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HomeMy WebLinkAboutItem 12b - Santa Anita Dam Stormwater Flood Management & SeismicUpdate on Santa Anita Dam Stormwater Flood Management & Seismic Strengthening Project March 5, 2019 Page 1 of 4 DATE: March 5, 2019 TO: Honorable Mayor and City Council FROM: Tom Tait, Public Works Services Director By: Jacquelyn Mercado, Management Analyst SUBJECT: REPORT, DISCUSSION AND DIRECTION REGARDING THE LOS ANGELES COUNTY FLOOD CONTROL DISTRICT’S SANTA ANITA DAM STORMWATER FLOOD MANAGEMENT & SEISMIC STRENGTHENING PROJECT Recommendation: Provide Direction SUMMARY In 2012, the City Council entered into a cooperative agreement with the Los Angeles County Flood Control District (“County”), the City of Arcadia, the City of Sierra Madre, and the Raymond Basin Management Board for the Santa Anita Dam Stormwater Flood Management and Seismic Strengthening Project (“Project”). At the February 19, 2019, City Council meeting, Mayor Pro Tem Verlato requested that the City Manager provide a discussion item at an upcoming City Council meeting regarding an update on the Project. Specifically, Mayor Pro Tem Verlato is concerned with the lack of stormwater capture and spreading in the Santa Anita Spreading Grounds. The County has missed a vital opportunity during recent heavy rain storms to capture stormwater run-off through the Santa Anita watershed in order to fill local groundwater basins. It is recommended that the City Council provide direction in sending a letter to the County Board of Supervisors requesting an update and the reasons for delay in completing the Santa Anita Spreading Grounds portion of the Project. DISCUSSION The East Raymond Basin Water Resources Program was developed in 2005 as a part of the Water System Reliability Program study conducted through the Army Corps of Engineers to find ways to increase water storage and production in the East Raymond Basin. As a result of this study, four projects were identified that would increase ground Update on Santa Anita Dam Stormwater Flood Management & Seismic Strengthening Project March 5, 2019 Page 2 of 4 water storage in the East Raymond Basin through retention and infiltration of stormwater run-off from the Santa Anita watershed. The Cities of Arcadia and Sierra Madre are the only groundwater producers in the East Raymond Basin. Over the last 10 years, groundwater levels in the East Raymond Basin have been in a steady decline. This is mostly due to below average rainfall and a State mandated water level restriction on the Santa Anita Dam (“Dam”) because the spill way on the Dam does not meet current seismic requirements. This has restricted how much water can be held behind the Dam until the County completes their remediation project to address the seismic deficiency. Approximately 20% of Arcadia’s annual water system demands are met by wells in the East Raymond Basin. Groundwater in the East Raymond Basin is primarily from stormwater runoff captured and infiltrated in spreading basins. The East Raymond Basin Water Resources Program identified the potential to maximize groundwater recharge in the East Raymond Basin. The Project will modify four existing facilities along the Santa Anita Wash:  Santa Anita Dam  Santa Anita Spreading Grounds  Santa Anita Headworks  Santa Anita Debris Dam While each component on its own provides benefits, it is through their linkages and synergies that the benef its are optimized to meet the overall Project goals and objectives. In addition to the Santa Anita Wash’s primary function of flood control, the Santa Anita Flood Control System has the capability of capturing local stormwater for the benefit of recharge in the East Raymond Basin. This system averages 2,135 acre- feet of recharged water each year. The Project is anticipated to increase the amount of recharged water to the East Raymond Basin by 518 acre feet per year. Recognizing that the cost to repair the four major water facilities was beyond individual local agency budget limitations, the Cooperative Agreement establish ed mutual understanding between the County, the City of Arcadia, the City of Sierra Madre, and the Raymond Basin Management Board to move forward with the improvements and to collectively fund the costs of the projects . The total cost for the Project is estimated to be $52 million with half of the cost being funded by a Proposition 1-E Grant that was awarded to the County. The awarded grant requires a 50% match. The County is funding a majority of the match for the Project and requested under the Cooperative Agreement that the affected agencies fund the remaining part of the match up to 10%. The distributed matching fund costs were based on how the project affected each agency. The City of Arcadia paid a total contribution of $864,126 for the Project. A copy of the Cooperative Agreement is attached. Update on Santa Anita Dam Stormwater Flood Management & Seismic Strengthening Project March 5, 2019 Page 3 of 4 The Public Works Services Department (“PWSD”) recently contacted the County requesting an update on the Project, but more specifically the status on completion of the Santa Anita Spreading Grounds portion of the Project. The spreading grounds portion of the Project was broken up into two phases. The first phase was completed in October 2009, with the second phase is expected to be completed in Spring 2019. This will include the final item of installing a control system for the rubber dam, which in this case, is a bladder that lifts a plate to direct flows to the spreading grounds . An updated Project description sent by the County is attached. The PWSD stressed the importance of actively getting water to the spreading grounds and on February 21, 2019, the County responded by providing pictures of water being released into the spreading grounds under a temporary method until the Project is completed. Update on Santa Anita Dam Stormwater Flood Management & Seismic Strengthening Project March 5, 2019 Page 4 of 4 ENVIRONMENTAL ANALYSIS The proposed action does not constitute a project under the California Environmental Quality Act (“CEQA”), and it can be seen with certainty that it will have no impact on the environment. Thus, this matter is exempt under CEQA. FISCAL IMPACT In Fiscal Year 2012-13 the City of Arcadia paid $695,310 from the Capital Improvement Water Fund budget for the Santa Anita Dam Stormwater Flood Management and Seismic Strengthening Project. The remaining City share of $168,816 was paid in Fiscal Year 2013-14. RECOMMENDATION It is recommended that the City Council provide direction in sending a letter to the County Board of Supervisors requesting an update and the reasons for delay in completing the Santa Anita Spreading Grounds portion of the Santa Anita Dam Stormwater Flood Management and Seismic Strengthening Project. Attachments: Los Angeles County Project Description Update Project Cooperative Agreement The Dam does not meet current State standards for withstanding a maximum credible earthquake (MCE) or safety passing a probable maximum flood (PMF). To address seismic safely concerns and safely pass PMF: xInstalled a new concrete outlet tower riser to pass flows above elevation 1230 feet. Completed in October 2012 for $2M. xConstruct a new spillway to safety pass the Probable Maximum Flood (PFM); xRe-armor downstream canyon walls & dam toe; xInstall new valves and upgrade hoist system – a new platform for the hoist has been constructed; xReplace the garage/storage and housing for a new back-up generator; xReplace the potable water system. Status: Construction phase—The process to cut the new spillway notch has begun. Start Date: April 2018, Anticipated Finish Date: August 2020. Estimated Construction Cost: $27.2M. SANTA ANITA DAM The Debris Basin does not meet DSOD standards for seismic safety. Remediation of the seismic deficiencies at the Debris Basin will consist of the following improvements: xReplace outlet tower, and rehabilitate the outlet pipe; xReconstruct the spillway, and buttress the spillway walls. Status: Design almost completed. Working to develop a design plan to meet USACE PMF (hydraulics) requirements for the proposed spillway. Working to obtain USACE 404 and 408 permits, which in- cludes conducting an Independent External Peer Review. Anticipated Start Date: 2020, Anticipated Finish Date: 2021. Con- struction Cost: $12M. The Headworks primarily consists of an earthen levee, a bypass channel with a radial gate, and manual diversion gates. The Headworks becomes impacted when the Dam outflow exceeds 300 cfs. Rehabilitation of the headworks structure will include: xReplace earthen levee with concrete weir structure to be able to pass flows up to 6800 cfs and also withstand overtopping; xConstruct new culvert bridge to Arcadia Wilderness Park to also pass flows up to 6800 cfs and withstand overtopping; xInstall new automated diversion gates; xInstall new control systems. Status: The scope of work has been revised. We anticipate having the design plans approved by early 2020. Anticipated Start Date: 2020, Anticipated Finish Date: 2021. Construction Cost: $7M. SANTA ANITA DEBRIS DAM SANTA ANITA HEADWORKS The Santa Anita Stormwater Flood Management and Seismic Strengthening Project (Project) will modify four existing facilities along Santa Anita Wash. These facilities are the Santa Anita Dam (Dam), the Santa Anita Debris Dam (Debris Dam), the Santa Anita Headworks (Headworks), and the Santa Anita Spreading Grounds (Spreading Grounds). While each component on its own provides benefits, it is through their linkages and synergies that the benefits are optimized to meet the overall Project goals and objectives. The project will be constructed in phases. This project will improve District facilities to better manage stormwater runoff from the Santa Anita Canyon watershed and achieve the following goals: 1. Reduced flood damage to the downstream communities; 2. Increase recharge of local groundwater basin; and 3. Improve public safety by remediating seismic safety issues at the Dam and the Debris Dam. Project Description The Santa Anita Stormwater Flood Management and Seismic Strengthening Project has an approximate estimated cost of $52,500,000. COST COST SHARING x City of Arcadia: $864,126 xCity of Sierra Madre: $900,938 xRaymond Basin Management Board: $234,936 xState Proposition 1E Grant: $20M xLos Angeles County Department of Public Works: $30,500,000 The Spreading Grounds enlargement and enhancement will be completed in two phases. Phase 1 (completed) xConstruct three new basins, enlarge the remaining basins, and modify basin 2 & the canal; xRaise levee elevations. Start Date: June 2009, Finish Date: Oct 2009. Construction Cost: $622K. Phase 2 (Substantially completed) xLine the eastside canal; xDeepen and expand basins and replace inter-basin structures; xInstall automated electrical gates & control systems. Status: Construction of the project is substantially completed including the installation of the rub- ber dam in the outlet system. Control system (telemetry) for the new rubber dam is currently be- ing worked on. We are also evaluating alternative means to transport water to the spreading grounds. Construction Start Date: Summer 2016, Anticipated Finish Date: Spring 2019. Construction Cost: $3.7M SANTA ANITA SPREADING GROUNDS Updated Feb 2019 SANTA ANITA DAM SANTA ANITA SPREADING GROUNDS SANTA ANITA HEADWORKS SANTA ANITA DEBRIS BASIN FLOW PATH FLOW PATH FLOW PATH SIERRA MADRE SPREADING GROUNDS FLOW PATH