December 2, 2005 Mr. Jeffrey Boring Big Thompson Watershed Forum 800 South Taft Avenue Loveland, CO 80537 Dear Jeffrey: We are pleased to submit the deliverables for Task 1 of the Mariano Exchange Ditch System Assessment Project. The deliverables are organized according to subtask, as described in the Statement of Work. Photographs taken during the site visits are also provided separately in four .zip files. We look forward to meeting with you and the planning committee on December 15 th or 16 th where we plan on discussing our findings and making recommendations. Please let me know if you have any questions or concerns that you would like to discuss prior to the meeting. I will send out an agenda after we settle on a final date and time. Sincerely, Hydrosphere Resource Consultants, Inc. by: Jean Marie Boyer, Ph.D., P.E.
Transcript
December 2, 2005
Mr. Jeffrey Boring Big Thompson Watershed Forum 800 South Taft Avenue Loveland, CO 80537
Dear Jeffrey:
We are pleased to submit the deliverables for Task 1 of the Mariano Exchange Ditch System Assessment Project. The deliverables are organized according to subtask, as described in the Statement of Work. Photographs taken during the site visits are also provided separately in four .zip files.
We look forward to meeting with you and the planning committee on December 15th or 16th where we plan on discussing our findings and making recommendations. Please let me know if you have any questions or concerns that you would like to discuss prior to the meeting. I will send out an agenda after we settle on a final date and time.
Sincerely, Hydrosphere Resource Consultants, Inc.
by: Jean Marie Boyer, Ph.D., P.E.
EXHIBIT A
Mariano Exchange Ditch System Assessment Project Scope of Work
Hydrosphere Resource Consultants September 7, 2005
PROJECT OBJECTIVES
The objective of this project is to:
1. Conduct an assessment of the Mariano Exchange Ditch System (MEDS) resulting in a preliminary description of water quality impacts from the MEDS to the Big Thompson River and the source(s) of these impacts.
Task 1 - Establish Existing Conditions
The purpose of this task is to identify, from existing information, site visits and initial sampling, 1) water quality impacts, 2) sources of water quality impacts, and 3) relative contribution of each source to the Big Thompson River. The operational schedule and current water rights context of the MED will be provided through interviews.
During this task, Hydrosphere will:
1.1 Collect and analyze grab water-quality samples at five sites. Data will be collected the week of September 12, 2005. The five sites include: 1) immediately below the reservoir outlet, 2) upstream of the most incised section of the MED, approximately 2000 feet below the reservoir outlet, 3) directly below the most incised section of the MED, 4) above the Wilson Avenue bridge (near SW 9 th Place), and, 5) in the MED at the confluence with the Big Thompson River. GPS readings of these sites will be documented. Water samples will be analyzed for non-volatile suspended solids, total suspended solids, turbidity, temperature, tota l phosphorus and total nitrogen. Discharge will be calculated based on readings at the gaging station located on the MED. These flows will be used to calculate total suspended solids, total phosphorus and total nitrogen loads at the time of sample collection. BTWF will provide 2005 MED flow data, if available. Hydrosphere will use these data to estimate total suspended solids, total phosphorus and total nitrogen loads for the 2005 flow season;
1.2 Gather background data including water quality data provided by the BTWF and the following reports/items from the City of Loveland: 1) Loveland stormwater map identifying each stormwater discharge into the MED, 2) as-built construction drawings for all capital improvement projects affecting the MED, 3) system drainage map including subbasin drainage
areas, and 4) MS4 information including the stormwater system map and attribute tables and Illicit Discharge Detection and Elimination Plan (in progress);
1.3 Conduct a water rights review to ascertain the current operational and water rights context of the MEDS. This review will be based on documents publicly available online from the State Engineer’s Office web site and interviews with the water commissioner for District 4, staff from the Consolidated Home Supply Ditch Company & Reservoir Company (Company) , and staff from the City of Loveland.
Based on information from the State’s water rights online database, Hydrosphere will identify the water rights associated with the Geroge Rist Ditch and Mariano (Boedecker) Reservoir and the Mariano Exchange Ditch, including each right’s appropriation date, adjudication date, instantaneous rate and volumetric limits. Hydrosphere will also tabulate the historical diversions by the George Rist Ditch, the Mariano Reservoir diversion, and the exchanges made from the outfall of Mariano Exchange Ditch to the George Rist headgate from records available electronically.
In the interview of the water commissioner, Hydrosphere will discuss the current operation of the MEDS, and any concerns or problems with the exchange that the commissioner may be aware of. To the extent allowed by electronically available water use records, Hydrosphere will identify which downstream water users are potentially affected by the operation of the exchange, where they are located, and what their water right(s) priority date(s) are.
Based on information from the water commissioner, Hydrosphere will generate a schematic (line diagram) of the river from the headgate of the George Rist Ditch down to the outfall of the Mariano Exchange Ditch, including the intervening water rights that actively divert water from the river. In addition, Hydrosphere will identify the junior water user(s) who most commonly divert the water supplied to the river by the Mariano Exchange Ditch, and the ditches within District 4 that historically received water from the exchange ditch, based on priority date. Ditches receiving water from the exchange ditch downstream of Division 4 will not be individually identified.
1.4 Conduct site visits of the MEDS. Hydrosphere will inventory and locate potential non-point sources of pollution and to field verify point-source discharges identified in the reports/items provided by the City of Loveland. GPS coordinates will be provided for all point-sources and potential non-point sources of pollution identified and other relevant features of the MED. In addition, one site visit will occur during stormwater conditions (weather permitting) to conduct visual inspections of stormwater contributions from the ditch to the Big Thompson River;
1.5 Collect five samples of soil from the MEDS (two from the ditch side walls , two from the bed in the incised reach, and one from the reservoir). The most representative samples from each location (one side wall sample , one bed sample, and one reservoir sample) will be evaluated to determine the classification and settling characteristics of the suspended sediment. Gradation and hydrometer tests will be conducted for these two samples to identify the fine sand component and to distinguish between silt and clay material. Sample settling rates will be compared with theoretical information for the classified material to define settling rates needed for the evaluation stage of work. Soil types will be defined for all soils tested for analysis in accordance with the United Soil Classification System;
1.6 Conduct topographic surveying to supplement the information provided to Hydrosphere by the City of Loveland (described in Task 1.2). The surveying information required for this sub-task includes 1) field surveying for up to four representative cross-sections at representative locations (sites to be determined by Hydrosphere based on site inspections) and 2) longitudinal profiles approximately 200 feet upstream and 200 feet downstream of the cross-section locations ;
1.7 Analyze and document the above information. The BTWF will be provided with a document that will include the raw data collected, calculations made, methodologies, and a text description of the water rights review. This document will be provided to the BTWF Project Manager electronically in Microsoft Word by 5 PM on December 2, 2005; and
1.8 Hold a meeting at the completion of this task to discuss the study results, additional sampling recommendations for the 2006 exchange water delivery season, and recommendations for subsequent tasks. The meeting will involve the BTWF Planning Committee and Hydrosphere. Hydrosphere will develop an agenda and presentation for this meeting that will be held in Hydrosphere’s Boulder office. The BTWF Project Manager will take minutes and distribute to the MEDS Planning Committee as requested.
BUDGET
The budget to conduct this work is $17,404. The breakdown by task is shown on the attached budget. Hydrosphere will not exceed this budgeted amount without written permission from BTWF. Hydrosphere will notify BTWF if work is requested outside this scope of work.
SCHEDULE
The project will be completed by January 31, 2006.
STAFFING AND SUPPORT
Hydrosphere commits the following staff to this project: Jean Marie Boyer, Doug Laiho, John Winchester, Laura Belanger and / or Kevin Wheeler and miscellaneous AutoCAD, GIS and administrative staff. All water quality samples will be analyzed at University of Colorado Center for Limnology Lab. Soil analyses will be conducted by the laboratory at Terracon Consultants. Ayres & Associates will conduct the topographic surveying tasks, as required. No changes regarding staff, sub-consultants, labs and analysis measures will be made without prior written consent of the BTWF Project Manager, which consent shall not be unreasonably withheld.
PROJECT MANAGEMENT AND COMMUNICATION
For purposes of this project, Mr. Jeffrey Boring is the BTWF Project Manager. Dr. Jean Marie Boyer is the Project Manager for the Consultant Team. Any formal notice or communication between the Consultant Team and the BTWF will be between the two Project Managers.
Note that if any item in this scope of work is in conflict with the main contract, this scope of work takes precedence.
Task 1.1: September Sampling
Mariano Exchange Ditch (MED) System Assessment Project Task 1.1 - Collect and Analyze Grab Water-Quality Samples at Five Sites September 12, 2005 Field Visit The purpose of this field visit was to quantify sediment loading by collecting water quality and field data at five sampling sites as described in the Scope of Work. The following were collected at each site: surface water samples; turbidimeter readings; air and water temperatures; GPS coordinates; photographs; and visual observations. In addition, a staff gage reading was made at the flume on the MED located just north of West 1st Street. Surface water samples were analyzed for total suspended solids, non-volatile suspended solids, total nitrogen, and total phosphorus. The water in the MED was cloudy at all sampling locations and the sampler (Laura Belanger) was unable to discern a visible difference in turbidity between sites. Water in Boedecker Reservoir at the outfall to the MED was sediment- laden and at the downstream end of the ditch a visible plume of sediment- laden water was apparent in the Big Thompson River originating at the MED. Pictures from this field visit can be found in the attached file: MEDPhotos - Site Visit 091205.zip
Mariano Exchange Ditch (MED) Site VisitSeptember 12, 2005
Laura Belanger
Field measurements are followed by Site Descriptions
Flow in the Big Thompson River just above the MED inflow per Fred Ritter at Loveland (estimation based on upstream gaged data and ditch/diversion data)
SiteTurbidity Readings
Site Descriptions
Staff Gage
Site 1
Site 2
Site 3
Site 4
Site 5
MED approximately 1/5 mile west (upstream) of Wilson Avenue bridge. Just at a bend below area with trees. Slightly less eroded as upstream area, banks are not as steep. Across for Ivy (St. or Ave) cul de sac. Location chosen to represent area just below most impacted (eroded) section of ditch. water is cloudy, grassy banks, visible erosion in places.
MED approximately 1/5 mile east (downstream) of Boedecker Reservoir. Banks are ~10 feet high. Site is located where MED starts to really become impacted (eroded). Was chosen to represent ares just above most impacted section of ditch. Grassy banks and along waters edge. Water is cloudy. Salt (?) line along northern bank. Marshy, muddy bottom.
MED at upstream end near Boedecker Reservoir outfall. Site located at downstream end (east) of culvert (~4 ft in diameter) under Crestone Drive. Large riprap covering banks and ditch bottom extending approximately 50 feet downstream. Water is cloudy.
Located at flume (a 10 foot Parshall flume according to Delbert) just to north (downstream) of 1st Avenue. Gage is between Sites 1 and 2.
MED approximately 50 feet upstream of confluence with the Big Thompson River (BT) Ditch is shaded and narrow then opens up for about 50 ft before entering the BT. The stream was cloudy and there was a very obvious plume entering the BT. The ditch bottom became very muddy as it narrowed. Sampled at spot where ditch just started to get wider. Ditch bank was well vegetated w/tall grasses, There was a red stringy algae (?) occupying the last foot of bank above the water line.
MED approximately 200 feet west (upstream) of the Wilson Avenue bridge. Bordered on south by open meadows and on north by older development. New development going on to NW of site. Some cattails and grasses, minimal riprap, some exposed soil. Stream was cloudy. Water from one of the Cattails reservoir (clear) enters the MED between Sites 2 and 3.
DON'T USE THE 1.40 cfs value (see note below)From "Isco Open Channel Flow Measurement Handbook" 3rd edition by Douglas M. Grant 10 ft Parshall FlumeCFS = 39.38H1.6
11/17/2005Laura spoke to Fred Ritter at Jeffrey Boring's suggestions. He said it's hard to read that outside staff gage at the flume and that there's a stilling point inside the gage house at the point. Using that reading he said the flow was 17 cfs (which better matches Delbert's 18 cfs).To confirm, the water was moving up and down at the gage on when the reading was taken so it was difficult to get a value.
Flow at flume on 9/12/2005 per Fred Ritter = 17 cfsFlow just above the MED on 9/12/2004 in the Big Thompson per Fred Ritter is estimated to be approximately = 42 cfs
Hydrosphere summary12-Sep-05
SITE TIME TDP, ppb TPP, ppb TP, ppb Total N, ppbDry mass
(TSS), mg/LAsh mass
(NVSS), mg/L AFDM, mg/L
#1 9:47 10.84 18.60 29.45 337 92.7 84.5 8.2
#2 10:35 10.84 18.34 29.18 384 46.9 40.7 6.2
#3 11:25 10.19 16.96 27.15 297 43.6 38.3 5.4
#4 12:20 10.19 17.27 27.46 313 47.9 42.0 5.9
#5 12:50 9.53 26.64 36.17 361 53.2 46.6 6.6
23 November 2005
Dr. Jean Marie BoyerHydrosphere Resource Consultants1002 Walnut, Suite 200Boulder, CO 80302
Dear Jean Marie:
Information on the following pages describes the analytical methods used in our laboratory and outlines QA/QC procedures associated with these analyses. Also, I am including information on the analytical performance (duplication) associated with selected tests. Performance data are included for samples analyzed for Hydrosphere and also for additional samples that were analyzed recently in our laboratory.
Sincerely,
James H. McCutchan, Jr.Associate DirectorCenter for Limnology
University of Colorado at Boulder
Cooperative Institute for Research in Environmental SciencesCenter for Limnology216 UCB
Boulder, Colorado 80309-0216
303-492-5191
Fax: 303-492-0928
Quality Assurance and Quality Control Procedures
Analytical methods used by the Center for Limnology are listed below (Table 1); original references describing the methods are given, along with reporting limits. Specific information on quality-assurance and quality-control procedures associated with the analyses are described below.
Sample handlingHandling of samples follows a standardized protocol. For samples collected by the Center
for Limnology, a record of sample collection is maintained in a field notebook. Samples for nutri-ent analyses are kept in a dark cooler until they reach the laboratory, where they are stored under refrigeration for 2 hours or less, at which time they are filtered (Whatman GF/C glass-fiber filters). Prior to use, all laboratory glassware and sample containers provided by the Center for Limnology are washed 5x with tap water and 5x with deionized water. Dedicated glassware is maintained for individual analytical tests (e.g., SRP, TDP, TPP, ammonia-N) and for individual standards.
For phosphorus analyses, the particulate component iss stored under desiccation pending digestion and analysis. A portion of the filtrate is analyzed immediately for SRP and TDP. The remaining filtrate is frozen at –20°C for subsequent batch analysis of ammonia, nitrate, and TDN. Samples for TN analysis are frozen separately at –20°C.
PhosphorusFor phosphorus analyses (SRP, TDP, and TPP), randomly selected samples (10%) are run in
duplicate. Also, randomly selected samples (10%) are run with a spike of known quantity. If the variation between duplicates exceeds 10% or if spike recovery is less than 90% (or greater than 110%), the samples are re-analyzed. Three-halves blanks are run with ordinary blanks to correct for reagent effects. Spikes and standards for phosphorus analyses are as follows: 19.5 µg/L for SRP, 22.2 µg/L (inorganic and organic) for TDP, and 20 µg/L for TPP. Any sample with an absor-bance > 0.8 is diluted and re-analyzed.
AmmoniaFor ammonia analyses, samples are run in triplicate. If absorbance values for a sample differ
from one another by more than 10%, the sample is reanalyzed. Randomly selected samples (10%) are analyzed in duplicate; 10% of samples also are analyzed with a spike of known quantity. If the variation between duplicates exceeds 10%, the samples are re-analyzed. If spike recovery is less than 90% or greater than 110%, the samples are re-analyzed. Standards for ammonia analyses are as follows: 20, 50, and 100 µg/L. Spikes are 50 µg/L. Any sample with an absorbance > 0.8 is diluted and re-analyzed.
Ion Chromatography (nitrate, total dissolved nitrogen, total nitrogen)Randomly selected samples (10%) are analyzed in duplicate; 10% of samples also are
analyzed with a spike of known quantity. If the variation between duplicates exceeds 10%, the samples are re-analyzed. If spike recovery is less than 90% or greater than 110%, the samples are re-analyzed. Nitrate standards for all analyses are as follows: 10, 25, 50, 100, 200, 500, 1000, and 2000 µg/L. For TDN and TN analyses, additional organic standards are as follows: 187 and 374 µg/L. Spikes for nitrate analyses are 200 µg/L and spikes for TDN and TN analyses are 187 µg/L. Any sample with a concentration > 2000 µg/L is diluted and reanalyzed.
ChlorophyllRandomly selected samples (10%) are analyzed in duplicate. If the variation between dupli-
cates exceeds 10%, the samples are re-analyzed. Any sample with an absorbance > 0.8 is diluted and re-analyzed.
Test Method References Reporting limitNutrient analyses
Nitrogen seriesAmmonia-N Modified Solarzano method Grashoff 1976 0.1 µg/LNitrate-N, Nitrite-N Ion chromatography 0.3 µg/LTotal dissolved N or total N
Oxidation with potassium persulfate followed by IC
Valderrama 1981; Davi et al. 1993
0.3 µg/L
Phosphorus seriesSoluble reactive P Ascorbic acid-molybdate
methodMurphey and Riley 1962
0.3 µg/L
Total dissolved P, Total particulate P
Oxidation followed by ascorbic acid-molybdate
Lagler and Hendrix 1982; Valderrama 1981; Murphey and Riley 1962
0.3 µg/L
Total P Sum of TDP and TPP 0.6 µg/L
Other analysesChlorophyll-a Hot ethanol extraction fol-
lowed by spectrophotom-etry
Marker et al. 1980; Nusch 1980
0.3 µg/L
Total suspended solids, AFDM, NVSS
Filtration (Whatman GF/C), gravimetric analysis
0.01 mg/L
Table 1. Summary of analytical methods. References are given below.
References
Davi, M.L., S. Bignami, C. Milan, M. Liboni, and M.G. Malfatto. 1993. Determination of nitrate in surface waters by ion-exchange chromatography after oxidation of total organic nitrogen to nitrate. Journal of Chromatography 644: 345-348.
Grashoff K. 1976. Methods of seawater analysis. Verlag Chmimie, Weinheim, pp 126-137
Lagler, C.L., and P.F. Hendrix. 1982. Evaluation of persulfate digestion method for particulate nitrogen and phosphorus. Water Research 16: 1451-1454.
Marker, A.F.H., E. A. Nusch, H. Rai, and B. Riemann, 1980. The measurement of photosynthetic pigments in freshwaters and standardization of methods: conclusions and recommendations. Archiv. fur Hydrobi-ologie, Beihefte, Ergebnisse der Limnologie 14: 91-106
Murphy, J., and J.P. Riley. 1962. A modified single solution method for the determination of phosphate in
natural waters. Anal. Chim. Acta 27: 31-36
Nusch, E. A. 1980. Comparison of different methods for chlorophyll and phaeopigment determination. Ar-chiv. fur Hydrobiologie, Beihefte, Ergebnisse der Limnologie 14: 14-36.
Valderrama, J. C. 1981. The simultaneous analysis of total nitrogen and phosphorus in natural waters. Ma-rine Chem. 10: 109-122.
Performance data
Performance data (duplication) for nitrogen and phosphorus analyses are given below (Figures 1 and 2). Data included in these figures are for samples analyzed for Hydrosphere and for additional samples that were analyzed recently in our laboratory.
1
0.5
10
5
3
2
20
30
Sol
uble
rea
ctiv
e P
(du
plic
ate)
, ug/
L
1 0.5 10 5 4 3 2 20 30
Soluble reactive P, ug/L
Log10
(Dup) = 0.0932 + 0.895 Log10
(Conc)r2 = 0.978, p < 0.0001
1
10
5
4
3
2
20
Tot
al d
isso
lved
P (
dupl
icat
e), u
g/L
1 10 5 4 3 2 20
Total dissolved P, ug/L
Log10
(Dup) = 0.00442 + 0.995 Log10
(Conc)r2 = 0.977, p <0.0001
Figure 1. Duplication for soluble reactive P (SRP) and total dissolved P (TDP).
Total N, ug/L
Log10
(Dup) = -0.0253 + 1.007 Log10
(Conc)r2= 0.999, p < 0.0001
1
104
10040
1000400
100004000
10000040000
Nitr
ate-
N (
dupl
icat
e), u
g/L
1 10 5 2 100 40 1000 10000
Nitrate-N, ug/L
100000
Log10
(Dup) = -0.0183 +1.00 Log10
(Conc)r2 = 0.999, p < 0.0001
Tota
l N (
dupl
icat
e), u
g/L
100
1000
500
300
200
10000
5000
3000
2000
Tota
l dis
solv
ed N
(du
plic
ate)
, ug/
L
100 1000 500 300 10000 4000 2000
Total dissolved N, ug/L
Log10
(Dup) = -0.0171 + 0.999 Log10
(Conc)r2= 0.970, p < 0.0001
100
1000
500
300200
10000
5000
30002000
100000
50000
3000020000
100 1000 400 200 10000 4000 100000
Figure 2. Performance data (duplication) for nitrogen analyses
Mariano Exchange Ditch Monitoring -- September 12, 2005Summary of Results
Date of Sampling: 9/12/2005Ditch Flow: 17 cfsBT Flow: 42 cfsSampler: Laura Belanger, HydrosphereLaboratory: Center for Limnology, University of ColoradoField Parameters: Water Temperature, Turbidity, Air TemperatureLab Parameters: TDP, TPP, TN, TSS, VSSSee Field Data Description for more details
* Assume TSS, TN, and TP concentrations measured on 9/12/05 apply for the 2005 flow season
(This assumption may not apply because the concentration may vary with flow and operations.
Additional data collection is needed to better estimate concentrations over the flow season.)
** Average daily flow for 2005 (per Fred Renner spreadsheet)
*** Ditch ran 63 days in 2005 (per Fred Renner spreadsheet)
Task 1.2: Gather Background Data
Data Collected
Mariano Exchange Ditch (MED) System Assessment Project Task 1.2 - Gather Background Data to Establish Existing Conditions
Data in Scope of WorkItem Received? Description Source1 Comment
1) Stormwater map YesStormwater map identifying each stormwater discharge into the MED 1
Aerial photo with known stormwater system structures identified.
2) As-built construction drawings NoAs build construction drawings for all capital improvement projects affecting the MED 1
Per Joe Chaplin (City of Loveland), without a specific request, it would be difficult to gather this information. No drawing were requested, though some may be at later date.
3) System drainage map PartialSystem drainage map including subbasin drainage areas 1, 2
A map covering the MED from Boedecker Reservoir to Wilson Avenue was provided in the Ayres Report. Per Joe Chaplin, drainage area information on the rest of the ditch was unavailable.
4) MS4 information No
MS4 information including the stormwater system map and attribute tables and Illicit Discharge and Elimination Plan 1
Per Joe Chaplin, these documents are still being written/revised so are currently unavailable.
1 See attached Source key
Additional Data CollectedItem Received? Description Source1
MED HEC-RAS Model YesHEC-RAS surface water model of Mariano Exchange Ditch 1
Wind and precipitation data YesDaily (Olde Golf Course) and 10 minute interval (1st and Taft) weather data 3, 4
Wilson Avenue Mariano Exchange Ditch Culvert Replacement Design Report Yes
Report on 2004 Wilson Avenue culvert replacement, includes detailed MED data 2
Mariano Reservoir Dam Rehabilitation Report and photographs Yes
Report on Boedecker Reservoir dam work completed in 2003 and related photographs 5
Larimer County soils report Yes 1980 soils survey report of Larimer County 6MED area soils map Yes MED area soils map 7Boedecker Reservoir observation forms Pending
Site observations of the reservoir being made by Delbert Helzer 8
MED related water quality data YesWater quality data for the MED and Big Thompson River in the vicinity of the MED 9
General background information Yes
General background data regarding Boedecker reservoir and the MED gathered during multiple conversations with Delbert Helzer 10
USGS topographical maps Yes Topographical maps of the Loveland area 11
Aerial photo of Boedecker Reservoir YesAerial photo of Boedecker Reservoir during draw down for dam work 12
2000 - 2005 Daily MED flows YesAverage daily flows for water years 2000 through 2005 for the MED at the 1st Street flume 13
1 See attached Source key
Task 1.3: Water Rights Review
Hydrosphere Resource Consultants, Inc.
Boulder CO – Socorro, NM 303-443-7839 505-835-2569
A Water Rights and Operations Review of Mariano Reservoir and Exchange Ditch
1.0 Background The Home Supply Ditch diverts water from the Big Thompson River at the mouth of the Big Thompson Canyon, near Loveland, Colorado, and supplies water to agricultural users. To increase the reliability of the ditch’s water supply, the ditch can store water in three reservoirs, Lon Hagler Reservoir, Lonetree Reservoir, and Mariano Reservoir. All three reservoirs store water during the snowmelt runoff season. Unlike the Lonetree Reservoir, Mariano and Lon Hagler reservoirs do not deliver water directly to the irrigated lands, but release water to the Big Thompson River. As water is released to the river, a like amount is diverted at the Home Supply Ditch via a rive r exchange, which is operated so as not to injure senior water rights holders. Lon Hagler Reservoir delivers water to Mariano Reservoir via pipeline, which in turn releases the water to the river. The exchange of water between the Mariano Exchange Ditch and the Home Supply headgate is decreed in water court, and administered in priority with the other water rights on the Big Thompson River.1 When releases are made from Mariano Reservoir to the Big Thompson, the water coming from the Mariano Exchange Ditch is typically cloudy with fine silt. Where the exchange ditch meets the Big Thompson River, the difference in water quality commonly pronounced. This document provides a review of the water rights associated with the Home Supply Ditch, Mariano Reservoir and the other water rights on the Big Thompson, to determine if opportunities exist whereby operation of the Mariano exchange could be modified to improve water quality, without injuring senior water rights. This effort involved the development of a straight line diagram which includes water transfers (HRC Straight Line Diagram.ppt). The State’s Division 1, District 4 straight line diagram, which describes original water rights and was needed to develop the straight line diagram including water transfers, is also provided (District4_StraightLine_20050719.pdf).
2.0 Area Water Rights Water rights in Colorado are administered under the prior appropriation system, which gives “the party who first puts water to a beneficial use the right to use the water to the exclusion of others.”2
1 Telephone conversation with Delbert Helzer, general manager of the Home Supply Ditch, on Oct 24, 2005. 2 Sandra H. Johnson ET AL., Property Law: Cases, Materials and Problems 28-29 (2nd ed. 1998).
Mariano Exchange Ditch Water Operations and Water Rights Page 2 of 9 October 25 2005
Hydrosphere Resource Consultants, Inc.
Boulder CO – Socorro, NM 303-443-7839 505-835-2569
In order to acquire a water right with a legally enforceable priority under Colorado law, a water user must put the water to a beneficial use and have that appropriation adjudicated in water court. The court issues a decree for the water right that states the priority for right, the specific uses the right may be used for, and the amount of water that may be used. The priority date is based on a combination of the adjudication and appropriation dates.3
Home Supply Ditch The Home Supply Ditch has nine direct flow water rights, plus is listed as the terminus for fifteen alternate points of diversion. The ditches direct flow rights have a cumulative capacity of 903.96 cfs, with adjudication dates between 1883 and 1987, and appropriation dates between 1861 and 1907. Including the alternate points of diversion, the ditch has a total decreed capacity of 1570.71 cfs. The ditch has an estimated capacity of 325 cfs.4
Mariano Reservoir In addition to the rights decreed for the Home Supply Ditch, the ditch also carries water to Mariano Reservoir. The reservoir has two decrees, the more senior for 11,141.4 acre-feet with an adjudication date of 1883 and the junior for 5,507.7 acre-feet with an adjudication date of 1939.
Lon Hagler Reservoir The Home Supply Ditch also carries water to Lon Hagler Reservoir, which releases exchange water via Mariano Reservoir. Lon Hagler is a comparatively junior right, with two rights, an absolute right for 5,307 acre-feet with an adjudication date of 1970, and a conditional right for 3,529 acre-feet with an adjudication right of 1980.
Mariano Exchange Ditch The Home Supply Ditch Company holds a decree for exchanging water from the outfall of the Mariano Exchange Ditch to the headgate of the Home Supply Ditch. The adjudication and appropriation dates for the exchange decree were not available on- line. Three other ditches on this reach of the Big Thompson exchange water from reservoirs to headgates, the most frequent being from the outlet of Ryan Gulch Lake to the headgate of the South Side Ditch. 5
3 Lawrence J. MacDonnell, Five Principals that Define Colorado Water Law, 26 Colo. Law. 165, 165-167 (1997). 4 Hydrobase, database for the Colorado Decision Support Systems. http://cdss.state.co.us/DNN/WaterRights/tabid/76/Default.aspx 5 Telephone conversation with Les Dalby, Colorado State Engineer’s Office, Division 2, Greeley Colorado, on Oct 25, 2005.
Mariano Exchange Ditch Water Operations and Water Rights Page 3 of 9 October 25 2005
Hydrosphere Resource Consultants, Inc.
Boulder CO – Socorro, NM 303-443-7839 505-835-2569
3.0 Typical Operations The Home Supply Ditch is used to convey water to irrigated agricultural lands. The ditch diverts water year-round, delivering water to the fields during the growing season, and to the reservoirs during the non- irrigation season.
Home Supply Ditch The Home Supply Ditch physically diverts water from the Big Thompson year-round. As shown in Table 1, prior to 1971 the ditch diverted direct flow rights for use during the irrigation season. For the past 35 years, the ditch has diverted water throughout the year, for direct use during the summer and reservoir storage during the winter. The values in Table 1 include diversions under the ditch’s water rights, diversions of exchanged water, and diversions of water leased from other entities, such as the Colorado Big-Thompson Project.
Mariano Exchange Ditch Water Operations and Water Rights Page 4 of 9 October 25 2005
Hydrosphere Resource Consultants, Inc.
Boulder CO – Socorro, NM 303-443-7839 505-835-2569
Table 1. Home Supply Ditch Historical Diversions6
6 Hydrobase, database for the Colorado Decision Support Systems. http://cdss.state.co.us/DNN/Structures/tabid/75/Default.aspx
Mariano Exchange Ditch Water Operations and Water Rights Page 5 of 9 October 25 2005
Hydrosphere Resource Consultants, Inc.
Boulder CO – Socorro, NM 303-443-7839 505-835-2569
Mariano Reservoir Because water from Lon Hagler Reservoir can only be released to Mariano Reservoir and exchanged back to the Home Supply headgate, Mariano and Lon Hagler reservoirs operationally act as one reservoir. The reservoirs are filled as early as possible during the fall and winter, and release water predominantly during July and Augus t. Table 2 and Table 3 show the diversions to storage in Mariano and Lon Hagler reservoirs, respectively, for the period of record publicly available on- line. Records of Mariano Reservoir and Lon Hagler Reservoir contents were not available on-line. Table 2. Mariano Reservoir Diversions (af/mo)
Table 3. Lon Hagler Reservoir Diversions (af/m0)
Mariano Exchange The Home Supply Ditch diverts part of its water from water rights that were transferred to the Home Supply from other ditches. One of the transfer decrees specifies that the Home Supply Ditch can only divert transferred water through July 14. Consequently, the Mariano Exchange typically begins in the middle of July and runs until the reservoir is drawn down, or until the demand for irrigation water ends.7 Table 4 shows the recorded exchanges by month for the last 55 years. The Mariano Exchange is typically begun at 50 cfs, and is occasionally run as high as 60 or 70 cfs. The exchange is estimated to be physically limited to 90 cfs, due to a restriction at the box culvert that carries the ditch under Wilson Avenue. The water released by the exchange physically satisfies the ditches just downstream of the exchange ditch, including the Loveland and Greeley Ditch, the Big Thompson Ditch Co., and the Farmers Irrigation Canal.8
7 Telephone conversation with Delbert Helzer, manager of the Home Supply Ditch, Oct 24, 2005. 8 Telephone conversation with Fred Renner, District 4 Water Commissioner, Oct 20, 2005.
Mariano Exchange Ditch Water Operations and Water Rights Page 6 of 9 October 25 2005
Hydrosphere Resource Consultants, Inc.
Boulder CO – Socorro, NM 303-443-7839 505-835-2569
Table 4. Mariano Reservoir Exchanges to Home Supply Headgate (af/mo)9
River Call The call record for the Big Thompson was obtained from the Colorado Department of Water Resources’ web site, which was available electronically for the period July 1997 through September 2005. Table 5 shows summarizes the most frequently calling structure by month and year.
9 Provided by Les Dalby, Colorado State Engineer’s Office, Division 2, Greeley, Colorado.
Mariano Exchange Ditch Water Operations and Water Rights Page 7 of 9 October 25 2005
Hydrosphere Resource Consultants, Inc.
Boulder CO – Socorro, NM 303-443-7839 505-835-2569
Table 5. ID of most Frequently Calling Ditch
The table shows that during July and August, the months the Mariano Exchange Ditch supplies replacement to the Big Thompson, the Loveland Greeley Canal is most frequently the calling right on the river. The Loveland Greeley is the second diversion downstream from the Mariano Exchange Ditch.
4.0 Potential Changes in Operations The purpose of this water rights and operations review is to determine what changes, if any, can be made in the operation of the Mariano Exchange to improve the water quality of water coming from the exchange ditch. The following sections examine three potential modifications to operations that could be employed to improve water quality.
Store and Release at Different Times There are ditch systems in Colorado that have modified their operations by changing which rights they diverted at particular times of the year, using junior rights during times of high flows to fill reservoirs, and then using their senior rights during periods of lower flows. These changes in accounting allowed the ditches to continue to divert year-round without having to augment their use. Mariano Reservoir and the Mariano Exchange were built and decreed to store water during one season for use in another. Because streamflows generally decline in July and August, rearranging the diversion pattern from the river is unlikely to be possible without injuring senior rights. Thoroughly researching the possibility of reoperating multiple ditches is beyond the resources available under this contract.
Store in Different Reservoir Storing water in a reservoir other than Mariano Reservoir would reduce or eliminate the releases made down the Exchange Ditch, which in turn would reduce the amount of cloudy water released to the Big Thompson River. Water could be stored in a reservoir under the Home Supply Ditch or under another ditch.
Mariano Exchange Ditch Water Operations and Water Rights Page 8 of 9 October 25 2005
Hydrosphere Resource Consultants, Inc.
Boulder CO – Socorro, NM 303-443-7839 505-835-2569
The Home Supply Ditch operates three reservoirs, Lon Hagler, Mariano and Lonetree. Because both Lon Hagler and Mariano reservoirs are used as exchange reservoirs, their combined space of 21,957 acre-feet would have to be replaced in Lonetree reservoir. Because the current size of Lonetree reservoir is 9,211 acre-feet, replacing the storage in Lon Hagler and Mariano would require a significant enlargement of Lonetree Reservoir or construction of a new reservoir, which may or may not be physically or economically feasible. Based on records from the State Engineer’s Office, only one reservoir between the mouth of the Big Thompson Canyon and the confluence with the South Platte River has a capacity of 22,000 acre-feet or more of water. Boyd Reservoir, an existing reservoir north of the river, has a capacity of 92,600 acre-feet. According to the Colorado Division of Water Resources ditch map for District 410, Boyd Lake can supply water to the Loveland Greeley Canal. Assuming there is space in Boyd Lake to store the water currently stored in Mariano Reservoir, and assuming the facilities to release the water from Boyd Lake to the Loveland Greeley Canal are in place, one alternative would be to store water from Mariano Reservoir in Boyd Lake, which would preclude the release of water down the Mariano Exchange Ditch. While it may be possible to assemble the required storage in multiple reservoirs, such an arrangement would be complicated by two factors: first, the accounting for the Home Supply Ditch water in other reservoirs would be directly proportional to the number of cooperating water users, and second, because of their senior water rights, the other reservoirs on the river usually fill under their own rights, and as such, don’t have empty space to allocate to Home Supply Ditch water. To determine if storing Home Supply water in Boyd Reservoir is feasible, a more detailed study of the operation of Boyd Reservoir is required.
Reservoir Pump-back An alternative that would maintain water storage in Mariano Reservoir while reducing or eliminating sediment load associated with exchange releases would be to install a reservoir pump-back system, where water would be pumped directly from Mariano and Lon Hagler reservoirs back into the Home Supply Canal. Assuming the intake at Mariano would be near the geographical center of the lake, the pump-back system would need to move water approximately 2/3 of a mile, with an elevation gain of approximately 120 feet. The gains in water quality from this alternative are heavily dependant on the source of the entrained sediment. If the sediment originates in the lake itself, then a pump-back would eliminate the sediment problem. If the sediment originates in the lower reaches of the ditch, then sediment would be reduced, but storm runoff from neighborhoods that drains to the ditch would still pick up some sediment.
Mariano Exchange Ditch Water Operations and Water Rights Page 9 of 9 October 25 2005
Hydrosphere Resource Consultants, Inc.
Boulder CO – Socorro, NM 303-443-7839 505-835-2569
There are several benefits of this alternative, including:
1. It keeps at least some of the sediment out of the Big Thompson River, and 2. The delivery of water from the outfall of the exchange ditch to the Home Supply
Ditch is not dependent on river flows. Disadvantages are:
1. There would be a capital investment required to install a pump and pipeline, and 2. There would be on-going costs to maintain and run the pump-back system.
5.0 Conclusion While there are not numerous alternatives to the Mariano exchange that has occurred historically, there are at least two which may be worth further consideration, the storage of water in Boyd Lake and pumping water from Mariano Reservoir back to the Home Supply Ditch. To determine if either of these alternatives is feasible, more detailed study should be made to determine the availability of storage space in Boyd Lake, and the probable cost of building and operating a pump-back system from Mariano Reservoir.
Big Thompson River
16.7
Hill & Brus
h Ditc
h
27.0
cfs– ap
p 06/3
0/186
6 //
21.9
Hillsboro Ditch
63.31 cfs – 11/10/1861 // adj 05/28/1883
8.25 cfs – 10/15/1874 // adj 05/28/1883
54.0 cfs – 04/15/1878 // adj 05/28/1883
45.69 cfs – 10/06/1881 // adj 05/28/1883
100.0 cfs – 10/20/1896 // adj 03/22/1890
13.0 cfs – 02/01/1926 // adj 12/31/1969
Farm
ers D
itch
4.0 c
fs- app
11/10
/1861
//
adj05/
28/188
3
1.78
cfs- app
04/01
/1863
//
adj05/
28/188
3
7.67
cfs- app
05/01
/1864
//
adj05/
28/188
3
3.44
cfs- app
03/01
/1867
//
adj05/
28/188
3
2.6 cf
s- app
06/01
/1868
//
adj05/
28/188
3
0.51
cfs- app
05/01
/1872
//
adj05/
28/188
3
54.08
cfs- a
pp 08/
01/187
8 //
adj05/
28/188
3
Love
land &
Gree
ley C
anal
05/28/
1883
29
7.44
cfs- app
04/01
/1881
//
adj05/
28/188
3
05/28/
1883
49
.28
cfs- app
05/01
/1890
//
adj11/
14/193
9
05/28/
1883
445.
97
cfs- app
04/28
/1902
//
adj06/
29/191
6
Big Thompson Ditch & Mfg
app 04/01/1863 // adj 05/28/1883
app 05/01/1864 // adj 05/28/1883
app 03/01/1867 // adj 05/28/1883
app 05/01/1872 // adj 05/28/1883
Rist & Goss Ditch
6.406 cfs - app 03/20/1866 // adj 05/28/1883
53.38 cfs - app 04/15/1875 // adj 05/28/1883
Gaging StationBig Thompson R at Loveland#06741510, avail 1979-2004
Mariano Exchange Ditch (MED) System Assessment Project Task 1.4 - Conduct Site Visits of the MEDS Site Visit Descriptions October 10, 2005 A site visit was made by Doug Laiho specifically to observe ditch physical and hydraulic conditions at the time of a significant rainfall. The MED was expected to be under conditions where irrigation flows were essentially absent, having been terminated three weeks earlier and essentially all flow could be attributed to rainfall runoff. The visit occurred under steady rain conditions from a general storm that had begun almost thirty hours earlier, with low intensity rain having fallen continuously during the period. This event was not a high intensity, short duration thunderstorm, which would be more typical of this time of the year, nor did it have a thunderstorm embedded within it. Such a thunderstorm event would be expected to have a more dramatic impact on the MED hydraulic capacity and physical conditions than a general storm. Rain was actively falling and water was actively running off the ground surface at the time of the visit. The notable observations which were made include:
• There was noticeable flow (considerably less than when irrigation water is being carried) in the MED with a staff gage reading of 0.22’ being made at 12:15 p.m.
• Pictures in file “MEDPhotos - Site Visit 101005 - Rainfall.zip” were taken during the visit.
• Flow from the MED at the confluence with the Big Thompson River had only slightly higher visual turbidity than water in the River; most people would probably consider both flows to be only slightly turbid or essentially clear
• By observation (versus measurement) approximately ¼ of the flow observed at the gage originated out of Boedecker Reservoir outlet structure and the remainder from the Cattail Dam #2 outfall. It is assumed that flow from the Reservoir was due to gate leakage as irrigation flows had been terminated for the season. Flow from Boedecker Reservoir was observed to be slightly turbid (green, milky, light brown in color) and flow from Cattail Dam #2 was essentially clear. There was no noticeable turbidity change along the length of the MED to the confluence that would indicate significant sediment was being picked up from the MED bottom or side slopes.
• A light wind occurring at the time of the visit (estimated at 20 km/hr) was producing small waves on the reservoir surface. The reservoir surface level was shallow, only just covering the outlet, but the waves were probably not large enough to be picking up sediment by bottom friction. The Reservoir water did not appear to be turbid at the outlet.
• Water was flowing into the Reservoir via its inlet channel at a rate estimated to be approximately 10 cfs. This water had a very obvious dark grey turbidity, typical of what one would observe as “first flush” runoff from urban streets after a long period without rainfall runoff. This observation was a surprise and the source of this colored water was not obvious or further investigated.
October 27, 2005 An opportunistic site visit was made by Doug Laiho when he was in the vicinity for a different primary purpose, to obtain improved site familiarity and to observe MED physical conditions approximately a month after the seasonal cessation of exchange water deliveries. This site visit was expected to be under conditions where the MED should be essentially dry. The notable observations which were made include:
• There was noticeable flow (less than the 10/10/05 visit and considerably less than when irrigation water is being carried) in the MED with a staff gage reading of 0.16’ being made ad 5:45 p.m.
• A large block or mass wasting type failure had occurred between structures H11 and H12 (see attached Revised Stormwater Structures Map) since the last site visit. While bare, erosion prone banks have been observed previously, this was the first opportunity to examine an incidence of bank erosion. This instance of bank erosion is probably typical of this area and similar areas dominated by a cohesive soil material (clay, in this case). This process has been observed on natural streams (such as Elkhead Creek in Colorado and Nemadji River in Wisconsin) and results in an essentially perpetually turbid water condition. A large block of soil had dropped from the right bank along a nearly vertical failure plane, falling to the channel bed at the toe of the slope. This classic “plane slip” type mass wasting was probably caused by a combination of hydraulic and geotechnical factors. It is likely that water flow in the ditch, including secondary currents, eroded bank edge material from the toe of the failure surface reducing support for the material above it. Upon cessation of irrigation flows for the season a portion of this undercut bank edge was left with high residual soil-water pressure, unsupported by water in the MED. With the underlying sub-soil clay reduced in volume and unable to drain quickly enough to relieve the pore pressure, the overburden soil wedge can no longer be supported by the soil below and fails vertically and slightly ditch-ward into the channel bottom. This can temporarily stabilize this slope, but deflects the ditch flow against the opposite bank and the process is repeated. This produces a readily available source of sediment in the channel bottom which will likely show up as turbidity when normal flow returns to the ditch.
• The stream bed upstream of Wilson Avenue has the appearance of a flat pool-riffle sequence with 5’ to 20’ long riffles dropping the bed an inch or two, separated approximately every fifty feet by a flatter gradient run or pool No
channel grade breaks or head-cuts of more than an inch or two were observed in the channel bottom. This resulting overall flat sloped channel bottom may be subject to small dynamic changes, but is not likely in a condition of continuing degradation. Upstream of Wilson Avenue, the channel bottom is bare, unarmored and the sidewalls are approximately 50% vegetated. Downstream of Wilson Avenue the channel bottom is bare, unarmored and the sidewalls are more completely vegetated. Occasional vertical side walls exist primarily on north facing exposures. The top eight feet of these side walls appears to be fine material dominated by clay and the lower four feet is primarily clay with some sand, transitioning to weathered siltstone/claystone. This lower level holds a one foot capillary fringe of water above the water level. Some stringy algae are present in the MED bed in the vicinity of First Street.
• What appears to be an almost free-standing grouted rock energy dissipater exists opposite an off-channel detention pond outlet at Hydrosphere's structure H12 (see Revised Stormwater Structures Map and descriptions provided with this deliverable). The dissipater has been completely eroded behind and on each end, but is partly supported at its base. This condition, while a severe example, is typical of structures at locations where off-site flows are discharged to the MED via structures along the unstable ditch walls.
• Pictures file “MEDPhotos - Site Visit 102705” were taken during the visit, including views of bullets one and three preceding.
November 1, 2005 The purpose of this site visit (by Laura Belanger) was to locate and verify stormwater structures draining to the MED as provided by the City of Loveland (Loveland) on a stormwater system map. Other possible point and non-point sources were also identified. Soil samples were collected at Boedecker Reservoir and from the MED bank and channel bottom in an eroded section of the ditch. The entire length of the ditch was walked, with the exception of the final northern extent of the ditch from the location where it emerges from below ground in the vicinity of the school bus parking lot and recycling center to where it enters the Big Thompson. This section was not examined due to failing daylight, its minimal extent, and no stormwater inflows being identified for it on Loveland's map. The lower 60 feet of this section of ditch was examined during the 9/12/2005 site vis it and no stormwater outfalls were identified at that time. Pictures from this field visit can be found in the file: MEDPhotos - Site Visit 110105.zip (Note that pictures referenced below are found in this file) The following is a summary of major findings during the November 2005 site visit.
• Undocumented Stormwater Inflows to MED: Numerous point source stormwater inflows were not identified on Loveland's map. It appears that the majoring of outfalls on the map were those drainage recent developments. There were numerous unidentified stormwater structures between Boedecker Reservoir and South Wilson Avenue, with only a few to the east of Wilson (pictures: 034, 035, 036, 037, 038, 040, 041, 042, 043, 047, 048, 049, 050, 051, 057, 058, 076, 077, 078, 109 and 110). Information on unidentified outfalls, along with GPS coordinates and descriptions, is provided in the attached Revised Stormwater Structures Map and the Stormwater Structure Descriptions document. Outfalls on the stormwater map were also found to be inconsistently represented (for example, some were identified as pipes and others as pipes followed by outfalls, though the structures were physically the same). Recommended edits are included in the Stormwater Structure Descriptions document.
• Block Failures: Large blocks of soil have fallen into the MED at points between
Boedecker Reservoir and South Wilson Avenue (pictures: 030, 053, 054, 055, 062 and 063). Stream banks in the steepest and most eroded sections of the ditch have visible fractures where it is assumed that additional blocks will eventually break free. In addition to serving as a source of sedimentation, this situation is extremely dangerous for anyone walking along these sections of the ditch.
• Possible Need for Additional Outfall(s): There is ongoing development occurring
along the northern side of the MED to the west of South Wilson Avenue. The existing but newer neighborhood located here has good drainage along its eastern and western ends (pictures: 058, 060, 070, 071 and 072). However, the middle section is not properly drained which has led to the development of natural drainages eroding the northern bank (pictures: 061, 073 and 074).
• MED Erosion to East of South Wilson Avenue : Erosion is occurring at points
along the entire MED. To the east of Wilson Avenue, the greatest erosion appears to be occurring in the vicinity of the Walt Clark Middle School grounds, where ditch banks are steep (pictures: 083, 084, 085 and 086). Erosion and undercutting occurs at various points along the entire eastern section of the MED (pictures: 089, 090 and 091). There is also some degradation of the stream channel in two sections (pictures: 088, 092, 093, 094, 113 and 114).
• Erosion Due to Older Stormwater Outfalls: Numerous older stormwater outfall
pipes located between Boedecker Reservoir and Wilson Avenue emerge high on the ditch wall with no grading or other mechanism in place to dissipate energy from stormwater flows. The most severe erosion has occurred around a pipe draining an established farm property to the north of the MED along the westernmost section of ditch (pictures: 034, 035, 036, and 037). It appears that breaks in this pipe may be causing erosion to occur from within the ditch bank.
In addition, soil has eroded around an older outfall located at the Walt Clark Middle School (Structure M4 on the Revised Stormwater Structures Map).
Stormwater Structure DescriptionsStormwater Structures Draining to the Mariano Exchange Ditch (MED)
Task 1.4 - Conduct Site Visits of the MEDS
Lat (°N) Long (°W)ResOut 40.38474 -105.13049 NA No Location of outfall structure to the MED at Boedecker Reservoir.
H1 40.38472 -105.13042 RipRap/Wetland NA No
May not wish to identify as stormwater structure on map. Constructed wetland draining from Buckingham Ditch (and road?) into MED in riprapped area between Boedecker outfall and culvert below S. Crestone Drive.
H4 40.38453 -105.12827 PVC Pipe 4 NoDrains property to north of ditch. There is a lot of erosion occurring underneath this pipe.
H5 40.38444 -105.12801 PVC Pipe 8 No Drains open lands to south of ditchH7 40.38499 -105.12678 Metal 2 No Drains property to north of ditch.
H11 40.38409 -105.12331 Overflow Structure? 4 No
Cement structure located on south side of ditch. Houses metal pipe workings with a 4" opening. Small cover reads "Water 125". Is a blowoff valve for potable water system?
H12 40.38352 -105.12137 Corrugated Plastic 18 No Drains new development on north side of ditch.
M1 P7810 40.38214 -105.11753 Corrugated Metal (2) 15 Yes
There are two 15" pipes side by side at this location. Both drain the reservoir to their south. Should be "Outfalls" to be consistent with other labeled structures.
It was a little difficult to measure the diameter of outfall as ends in a rubber backflow preventer. Need to switch the order of P6816 and OF1023. Pipe comes first then outfall is adjacent to the Mariano Exchange Ditch.
M3Wilson I4084 40.38244 -105.11561 NA Yes Culvert routing MED under Wilson.
H14 40.38296 -105.11439 Corrugated Metal 15 NoDrains a few houses, parking lot, maybe part of school grounds on south side of ditch.
M4 OF1022 40.38325 -105.11431 Corrugated Metal 18 YesErosion has left much of pipe exposed, may have leak causing soil around it to erode.
Intake 40.38752 -105.11295 Black Plastic Pipe 1.5 No
May not want this on stormwater map. It appears that water from this intake pipe is used to water the school grounds/fields (sign at school says untreated water is being applied).
M5 OF1003 40.38844 -105.11021 Corrugated Plastic 18 Yes Drains newer development on north side of ditch.
H15 40.38837 -105.10741 Corrugated Metal (3) 16 NoThere are three 16" metal pipes, side by side, draining older neighborhood to south of ditch. Discharge onto riprap approximately 10 feet from the ditch.
M6 OF1006 40.38851 -105.10797 Corrugated Plastic 18 Yes Drains newer development on north side of ditch.
M7 P3580 40.39018 -105.10845 Corrugated Plastic 18 YesShould be an "Outfall" (not "Pipe") to be consistent with other labeled structures. Drains newer development on west side of ditch.
M8 P3581 40.39080 -105.10902 Corrugated Plastic 18 YesShould be an "Outfall" (not "Pipe") to be consistent with other labeled structures. Drains newer development on west side of ditch.
M9 OF1388 40.39156 -105.10997 Corrugated Plastic 18 Yes Drains newer development on west side of ditch.M10 OF1387 40.39226 -105.11037 Corrugated Plastic 18 Yes Drains newer development on west side of ditch.
BusParking 40.39433 -105.11060 NA NoLocation where the MED goes underground to the north of W 1st Street and the gaging station (just south of lot where school buses are parked).
Natural Runoff Area of Potential Concern
H13 40.38273 -105.11970 Natural drainage NoNatural drainage which has formed along new development to north of MED. May need additional stormwater structure here.
2 In a 11/17/2005 phone conversation with Hydrosphere (Laura Belanger), Shannon Smith (Loveland's GIS staff person) said her understanding was that any structure discharging to the MED, regardless of material, should be considered an "Outfall". If this is the case, then all structures above, with the exception of "ResOut", "H1", "M3Wilson" and "BusParking" should be given "Outfall" IDs.
Identified on original
stormwater map received from
Loveland? Comments2
1 Stormwater structures, other structures, and sampling locations were first plotted on the Revised Stormwater Structure Map (provided by Hydrosphere) using GPS coordinates obtained during site visits. The placement of sites on the map was then manually adjusted to corrected for any error in GPS coordinates.
GPS Coordinates1
Hydrosphere Site Visit ID
Loveland Stormwater Structure ID Material
Diameter (inches)
Task 1.5: Soil Evaluation
Mariano Exchange Ditch (MED) System Assessment Project
Task 1.5 - Evaluate MED Soils
The evaluation of soils along the MED involved three components; review of the Larimer County Soil Survey (USDA 1980), review of information in the Ayres (2004) hydraulic analysis of the MED and independent soils sampling and testing.
The Soil Survey (1980) shows and describes the soil along the MED as dominantly a Heldt clay loam which is a clay soil formed from clay shale. This soil is characterized as deep, well drained, slowly permeable and having high water capacity. On steep slopes, like the ditch sidewalls, it has high erosion potential.
The geotechnical drilling and sampling conducted for Ayres (2004) confirmed this material as native clay (CL in accordance with the Unified Soil Classification (USC) system) with some sand, lying approximately 15’ thick over siltstone/claystone bedrock. Accordingly, the MED flow line upstream of Wilson would be expected to lie at an elevation approximately at the same level as weathered bedrock. While called out as bedrock, this material does not have the appearance of a “rock”; as its name implies, it is dense clay that weathers rather quickly to fine clay upon exposure to air, water and freeze/thaw conditions.
Soil samples taken of the MED banks and bed as part of the subject project (collected during the November 1, 2005 field visit) confirm the presence of this same clay soil type, CL in accordance with the USC. Soil sample test results are provided in the Terracon Soils Analysis which is attached. Weathered siltstone/claystone is commonly observed along the MED flow line in the form of dense, grey colored chips. The desiccated chips crush into very fine particles when pressured between the fingers. The bank sample and the bed sample both classify as clay with the bank sample having a much higher proportion of fine material. This material is available in sufficient quantity as a turbidity source for an indefinitely long time. Both samples have traces of sand and stone chips that are inadequate in quantity to result in an armored ditch bed. Accordingly, the stream bed will continue to degrade at a progressively slower rate, eventually reaching an equilibrium slope of flatter than 0.001. Bed material is likely the same material as the banks, with a significant amount of the finest material having been washed away by the flowing water, with weathered bedrock lying immediately below the loose bed. The settling time of this clay material is measured hours and days, versus minutes and hours. This means that using detention ponds to settle out enough of this suspended material from the MED water to have desired impact on water quality would require a long time period and large volumes. Both samples show a significant amount of the fine soil remaining in suspension after two days, indicating the possible presence of colloidal clays, which are not feasible to remove from water by gravitational settling.
The soil sample taken from Boedecker Reservoir bottom is coarser than the soil from either the MED bed or sidewalls, possibly indicating that the finer sediment in the Reservoir influent water passes through the Reservoir or is available in smaller quantities than from the MED downstream. This soil type is also a CL in accordance with the USC. Confirmation of the primary soil type in the area as a CL is also provided in the Boedecker Dam rehabilitation report (Tetra Tech, 2003).
Task 1.6: Topographic Surveying
Mariano Exchange Ditch (MED) System Assessment Project Task 1.6 - Conduct Topographic Surveying Based on the information gathered as part of Task 1.2 it was concluded that no additional field surveying was needed at this time. Adequate information was found to be available through the MED hydraulic analysis completed by Ayres Associates (Ayres, 2004). That information includes cross section surveys for the full reach at frequent intervals that adequately define the cross sections themselves as well as the longitudinal gradient of the MED. One comment on this information is that none of the cross sections show the several vertical or undercut banks which exist along the middle of the reach between the dam and Wilson Avenue. It suffices to simply recognize that such features exist even they do not show up on the survey. Several important conclusions that can be reached from evaluation of this information. The first is that the MED upstream of Wilson Avenue exists at a very flat slope (0.002 approximately), similar to other irrigation ditches, such that it is unlikely that significant vertical degradation is actively occurring. The MED downstream of Wilson Avenue has a steeper, but still flat slope (0.007 approximately) similar to natural streams in the area, such that it is likely that in the absence of natural armoring, some vertical degradation is occurring. This continuing vertical degradation was observed on at least one of the site inspections. The Ayres (2004) survey and the associated hydraulic analysis also confirms that the MED channel banks are generally higher than necessary and the channel conveyance greater than necessary at most locations for transmission of irrigation and drainage water. The banks exist at much steeper (generally 2:1 or steeper) than normal (4:1 or flatter) side slopes. The height and side slopes of the MED banks result in sections of MED which are unstable and have little cover, providing a source of sediment as described elsewhere. The inconsistency of the MED cross section geometry and high, steep banks are characteristics of an infrequently maintained and difficult to maintain ditch.
Task 1.7: Analysis
MEDS Project - Phase 1Key Initial Findings
Impact of the MED on the Big Thompson River
1 On 9/12/05, the MED added approximately 2.7 # TP/day to the Big Thompson River.2 According to historical data, there is a significant increase in TP in the river on days when the ditch is running.3 On 9/12/05, the MED added approximately 31 # TN/day to the Big Thompson River.4 On the one day when TN was measured upstream and downstream of the confluence (7/20/04), TN increased from 380 to 420 ug/l.5 On 9/12/05, the MED added approximately 8,500 # TSS/day to the Big Thompson River.6 TSS concentrations in the MED (~80-90 mg/l) are approximately twice as high as the river concentrations at M90 (~40 mg/l, 2000-2004 data)7 At M130, TSS concentrations are significantly higher than at M90 (mean = 480 mg/l, 2001-2004 data), pointing to other very large sources along the river between M90 and M130.8 The temperature of the BT river was warmer downstream of the ditch during the summers of 2002 and 2003.9 On the one day when turbidity was measured upstream and downstream of the confluence (8/11/02), the turbidity increased from 10 to 40 NTU.
10 There is no correlation between turbidity and TSS in the ditch based on 9/12/05 data.11 Impacts of the MED to aquatic life, recreation, agriculture, and water supply on the Big Thompson have not been quantified.
Characterization / Sources of These Constituents
1 Boedecker Reservoir is a significant source of turbidity, TP, and TSS to the MED.2 Cattail Reservoir appears to be a source of TN to the MED.3 There is a large source of TSS in the MED between Wilson Avenue and the mouth (almost doubles the concentration).4 Turbidity increases in the MED between Site 4 (~2,000 feet from the reservoir release) and the mouth by 20 NTU.5 The TSS in the MED is predominantly inorganic.6 The side walls of the ditch are unstable and failing in sections of the ditch.7 The grade of the ditch is flatter upstream of Wilson Avenue and little or no bed degradation is apparent. Downstream, particularly
behind the elementary school, the grade increases and more bed degradation occurs.8 Based on the information analyzed thus far, it appears that both the reservoir and the ditch are contributing
to the turbidity problem at the confluence with the BT River. It is hypothesized that very fine clay material onthe side walls of the ditch slough off and fall to the bottom of the ditch via block failures when the ditch isnot running. These blocks provide a ready source of fine clay to ditch flow, thus increasing the turbidity. The source(s) ofTSS in the ditch between Wilson Ave and the mouth have not been identified. Based on the one samplingevent, it appears that the ditch does not contribute phosphorus or nitrogen. The sources of turbidity and TSSin the reservoir have not been identified. Release concentrations of TP and TN are not unusual for a reservoir.
Other Key Findings
1 The current condition of the ditch presents a safety issue, both in terms of public safety and potential property damage.2 Additional testing will be needed to differentiate the reservoir from the ditch and to better characterize the sources.3 There are potential options to operate the MED system differently to reduce loadings to the BT River.
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1/1/2002 1/1/2003 1/1/2004 12/31/2004 1/1/2006
TP
(u
g/l)
VM40 U/S
VM30 D/S
On days when the MED is running, TP concentrations increasein the BT River.
