Environmental Task Force SSSMP Summary, September 18, 2011 Scheduled for City Council Approval September 26, 2017

Sanitary Sewer System Master Plan Summary Points - • City’s sanitary system has very good system performance• Integration of the DCP and other LUCE projections indicates

average sewer flows will increase by approximately 10%through build-out

• Majority of the pipelines meet System Evaluation Criteria• Majority of the manholes meet System Evaluation Criteria• Collection System has adequate capacity to serve future –

with certain exceptions• Hydraulic Model serves as a valuable tool for future analysis.

Additional field data will support validation of CIP projects• The sanitary sewer system has minimal potential capacity

limitations• Integration of SWIP’s 1.2 MGD Water Reclamation Plant will

provide additional downstream capacity relief• City’s Net Zero program will benefit overall system capacity

however individual new development projects should beincluded “as-is” for conservative capacity analysis

• Current conditions: 1% of existing sewers under capacity• Future conditions: 3% of existing sewers under capacity• 5 year CIP developed:

Description Year 1 Year 2 Year 3 Year 4 Year5

Capacity Improvements $2,000,000 $1,200,000 $1,600,000 $2,000,000

Field Review Services $100,000 $80,000

Pipeline Replacements $900,000 $1,800,000 $1,400,000 $2,920,000 $1,000,000

TOTAL ANNUAL CIP $3,000,000 $3,000,000 $3,000,000 $3,000,000 $3,000,000

Attachment 1

Background

The City of City of Santa Monica (the City) contracted with HDR Engineering, Inc. (HDR) to

develop its 2017 Sanitary Sewer System Master Plan (SSSMP). This Master Plan is designed to

serve as a roadmap for the City to proactively manage and maintain adequate capacity of the

local sanitary sewer system. The primary purpose of this planning document was to evaluate the

capacity of the City’s existing sanitary sewer system under current conditions, and plan for the

capacity required by future conditions associated with a number of new development projects in

the City.

The City’s sewer system consists of a combination of gravity sewers, force mains, monitoring

stations and a lift station to help convey sewage to the City of Los Angeles’ (Los Angeles or LA)

Hyperion Wastewater Treatment Plant (HTP). The City’s sanitary sewer facilities include

approximately 152 miles of pipelines, 2,800 maintenance holes, two permanent flow monitoring

and sampling stations and one, 26 million gallons per day (MGD) pumping station, referred to as

the Moss Avenue Pump Station (MAPS). The City’s system is divided into ten primary service

areas or drainage basins, B1 to B10 to collect and convey sewage by gravity towards the ocean

for final collection and discharge to Los Angeles for wastewater treatment and disposal. The

City’s sanitary sewer system is shown on Figure 1.

This 2017 SSSMP was prepared to reflect current growth in the City and anticipated future

developments, and to provide the City with a tool for planning improvements needed for

sanitary sewer collection system infrastructure. These improvements are necessary to

accommodate growth within the City and will be implemented within the City’s Capital

Improvements Program (CIP).

Figure 1. City Sanitary Sewer System

Current and Projected Sewer Flows

To fully understand and plan for the capacity needs of the sanitary sewer system, future flows

estimates need to incorporate the changes in sanitary flows from growth, referred to as dry

weather sewage flow, and the additional water that enters the sewer system from storm-related

events, referred to as wet weather flow. To account for the potential increase and changes in

land use and redevelopment density, the City provided a listing of approximately 55 new

development opportunities that are filed with the Planning Department. These development

projects, including the recently adopted Downtown Community Plan (DCP), and their status in

the development process are depicted graphically on Figure 2.

The additional sanitary sewer flow associated with these development projects are derived by

correlating the applicable sewer discharge factors for the land use types and densities of each

development project. Based on these factors, future average dry weather flows are projected to

increase by approximately 2.1 million gallons per day (MGD), an increase of approximately 14

percent. Approximately half of this increase is projected to occur in the DCP area. A summary of

the average annual existing and future projected flows under dry weather conditions are shown

in Table 2.

Figure 2. City New Development Project Status

Table 2. Sanitary Sewer Flow Projections

Flows

Existing

Conditions

Future

Conditions

Average Flows (MGD) 14.4 16.5

Note: Average annual flows shown herein exclude areas of the City that do not discharge sewage

to City facilities, and the impact of other future flow reducing programs described herein.

It is important to note that the City has adopted a number of activities to continue to support its

sustainability goals and minimize its local footprint. Foremost among these programs is the

recently adopted Water Neutrality Program and the programmatic efforts of a Sustainable

Water Infrastructure Project (SWIP). Each of these programs will affect the projected overall

increase in sewer flows shown in Table ES-2, and are summarized below.

Water Neutrality Program

In May 2017, the Santa Monica City Council adopted a Water Neutrality Ordinance to require

that new development offset water use on site or off site, or alternately, pay the City an in-lieu

fee to fund retrofitting of plumbing fixtures offsite. The ordinance would not allow a new

development to exceed the water use of the existing development on that property. If that

requirement could not be met onsite, the excess water demand would have to be offset by

reducing the water demand (through fixture replacement) at other sites within the City. Given

this water neutrality requirement, much if not all of the projected overall increase in future

sewage flow should be offset through this growth funded plumbing fixture retrofit program.

It should be noted that while this water neutrality program may offset an increase in overall

sewage flows, the program does allow for an increase in flows at any specific site. With this

program provision, some of the large future developments could still have a substantial point

load increase in sewage discharges. To plan for this potential increase associated with these

developments and to assure adequate capacity in the sanitary sewer system collection system

network, the impact of site specific increases have been incorporated in the hydraulic

model. Proceeding in this manner, the impact of new development is conservatively included in

the system capacity assessment to reduce the risk of sanitary sewer overflows throughout the

City and in the Downtown Community Plan area.

SWIP – Water Reclamation Facility (WRF)

The City of Santa Monica Sustainable Water Infrastructure Project (SWIP) is comprised of

three elements which are integrated to provide for treatment and conjunctive reuse of

brackish/saline impaired groundwater, recycled municipal wastewater, and stormwater

runoff. In addition, the SWIP will help improve the water quality in the Santa Monica Bay by

increasing non-point source control. The three elements of the City’s SWIP program are:

SWIP Element 1: Brackish/Saline Impaired Groundwater Reuse,

SWIP Element 2: Recycled Water Production and Conjunctive Reuse, and

SWIP Element 3: EWMP Stormwater Harvesting and Reuse.

It is SWIP Element 2 that has the greatest benefit to the City’s sanitary sewer system as it

will be designed to recycle approximately 1 MGD of its municipal wastewater for local reuse.

The planning and long-term funding of this new underground water reclamation facility

(WRF) is well underway, with the final plant being sited near the Civic Auditorium.

When completed, this WRF will benefit the City’s sanitary sewer system by removing

approximately 1.2 MGD of sewage from the 39-inch/54-inch sewer pipelines near Ocean

Avenue, and return only 0.2 MGD of sludge and brine from the WRF to an 18-inch line near

Pico Blvd. and 3rd Street. The removal of the 1 MGD of flow will provide additional pipeline

capacity from the WRF to the City’s outfall, and reduce the cost of wastewater treatment

and disposal currently charged by the City of Los Angeles. The projected configuration of the

new SWIP WRF is shown in Figure 3.

Figure 3 - SWIP Projected Flow Diversion and Disposal Plan

System Analysis, Findings and Recommendations

An integral element of the Master Plan was the development and deployment of a temporary

flow monitoring program at strategic locations throughout the City. In addition to the City’s

permanent flow meter data, 12 temporary flow meters were installed. This temporary flow

monitoring program was conducted in April 2016, measuring 5-minute intervals throughout the

dry weather flow monitoring period at the 12 locations. Flow meter data collected by the 12

temporary meters were also used along with permanent flow meter data to develop diurnal

patterns, unit generation rates, and calibration data points for the hydraulic model.

Field survey services were also performed to collect elevation information that was required to

develop the City’s updated hydraulic model. As part of the Master Plan, approximately 200

locations were field surveyed for the collection of elevation data for the City’s maintenance

holes and pipe inverts. This information, combined with field survey data obtained in the 2011

study, was used to improve the accuracy of the sewer system hydraulic model.

To support the evaluation of the City’s sanitary sewer system for both existing and build-out

conditions, a hydraulic model was developed. The hydraulic model development activities

included a comprehensive review of the GIS/SCADA/Billing data, sewer flow analysis and

allocation, elevation extraction for the model facilities based on survey data, diurnal pattern

assignments, analysis of dry and wet weather peaking factors and model calibration based on

flow monitoring data.

The calibrated sanitary sewer system hydraulic model was used to perform a comprehensive

capacity analysis of the sewer system under current and build-out conditions. These modeling

simulations determined the adequacy of the system capacity under dry weather and wet

weather conditions, and subsequently identified potential improvements. Capital improvement

projects were identified to support the City in its planning and budgeting processes.

In summary, the analysis found the City’s sanitary sewer system performs exceedingly well and

there are very limited areas where the hydraulic capacity of the existing sewer system may fall

short of the applicable evaluation criteria for both depth of flow in the pipeline or level of flow

surcharging in a sewer maintenance hole. Under existing conditions, approximately 1% of the

system may experience a capacity shortfall. In utilizing the model to simulate future build out

conditions, the City’s sewer system continues to perform well. In fact, under future conditions,

only 3% of the modeled pipelines exceeded the evaluation depth of flow criteria.

During the development of the City’s sanitary sewer system Capital Improvement Program (CIP),

the recommended improvement projects were classified into the following categories, Table 3:

Priority 1: Facilities with model predicted capacity limitations under existing conditions

scenario. Potential Capacity-Related Improvements are provided in Figure 4

Priority 2A: Field verification candidates requiring additional facility information.

Priority 2B: Field verification candidates requiring additional flow information.

Priority 3: Facilities with model predicted capacity limitation under future conditions scenario

Priority 4: Facilities identified by the City as replacement candidates and warrant additional

attention or replacement under the City’s programmatic facility condition

assessment and replacement program.

Figure 4. Summary of Potential Capacity-Related Improvements

Table 3 Potential Capacity-Related Improvement Projects

CIP Priority Total Pipe Length (feet) CIP Year

1 (Existing Conditions Capacity

Projects) 5,800 Year 1

2A (Field Facility Information

Verification 3,000 Year 1, 2

2B (Flow Verification) 4,650 Year 3, 4

3 (Future Capacity Projects) 5,750 Year 5

The recommended capacity improvement-related projects include required capacity expansions

of the existing system to convey future/ultimate flows under design flow conditions. The

resulting capacity improvement projects are prioritized by considering the following factors:

Model-predicted overflows

Model-predicted surcharging

Reported recurring overflows

In addition to the capacity-related facility improvement recommendations, the City maintains an

ongoing asset management program to facilitate the programmatic assessment of facility

condition and replacement. Through this program, the City has identified a number of pipeline

segments that warrant additional attention or are in need of replacement. The location of these

pipelines are shown on Figure 5.

Figure 5. Summary of Condition-Related Improvements

The condition related improvements shown represent approximately 52,000 ft., with a cost to

replace of approximately $18.3 million. As an element of the City’s Pipeline (Main) Replacement

Program, these City-identified pipelines are flagged with a higher risk of failure, and should

receive priority funding under the sewer main replacement program activity. Discussions with

City staff suggest these improvements could be phased in over the next 12 years. It is

recommended that as part of the City’s CIP, candidate projects be selected from this list based

on other water main replacements/street paving projects to help the City align their

replacement program with other Departments.

Table 4 summarizes the recommended costs for the annual CIP recommendations over the next

5 years to meet the needs in the improvement categories. Of note, the 5-year CIP shown herein

is designed to combine the various improvements under the currently budget $3 Million per year

Main Replacement Program. With no additional funding required, this improvement program

could be seamlessly integrated in the City’s available CIP resources.

Table 4. 4-Year CIP Summary Description Year 1 Year 2 Year 3 Year 4 Year5

Capacity Improvements $2,000,000 $1,200,000 $1,600,000

$2,000,000

Field Review Services $100,000

$80,000

Pipeline Replacements $900,000 $1,800,000 $1,400,000 $2,920,000 $1,000,000

TOTAL ANNUAL CIP $3,000,000 $3,000,000 $3,000,000 $3,000,000 $3,000,000