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HomeMy WebLinkAbout07/18/1988, 2 - COASTAL STREAMS DIVERSION AND STORAGE PROJECT MEETING DATE: �uIM01��p Vl�l� City Of San LUIS OBISPO Jul la 1988 ON ACOUNCIL AGENDA REPORT nW NUMBER r" From: Dave Romero Via: W.T.Hetland ', Prepared by: Hal Fones P.W.Director Utilities Manager Utilities Engineer SUBJECT: Coastal Streams Diversion and Storage Project By motion RECOMMENDATION: Direct Commission representatives to support the Coastal Stream Diversions and Storage Project; proceed with the EIR and to include a section on institutional and financial alternatives; and fund the additional work equally with the City of Morro Bay. BACKGROUND The concept of diverting eight coastal streams into the Whale Rock reservoir by using inflatable dams and the Whale Rock pipeline was the topic of a joint meeting of City Councils of Morro Bay and San Luis Obispo on June 26, 1986. As a result of that meeting a request was made of the Whale Rock Commission to conduct a study on the feasibility of the concept for enhancing our water resources. In August 1986, the Whale Rock Commission and the City of Morro Bay signed an agreement to share the expenses of the study, and in November 1986 executed a contract with Leedshill-Herkenhoff, Inc. to conduct the study on our behalf. The Phase I report was submitted to the Whale Rock Commission and the City of Morro Bay in April 1987. This report covered the Regulatory Requirements, Hydrologic Studies, Project Constraints, and Alternative Conceptual Plans. Work on the Phase II report was authorized to begin in April 1987. Staff engineers from the City of Morro Bay and the Whale Rock Commission reviewed the technical studies and Morro Bay proposed another alternative. In order to include the new "Alternate Day" plan for the Phase II report, additional work was necessary to expand the analysis done in the Phase I Report. At their meeting on October 9, 1987, the Whale Rock Commission agreed to a change order to expand the study for a total cost not to exceed $59,800 with the costs shared equally between the City of Morro Bay and the Whale Rock Commission. Many possible alternative diversion plans are possible and the Phase II report outlines some of the most promising concepts with their associated costs and anticipated yields. An executive summary of the report is attached. We are now at a point where it will be necessary to decide to proceed with the indicated steps for implementation. The Whale Rock Commission is asking water agencies to indicate their interest with the following questions. 1. Feasibility - Is the project feasible, based on the information presented, for your particular agency? The phase I and II portions of the study have demonstrated that this project is technically feasible for the City of San Luis Obispo. 41111QQ M111�1 city Of san pais OBISPO NiiS COUNCIL AGENDA REPORT Page 2 2. Participation - Is your agency willing to participate in the project, and if so, how much water would. your agency be interested in contracting for? Since the City of San Luis Obispo has storage rights in the Whale Rock Reservoir and is in need of additional supply, it would be appropriate for the City to participate in this project. The City's total need for additional resource could exceed the yield of this project. Therefore, the City should request as much water as possible taking into account the needs of other participating agencies. 3 . E I.R. - Should the Commission immediately proceed with the EIR and watershed survey, or should the institutional arrangements try to be resolved first? The instutional and financial arangements will be difficult to resolve and will take time. Additional EIR and watershed work needs to be done. To minimize financial risk in this project, the institutional arragements should be resolved first. On the other hand, concurrent work on the EIR and watershed study would help expedite the project. To minimize any time delays, the City should support moving ahead on the EIR. 4. Institutional and Financial Concerns - One of the key difficulties with this project is going to be developing the institutional arrangements and the financial considerations. These will be critical to the success of this project. Should the EIR be expanded to include an analysis of institutional arrangements and financial concerns? Preliminary discussions have indicated a wide difference in the potential institutional and financial arrangements for this project. There is merit in having a professional in this area evaluate the alternatives available. It would be appropriate for this to be part of the EIR. FINANCIAL IMPACT On June 27, 1988, Morro Bay City Council allocated $42,500 for funding 50 percent of the estimated cost of the EIR and the watershed survey. If the Whale Rock Commission funds the other 50 percent of these studies, they could be funded from the Whale Rock reserves. 1111 city of San Luis OBispo UQ; COUNCIL AGENDA REPORT Page 3 RECOMMENDATION Direct Commission representatives to support at the next Whale Rock Commission meeting the following: 1. The City of San Luis Obispo supports the Coastal Streams Diversion and Storage Project and is interested in obtaining as much water as possible taking into account the needs of other participating agencies. 2. The Commission should proceed with the EIR as soon as possible and it should include a section on alternative institutional and financial arrangements. 3 . Financing for the EIR and watershed work should be jointly done by the City of Morro Bay and the Whale Rock Commisssion, each sharing equally. These design study costs are to be reallocated as other agencies become participating members of this project. Approved: ty Admi istrative Officer City Att ey coastal2/hf4 jj cR —3 WLUM,U-MOOMHoFF.W_ EXECUTIVE SUMMARY The Coastal Streams Diversion and Storage Project (Coastal Streams Project) is a proposed water supply project involving eight streams in the Morro Bay area. The fundamental concept of the project is to capture excess runoff, which otherwise flows into the Pacific Ocean, by constructing low concrete diversion dams in the stream channels. The water would then be conveyed to Whale Rock Reservoir via the existing 30-inch diameter Whale Rock Conduit or new, additional pipelines. Alternatively, the water could be conveyed directly to a water treatment plant or other storage facilities. Because of the number of affected entities and existing contractual agree- ments, there are many complex political and institutional considerations which would have to be resolved before implementing the project. Most of these considerations involve the operation of the existing Whale Rock water supply system. The primary findings and conclusions derived during this feasibility study are summarized in the following paragraphs and in the tables at the end of this Executive Summary. Table ES-1 presents a summary of the project yield ' analyses and Table ES-2 shows unit water costs. 1. The average annual runoff expected from the eight Coastal Streams is approximately 15,000 to 18,000 acre-feet per year (AF/YR) . About 60 percent of this total runoff is from the two largest streams--Toro Creek and Morro Creek (which includes Little Morro Creek). These estimates are based on historical streamflow rec- ords gathered over the past 15-20 years and comparison to long- term hydrologic conditions. 3 2. The annual runoff in the Coastal Streams fluctuates widely depend- ing on rainfall patterns. Therefore, the quantity of water avail- able from a potential project on an annual basis will also fluctu- ate widely. The use of a storage facility such as Whale Rock Reservoir is essential to provide a sustained yield from the Coastal Streams Project. Alternatively, the Coastal Streams Project could be used as a direct diversion project to provide a supplemental source of water whenever water was available. 3. Due to regulatory constraints such as in-stream releases for upstream fish migration and hydraulic constraints such as existing pipeline capacity and maximum practical diversion rates, only a limited portion of the runoff could actually be diverted. For the diversion options analyzed in this study, quantities available for diversion ("potential diversions") ranged from about 22 to 40 percent of total average runoff. As discussed below, actual diversions based on reservoir operations studies will be lower than potential diversions to prevent excessive reservoir spill . i ES-1 WLEE=HILL-HERMHOFF,W_ 4. The alternative conceptual plans analyzed in this study involved i Toro Creek, Morro Creek, and Willow Creek. Toro Creek, which is I the second largest stream, can best utilize the existing Whale Rock Conduit to convey diversions to storage and would probably require a relatively low fish release of about 10 cfs or less. The Morro Creek Diversion was primarily selected due to the large volume of water available. If the existing Whale Rock Conduit I were being used by the Toro Creek Diversion, a costly parallel pipeline would be required to convey diversions. from Morro Creek to Whale Rock Reservoir. To eliminate the need for the costly additional pipeline, the Toro and Morro Creek Diversions could "share" the existing pipeline by alternating diversions on a daily basis between the two streams. This concept would presumably eliminate the need for a 10-15 cfs fish release since the natural flow of each stream would be pres- ent every other day. However, diversions would be limited to a total of 30 cfs due to the capacity of the existing Whale Rock Conduit. This "Alternate Day" diversion option was included in the feasibility study for comparison to the individual diversion options. The Willow Creek Diversion was selected because of its close proximity to Whale Rock Reservoir and the lack of required in- stream releases for fish migration. Although the yield is rela- tively small, the costs of implementing this alternative would also be relatively low. The conceptual plan formulated in this study assumed that diversions would be made directly into Whale Rock Reservoir with the use of a small pump station. 5. Based on potential diversions from the three streams, operations studies of Whale Rock Reservoir were conducted to determine the incremental reservoir yield added by the alternative plans for the Coastal Streams Project. Based on statistical analysis of the given hydrologic period, actual diversions over the 1944-86 study period were limited to about 51 to 63 percent of the potential diversions in order to minimize spills at the reservoir. However, prior to the critical year, aLl potential diversions were made and thus, the project yield has been maximized for the hydrologic period used for analysis. In the wet period following the criti- cal year (1967-86), diversions were restricted by "target stor- ages" to prevent excessive spilling of Coastal Streams diversions. Consequently, the operations studies indicate that only 13 to 24 percent of the total runoff would actually be diverted to Whale Rock Reservoir, depending on the diversion plan and operational philosophy. 6. The City of San Luis Obispo currently uses its share of Whale Rock Reservoir as dry season and drought backup for its Salinas Reser- voir supply. Therefore, the City's withdrawals are relatively small in normal and wet years but are quite large in dry years. ES-2 LUMDSHILL•HERKENHOFF, WC. Based on the current method of reservoir operation, the alterna- tive plans would add between 862 AF/YR (Toro Creek only) and 1782 AF/YR (Toro, Morro, and Willow Creeks) to the average reservoir yield resulting in total average reservoir yields (not safe yields) between 4999 and 5919 AF/YR. The corresponding dry year yield of the reservoir would increase by 898 AF/YR to 1818 AF/YR resulting in total dry year releases of 7818 to 8738 AF/YR. Because the annual reservoir withdrawals change drastically from year to year under existing operations, a true safe annual yield such as the 4400 AF/YR currently accepted for Whale Rock Reservoir cannot be computed under the current operational philosophy. Therefore, additional analyses were conducted for comparison to the currently accepted safe yield. These analyses indicated that the safe annual yield of Whale Rock Reservoir could be increased from current levels by 870 AF/YR (Toro Creek only) to 2346 AF/YR (Toro, Morro, and Willow Creeks) . The "Alternate Day" diversion option discussed above would increase the safe annual yield of the reservoir by about 1331 AF/YR. It must be noted that sufficient water demands must be present to realize the reservoir yields quoted above. From review of pro- jected supplemental water demands, sufficient demand will be present within 15 years to utilize the higher yield of the com- bined plan. Over the short term, sufficient demand should be available to utilize either the individual Toro or Morro Creek Diversions, the "Alternate Day" diversion option, or the Willow Creek Diversion. 7. Based on the conceptual plans and the reservoir operations stud- ies, estimated unit costs were developed for four alternative projects and three different financing scenarios. The four alter- natives and their respective unit costs are presented in Table ES-2. As indicated, the Toro Creek Diversion provides the lowest overall unit costs but the "Alternate Day" Diversion also provides a relatively low unit cost. 8. The .Coastal Streams Diversion and Storage Project is proposed to be a joint project between the City of Morro Bay and the Whale Rock Commission to increase the amount of yield from Whale Rock Reservoir. There appears to be a significant amount of additional yield available by taking Morro Bay's Coastal Streams water for which they have no storage and adding it to the Whale Rock Commis- sion's reservoir supply. A joint powers agreement between the City of Morro Bay, the Whale Rock Commission and other involved agencies will need to be devel- oped. Both the City of Morro Bay and the Whale Rock Commission will be providing important elements of this project. The City of Morro Bay will be providing the water (Morro Bay has filed for the water rights on the eight streams involved in this project) and has also. applied for low interest financing (a $5 million, 3.3% ES-3 lu LE®SHILL•HERKENHQFF.INC. interest loan for 20 years) for project construction. The Whale Rock Commission will be providing storage in Whale Rock Reservoir and will also be providing the existing pipeline and pumping facilities for transporting the water. This issue is a policy matter to be decided by mutual agreement of the Whale Rock Commission and participating agencies. There are numerous other complex institutional arrangements which would need to be resolved before implementation of the Coastal Streams Proj- ect. f733.sumj244 ES-4 oZ -7 Table ES-1 Coastal Streams Diversion and Storage Project siviPRY of PROJECT YIELD ANALYSIS DIVERSION PLAN Average Annual Ouantities ; Toro Morro Toro/Morro Creeks Toro, Morro and (acre-feet) ; Creek Creek Alternate Day Willow Creeks Runoff 1971-1986 Average 1/ ; 49262 69986 11.248 119774 1944-1986 Average 2/ ; 39098 59078 8,176 85559 Potential Diversions 3/ 1971-1986 Average ; 19684 29467 29436 4,493 1944-19% Average ; 19224 1,793 19771 3,266 % of Runoff ; 401. 35/. 22/. 381. CONSTANT DEMAND Actual Diversions 4/ 758 19099 1,112 29025 of R,Inoff ; 249. 2Z/. 14/. 24% of Potential Diversions ; 6Z/. 61% 63% 6Z/. Incremental Reservoir Yield 5/ ; 870 1,237 10331 29346 HIGH/LOW DEMAND Actual Diversions 4/ ; 75B 931 1,074 19667 % of Runoff ; 24% IEM 131. 191. % of Potential Diversions ; 6Z/. 52/. 61% 51 Incremental Reservoir Yield 5/ ; B62 19034 19254 11782 1/ Based on gaged record for Toro and Morro Creeks streamflows. 2/ Includes estimates for 1944-1970 period. 3/ Based on available runoff with hydraulic and regulatory constraints. 4/ Values are less than "Potential Diversions" over 1944-1986 period due to restrictions to reduce excess spills at the reservoir (see Section 6-1). 5/ Values are greater than "Actual Diversions" due to lower spills and lower ending storage. i Table ES-2 Coastal Streams Diversion and Storage Project SJTIARY OF WIT WATER COSTS WIT COST ALTERNATIVE ($/AF) TOTAL COST (1) TORO CREEK DIVERSION 170-210 $ 803,000 (2) MCS CREDO DIVERSION 430-710 $4,596,000 ' (3) TOROlMQRRO CREEKS ALTERNATE DAY DIVERSION 2W-340 . $ 2,083,000 (4) COMBINED TOM, 1"IQ�RO, AND WILLOW CREEKS 320-590 $ 6,257,000 i *;NM NNOUN p M n -•� -+ J $p. 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Prepare Construction Plans and Specifications 2/ (51009000-3009000) 9. Construct Project and Perform Testing 3/ 1/ Work can primarily be done in-house; outside legal costs were not estimated. 2/ Cost depends on specific alternative selection. 3/ Costs presented in Chapter 6.