,216,162,111 28.7 16 44 -0.7

2024 205,276,000 36,869,216 1,259,851,151 29.8 16 44 -1.8

2025 211,116,000 36,869,216 1,303,540,191 30.8 16 44 -2.8

4.3. Regulatory Evaluation

The regulatory evaluation for SHDF looks at air quality requirements, federal regulations that apply to biosolids operations, and State regulations for groundwater, impoundments and financial assurance.

4.3.1. Air Quality Requirements Because the SHDF is co-located with the Nixon Power Plant, the CDPHE has determined that the sources of air pollution at Clear Spring Ranch constitute a “major source.” Because of this the SHDF operates under a Title V Air Permit.

Some capital projects may require air permit modifications if they cause changes to air emissions. Coordination with the Environmental Services Department is necessary when capital projects with this potential are planned.

4.3.2. Federal Regulations Federal regulations (40 CFR - Part 503) address disposal of sewage sludge. An operating permit is issued by the EPA and contains conditions for operation that are consistent with the 503 regulations. Facilities apply to renew their permit every five years, and the EPA sends confirmation to the facility that their permit has been renewed.

4.3.2.1. Class B Requirements In order for sewage sludge to be surface disposed, it must meet the requirements to be Class B sludge. Several ways of qualifying sludge as Class B are listed in the permit. The SHDF achieves Class B biosolids by anaerobically digesting the sludge in digesters with a mean cell residence time of more than 15 days with the sludge held at a temperature between 35 and 55ºC.


PAGE 4-21

DRAFT – Dec. 31, 2008

4.3.2.2. Vector Attraction Reduction Limitations for Surface Disposal For surface disposal of sewage sludge, one out of nine alternatives has to be chosen to comply with for vector attraction reduction. The alternative used at SHDF requires the mass of volatile solids in the sewage sludge to be reduced by a minimum of 38 percent prior to surface disposal. The annual average volatile solids reduction from 2001 to 2007 is presented in Table 4-17. The seven year average is 80.1% volatile solids reduction. Approximately 52% of the volatile solids reduction occurs in the digesters with the balance of the reduction taking place in the FSBs. The 38% minimum requirement is consistently exceeded by a large amount at SHDF.

Table 4-17 – Annual Average Total Volatile Solids Reduction at SHDF

Year Annual Avg TVS Reduction (%)

2001 79.2

2002 79.4

2003 79.8

2004 79.1

2005 81.1

2006 80.5

2007 81.5

Average 80.1

4.3.2.3. Metals Concentrations in Biosolids Biosolids regulations vary depending on the method used for biosolids disposal. For example if biosolids are being applied to farmer’s fields, the land application regulations are very different from the type of operation at Clear Spring Ranch. At Clear Spring Ranch, sewage sludge is disposed of through surface disposal in sewage sludge units, which are called dedicated land disposal units (DLDs).8

Metals in sewage sludge are of concern and the operating permits for biosolids operations address how metals in sewage sludge are to be measured and establishes maximum concentrations that are allowed. An individual permit was in effect for SHDF from 1995 to 1999. This permit had maximum metals concentrations established for arsenic, chromium and nickel. Maximum concentrations are presented in Table 4-18.

8 The Clear Spring Ranch Solids Handling & Disposal Masterplan prepared by Brown & Caldwell in 2003 has incorporated some land application requirements and applied them to operations at SHDF. These land application requirements in the 2003 Masterplan are not correct for the solids disposal operation at SHDF.


PAGE 4-22

DRAFT – Dec. 31, 2008

Table 4-18 –Maximum Concentration of Metals in ’95-’99 Permit

Pollutant Daily Maximum Conc. (mg/Kg)

Total Arsenic 36

Total Chromium 413

Total Nickel 263

The EPA developed new language for a general permit for biosolids operations in 2002. However, they did not actually renew the permit for SHDF until 2007. This means that SHDF was operating under the 1995-1999 permit all the way from 1995 to 2007. This is important for understanding how disposal operations have been conducted during this timeframe.

In the general permit that was issued to the SHDF in 2007, there are new requirements for metals concentrations in the sludge. If the distance from the property boundary to the edge of the closest DLD is 150 meters (492.1 ft) or greater, then there are three metals that have a daily maximum concentration that cannot be exceeded. These metals and their concentration thresholds are listed in Table 4-19.

Table 4-19 –Maximum Concentration of Metals

Pollutant Daily Maximum Conc. (mg/Kg)

Total Arsenic 73

Total Chromium 600

Total Nickel 420

Table 4-20 presents the maximum allowable concentrations of metals when the distance between the DLDs and the property line is less than 150 meters (492.1 feet). The requirements for separation distances between the DLDs and the property line became effective in 2007.

Table 4-20 – Maximum Conc. of Metals when DLDs < 150 Meters

Pollutant Concentration (mg/Kg) Distance from Unit Boundary to Property Line – Meters (Feet) Arsenic Chromium Nickel

0 to less than 25 (0-82.0 ft) 30 200 210

25 to less than 50 (82.0-164.1 ft) 34 220 240

50 to less than 75 (164.1-246.1 ft) 39 260 270

75 to less than 100 (246.1-328.1 ft) 46 300 320

100 to less than 125 (328.1-410.1 ft) 53 360 390

125 to less than 150 (410.1-492.1) 62 450 420


PAGE 4-23

DRAFT – Dec. 31, 2008

Table 4-21 presents monthly monitoring data for arsenic, chromium, and nickel from 2001 to 2007. Annual averages and the maximum values for the three metals are presented. Comparison of the data in Table 4-21 to the maximum allowable concentrations in Table 4-18 shows that the facility operated in full compliance with the maximum concentrations in the 1995-1999 permit that was in effect from 1995 to 2007.

In early 2006 some of the laboratory data for arsenic showed elevated levels. But when the samples were re-run, it was confirmed that the elevated levels came from a matrix interference that was not accounted for in the initial lab work. While this issue was being sorted out, a decision was made to implement a 75 meter offset between the property boundary and the four western DLDs. This offset has been maintained from 2006 to 2008 and has reduced the full acreage available for injection. Construction of several new DLDs has been undertaken to address the reduced injection acreage, but the acreage has not been fully replaced as of 2008.

Examination of the data in Table 4-21 shows that only arsenic is of concern when historical monthly maximum concentrations of the three metals are compared to the maximum concentrations in Table 4-20. The annual average and monthly maximum concentrations that were measured in the biosolids from 2001 to 2003 were well below the new 2007 maximum concentrations in Table 4-18. If the 2007 requirement had been in effect at the time, a 25-50 meter offset from the property boundary would have needed to have been followed for some of the months in 2004 and 2005. However, the 2006, 2007, and year-to-date data for 2008 show that no offset distance would be needed. Because arsenic concentrations have dropped significantly in 2007 and 2008, Springs Utilities should re-open some of the closed portions of the western DLDs. Injection in this additional DLD acreage will help decrease the solids build-up that has occurred in the FSBs. To allow for some conservatism in operations, and due to the fact that arsenic concentrations can jump from month to month, it would be good to keep a 25 meter setback from the property boundary in place. This would still allow two-thirds of the previously restricted acreage to be put back into service.

Table 4-21 – Metals Sample Data from Biosolids

Arsenic (mg/Kg) Chromium (mg/Kg) Nickel (mg/Kg) Year

Annual Avg.

Monthly Max.

Annual Avg.

Monthly Max.

Annual Avg.

Monthly Max.

2001 3.8 8.6 76 148 45 88

2002 3.5 5.3 65 97 40 65

2003 5.4 18 62 126 38 21

2004 17.2 32.7 63 127 36 89

2005 22.3 32.9 43 49 57 151

2006 19.6 28.9 48 84 41 106

2007 10.3 16.6 37 56 24 34

Jan-Oct, 2008 7.4 16.0 40 72 26 44


PAGE 4-24

DRAFT – Dec. 31, 2008

4.3.3. Monitoring Requirements The frequency for monitoring for metals in the disposal sludge depends on the dry tons of sludge disposed of in a year. Because SHDF disposes of more than 15,000 dry metric tons per year, the facility is required to monitor for metals once a month (12 times per year).

The facility is required under the biosolids permit to have a ground water monitoring plan to determine if material leached from the DLDs is increasing the concentration of nitrates in the groundwater and to provide a method of determining if the placement of sewage sludge in the DLDs should be terminated. The plan needs to include, at a minimum, the location of all monitoring wells and a schedule for sampling and analysis for nitrate. The SHDF has a groundwater monitoring plan that calls for quarterly sampling of upgradient and downgradient wells for nitrate and other parameters. Annual groundwater reports summarizing the results are submitted to the Colorado Department of Public Health & Environment (CDPHE).

4.3.4. State and Local Regulations

4.3.4.1. Groundwater The CDPHE issues groundwater monitoring regulations for the SHDF. Groundwater monitoring plans are reviewed and approved by the CDPHE. The Environmental Services Department of Springs Utilities collects upgradient and downgradient well samples quarterly. A statistical software program is used to analyze the data to determine if the downgradient concentrations are higher than upgradient concentrations at a statistically significant level. The SHDF has operated in compliance with the groundwater monitoring regulations.

Two years ago the CDPHE requested a change in the statistical method used to compare upgradient and downgradient concentration. The statistical method requested by the CDPHE has reduced the margin of compliance for nitrates in groundwater at the facility and is being monitored closely.

4.3.4.2. Impoundments Mid 2008, the CPDHE proposed to update the regulations for solid waste impoundments. The new requirements for impoundments will have large impacts on solid waste facilities. The regulated community is working with the CPDHE in a stakeholder process to provide input on the revised regulations.

For now, facilities are submitting data to the CDPHE on their impoundments. This information includes impoundment construction information, geological information, and characterization data of the waste held in the impoundments.

The full impact of the regulations is not known at this time. But one possibility is that the supernatant lagoons and the pond behind the stormwater retention dam may need to have liners that meet a 1 x 10-7 cm/s seepage rate. Additional groundwater monitoring wells may also need to be installed and analyzed on a quarterly basis. Leak detection systems may also need to be installed.

Solid waste impoundments that previously had waivers, or were thought to be covered under water quality regulations may now need to be retrofitted to meet the proposed regulation. The proposed regulation is scheduled to be re-issued for comment in


PAGE 4-25

DRAFT – Dec. 31, 2008

November of 2009. The updated regulation is expected to be promulgated in early 2010. Facilities may be given two years to upgrade their impoundments to meet the new regulations. Due to the proposed changes to the impoundment regulations, an alternatives analysis will need to be conducted in 2009.

4.3.4.3. Financial Assurance Every five years financial assurance documents have to be updated and submitted to the CPDHE. The financial assurance process ensures that the operator of a solid waste facility has the financial means to close the facility at the end of active operations. A closure plan is submitted along with cost estimates for closure activities. Spring Utilities and the City of Colorado Springs submit a combined financial assurance document for all solid waste facilities operated by the Springs Utilities and the City. The basic mechanism to show that the City has the financial means to close the facilities is by demonstrating that the total closure costs are a small percentage of the annual revenue stream of Springs Utilities and the City. Annual updates applying inflation to the closure costs are submitted to the State with the continued demonstration that the closure costs are a small percentage of total revenue.

4.4. Alternatives Development

Capital improvements that need to be made in the next 10 years at the SHDF, include replacement of digester covers on four of the old digesters and dealing with impacts from new impoundment regulations being developed by the State. Alternative analyses will be conducted for both of these projects in 2009. An alternatives study for utilization of digester gas was completed in 2006 and is discussed below.

4.4.1. Digester Covers An alternatives analysis will be conducted in 2009 for the types of covers that need to be installed if the four old digesters are to remain in service for the next 15 to 20 years. The current floating covers on the four old digesters have corroded over the time they have been in service and need to be replaced. Other upgrades are also needed to ensure their long-term operation. Options for covers include fixed aluminum covers or fixed concrete covers. Installing fixed covers increases the working capacity of the digesters because the current floating covers sit below the top of the digester walls. The fixed covers will be placed at the top of the digester walls allowing more sludge to be treated.

4.4.2. Impacts from New Impoundment Regulations New solid waste impoundment regulations are expected to be promulgated in 2010. The impacts on SHDF from the new regulations are not fully known yet, but in 2009, an alternatives analysis will be conducted to evaluate several alternatives against possible impacts to the existing operations at SHDF. The 2009 impoundment alternatives analysis will help develop budgetary numbers for impacts to existing operations and for the alternatives developed.

Alternatives may include: 1) a small treatment plant to handle supernatant flows, sludge thickening, and composting of the biosolids; 2) drying the sludge and burning it at a power plant; 3) upgrading impoundments and continuing existing operations. Other alternatives may be evaluated as well. Money has not yet been budgeted for the


PAGE 4-26

DRAFT – Dec. 31, 2008

impacts from the new solid waste impoundment regulations for any of Springs Utilities facilities because they are still in the development stage.

4.4.3. Digester Gas – Energy Recovery Methane constitutes approximately 60-65% of digester gas and is a valuable resource that has been used to heat the digesters. However, digester gas also contains hydrogen sulfide gas, water vapor and siloxanes that all have to be removed from the gas stream before it can be burned in a generator. Hydrogen sulfide gas turns into an acid when it comes in contact with water and will corrode gas turbines if it is not removed from the gas stream. Siloxanes are polymers that are used in commercial, personal care, industrial, medical and even food products. The heating that occurs in the digesters causes siloxanes to volatize into gaseous form and when burned, the siloxanes form a sand-like material that is deposited in the combustion chambers. To protect the combustion equipment, siloxanes must be removed from the digester gas before combustion.

Digester gas utilization technologies have steadily improved over the years. In 2006, Springs Utilities contracted Black & Veatch to conduct a thorough evaluation of a biogas system that generates electricity from gas that is currently flared and provide a conceptual design.9

Using 2006 dollars, Black & Veatch estimated that the levelized cost was $100/MWh of power produced from digester gas. With recent inflation rates rising, this cost would be expected to be significantly higher in 2008 dollars. The B&V estimate included systems to clean up and dry the gas and then generate electricity from it. The annual O&M cost was estimated to be $470,000 per year. Wind power can be installed for approximately $70-90/MWh (includes transmission costs). It does not appear at this time that energy recovery from excess digester gas is viable.

However, energy recovery from excess digester gas is a goal that makes a lot of sense to pursue. Innovation is continuing to occur in finding more cost effective ways to clean up the digester gas and use the energy. For instance a recent article in Rumbles described an 8 mgd plant that was installing a demonstration project to clean up their digester gas and enrich it to produce pipeline grade natural gas.10 This type of operation has been successfully done on large scale systems that have operated for more than six years. The vendor now wants to demonstrate the viability of doing it on a smaller scale with wastewater treatment plants in the 5 to 50 mgd size. The vendor plans to have a small capacity unit designed by mid-2009 and enter into partnerships with municipalities, where the municipality contributes the gas and electrical power with both parties sharing the revenue.

It is ongoing innovations like this that will lead to a viable way to recover energy from the excess digester gas at SHDF. Continued research and evaluation of technologies needs to be ongoing.

9 Black & Veatch, Biogas System Conceptual Design Study, December, 2006. 10 Wayne Ballantyne and Darin Wise, “Ohio Wastewater Treatment Plant Seeks $$$ from their Flared Digester Gas,” Rumbles, RMAWWA/RMWEA, Vol. 48, No. 5, p. 10-14.


PAGE 4-27

DRAFT – Dec. 31, 2008

4.5. Capital Improvements Budget

The capital budget amounts shown in Table 4-22 reflect currently planning for future capital projects for the next 10 years. Capital money has not yet been budgeted for dealing with impoundment requirements that are being developed by the CDPHE. This is because the full impact is not yet known and an alternatives analysis still needs to be conducted.

Table 4-22 – Budgeted Amounts for Capital Projects at SHDF (in millions)

Project 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018

Digester Covers $0.1 $0.41 $3.55 $2.75 $0 $0 $0 $0 $0 $0

FSB Expansion $0 $0 $0 $0 $0.0 $0.36 $3.27 $0 $0 $0

DLD #17 $0.15 $0 $0 $0 $0 $0 $0 $0 $0 $0

Various Small Projects

$0.11 $0 $0 $0.0 $0.04 $0 $0 $0 $0 $0

Total $0.26 $0.41 $3.55 $2.75 $0.04 $0.36 $3.27 $0 $0 $0

WASTEWATER INTEGRATED MASTERPLAN GLOSSARY


5. GLOSSARY

AMMTOX – a computer model that calculates ammonia degradation as a function of time and distance in creeks downstream of wastewater treatment facilities

AWT – Advanced Wastewater Treatment

BLR – Banning Lewis Ranch Development

BSPS – Blended Sludge Pump Station located Las Vegas Street Wastewater Treatment Facility – the pumps that move sludge from LVSWWTF to SHDF

Build-out – refers to the time when development is complete within a sewer drainage basin, all the houses and commercial buildings that are going to be built have been constructed resulting in the maximum flows of wastewater from the basin

CBOD or CBOD5 – Carbonaceous Biochemical Oxygen Demand – a measure of the organic strength of wastewater.

CCTV – Closed Circuit Television

CIP – Capital Improvement Program at Springs Utilities

CIPP – Cured-in-Place Pipe

CDOW – Colorado Division of Wildlife

CDPHE – Colorado Department of Health & Environment – State Agency

CMOM – A proposed Federal Rule for sanitary sewer systems that contains requirements for Capacity, Management, Operations and Maintenance

COC – Compliance Order on Consent – an agreement between the CDPHE and regulated entity that stipulates conditions that must be complied with

Collector – sewer pipes with a diameter from 9 inches to 16 inches to which local collectors (8 inches and smaller) are connected

CSRRP – Collection System Rehabilitation and Replacement Program

CWQCA – Colorado Water Quality Control Act

Diurnal Flow Profile – diurnal means daily, the daily flow profile typically has two peaks, one that occurs in the morning and one that occurs in the evening

DLDs – Dedicated Land Disposal Units – designated fields exclusively used for injection of stabilized sewage sludge

EPA – Environmental Protection Agency

FEMA – Federal Emergency Management Agency

FIMS – Facility Information Management System

Fixed film – a trickling filter provides a very large surface area with plastic media on which a biological mat grows. In fixed film growth systems, aerobic microorganisms



attach and grow on an inert media. Wastewater flows across a slime layer created by the attached microorganisms, which extract soluble organic matter from the wastewater as a source of carbon and energy.

FOG – Fats, Oil and Grease

FSBs – Facultative Sludge Basins at Solids Handling & Disposal Facility

GIDS – Geographic Information System

GWI – Groundwater infiltration

Head/discharge curves for pumps – these curves describe the range of operations for pumps in terms of the flow the pump can deliver (discharge) against elevation and friction (head). The higher the elevation and friction losses, the less flow the pump can deliver, and vice versa.

I/I – Infiltration and inflow

Interceptor - Large diameter sewers (36” and larger) that collect wastewater from local trunk sewers (also called main sewers) and conveys the flow to a wastewater treatment plant.

IT – Information Technology

JDPWRF – J.D. Phillips Water Reclamation Facility

LCERP – Local Collectors Evaluation and Rehabilitation Program

LIDs – Unique identification numbers for each manhole and pipe in the collection system

Local collector – sewer pipes that are 8 inches and smaller in diameter

LVSWWTF – Las Vegas Street Wastewater Facility

MGD or mgd – Million gallons per day

MHERP – Manhole Evaluation and Rehabilitation Program

MWH – Montgomery Watson Harza – a consulting firm

NASSCO - National Association of Sewer Service Companies

O&M – Operation and Maintenance

PACP - Pipeline Assessment and Certification Program

PST – Primary Sedimentation Tank

RDI/I – Rainfall dependent infiltration/inflow

QBD – Quality By Design – a Springs Utilities document system that documents processes and procedures with an aim to improving quality

SHDF – Solids Handling & Disposal Facility

SSCC – Sanitary Sewer Creek Crossing Program

SSEP – Sanitary Sewer Evaluation Program

SSERP – Sanitary Sewer Evaluation and Rehabilitation Program



SSOs – Sanitary sewer overflows

Suspended growth - Suspended growth treatment systems are variations of the activated sludge process in which microorganisms are suspended in an aerated reactor tank by mixing. Oxygen is supplied to oxidize organic carbon and nitrogen compounds.

Trunk Sewer – a sewer pipe with diameter size ranging from 17 inches to 35 inches to which collector sewer pipes (9”-16” diameter) are connected

ULF – Ultra low flush

USACOE – U.S. Army Corps of Engineers

USGS – United States Geologic Survey

UV – Ultra-violet light used in disinfection systems

WWIM – Wastewater Integrated Masterplan

WASTEWATER INTEGRATED MASTERPLAN INDEX


6. INDEX

Ammonia Limits .................3-15, 3-16, 3-17

AMMTOX ......................................3-15, 3-16

anaerobic digesters................... xii, 4-2, 4-3

Anaerobic digesters.................................... 4-4

AWT................. x, 3-1, 3-2, 3-14, 3-19, 3-20

Bioplant ................................... 3-1, 3-2, 3-14

BioWin ...........................................3-10, 3-19

Blended Sludge Pump Station ..............4-3

CBOD .........................3-1, 3-2, 3-3, 3-4, 3-5

CCTV...............2-18, 2-23, 2-24, 2-25, 2-27

CDPHE.. xii, 2-16, 2-17, 2-18, 3-5, 3-15, 3-16, 3-17, 4-21, 4-25, 4-28

CIPP ........................................................2-27

Clear Spring Ranch.. xi, 1-7, 1-11, 3-13, 4-1, 4-17, 4-18, 4-19, 4-20, 4-21, 4-22

CMOM ...........................................2-17, 2-24

COC. 2-16, 2-17, 2-18, 2-19, 2-23, 2-24, 2-29, 2-32

Collection mains ......................................1-2

Cured-in-Place Pipe

CIPP ....................................................2-27

Digester capacity . 4-6, 4-7, 4-8, 4-11, 4-15

Digester Covers .................4-12, 4-26, 4-28

Digester Gas............................................. 4-27

DLDs... xi, xii, 1-11, 4-2, 4-3, 4-16, 4-17, 4-18, 4-20, 4-22, 4-23, 4-24, 4-25

E. coli.......................x, 3-6, 3-12, 3-16, 3-17

EPA............................2-17, 3-15, 3-21, 4-23

Facultative Sludge Basins ...xi, 4-2, 4-3, 4-13, 4-15

Fats, Oil and Grease....................... 2-33, 3-13

Fecal coliforms................. x, 3-6, 3-12, 3-15

FIMS.........................................2-3, 2-4, 2-18

Financial assurance.................... 4-21, 4-26

FOG .......................... 2-33, 2-34, 3-13, 3-18

Force Main ................................ viii, 1-2, 2-4

Force mains ............................................. 1-2

FSBs ...xi, xii, 4-2, 4-3, 4-4, 4-5, 4-10, 4-13, 4-14, 4-15, 4-16, 4-17, 4-18, 4-19, 4-20, 4-22, 4-24

Gravity Main...................................... viii, 1-2

Hydrogen sulfide .............. x, 3-14, 4-6, 4-27

Impoundment...............xii, 4-26, 4-27, 4-28

J.D. Philips Water Reclamation Facility

JDPWRF .............................................. 1-8

JDPWRF ..ix, x, xi, 1-2, 1-4, 1-8, 1-11, 3-1, 3-10, 3-12, 3-20, 3-21, 4-1, 4-3

Las Vegas Street Wastewater Treatment Facility..vii, ix, xi, 1-4, 1-10, 2-8, 3-1, 4-1

LCERPviii, 2-12, 2-16, 2-24, 2-25, 2-27, 2-28, 2-29, 2-31, 2-32

Lift stations . viii, 1-2, 1-4, 2-2, 2-4, 2-16, 2-17, 2-18

Liquid Waste Receiving Station 3-13, 3-18

Local Collectors Evaluation and Rehabilitation Program ...viii, 2-16, 2-24

LVSWWTFix, x, xi, 1-4, 1-5, 1-8, 1-11, 2-8, 3-1, 3-2, 3-3, 3-4, 3-5, 3-6, 3-7, 3-8, 3-9, 3-10, 3-11, 3-12, 3-13, 3-14, 3-15, 3-16, 3-17, 3-18, 3-19, 3-20, 4-1, 4-2, 4-3, 4-4, 4-5, 4-11, 4-17

Metals ... 3-15, 3-17, 3-18, 4-22, 4-23, 4-24

Metals Concentrations in Biosolids .... 4-22

MHERP.................................... ix, 2-16, 2-32

NASSCO ........ 2-21, 2-25, 2-26, 2-27, 2-30

WASTEWATER INTEGRATED MASTERPLAN INDEX


National Association of Sewer Service Companies

NASSCO .................................... 2-21, 5-2

Nixon Power Plant ............4-19, 4-20, 4-21

Precipitation ................................... 2-30, 3-7

Rainfall 2-6, 2-7, 2-8, 2-11, 3-6, 3-7, 3-8, 3-9, 3-10, 4-5, 4-17, 4-19, 4-20, See Precipitation

Sanitary Sewer Creek Crossings Program............................................viii, 2-16, 2-29

Service territory ....................................... 1-6

Service Territory Boundary.................... 1-2

Sewershed ............................. 2-5, 2-6, 2-11

Sewersheds ........................... 2-5, 2-8, 2-12

SHDF . xi, xii, 1-7, 1-8, 1-11, 3-13, 3-18, 4-1, 4-2, 4-3, 4-4, 4-5, 4-6, 4-7, 4-11, 4-12, 4-13, 4-21, 4-22, 4-23, 4-25, 4-26, 4-27, 4-28

Siloxanes ................................................4-27

Sky Flume ......................x, 3-12, 3-14, 3-19

Solids Handling & Disposal Facility

SHDF ............................. xi, 1-7, 1-11, 4-1

Springs Utilities vii, viii, ix, xi, 1-1, 1-2, 1-7, 2-1, 2-2, 2-3, 2-4, 2-11, 2-12, 2-13, 2-16, 2-17, 2-18, 2-19, 2-21, 2-22, 2-25, 2-27, 2-29, 2-30, 2-31, 2-32, 2-33, 2-34, 3-1, 3-5, 3-9, 3-11, 3-17, 4-1, 4-17, 4-24, 4-25, 4-26, 4-27

SSCC................. viii, 2-16, 2-29, 2-32, 2-33

SSERP ... viii, 2-12, 2-16, 2-18, 2-19, 2-23, 2-24, 2-25, 2-28, 2-29, 2-31, 2-32

SSOs . viii, 2-12, 2-16, 2-17, 2-24, 2-25, 2-29

Stoppages .2-12, 2-13, 2-20, 2-28, 2-33, 3-13

Struvite ................................................... 4-13

Supernatant lagoon .xii, 4-2, 4-19, 4-26, 4-27

UV system.......................................... x, 3-12

Volatile solids 4-2, 4-4, 4-5, 4-6, 4-7, 4-8, 4-9, 4-10, 4-11, 4-13, 4-14, 4-15, 4-16, 4-22

Wastewater Basins..................................1-2

Water conservation .................................3-9

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