BOARD AGENDA MEMORANDUM
SUBJECT:
Title
Coyote Creek Flood Risk Reduction Ad Hoc Committee’s Recommendations and Associated Staff Analysis from the Committee’s October 5, 2017, Meeting.
End
RECOMMENDATION:
Recommendation
A. Receive a report from the Coyote Creek Flood Risk Reduction Ad Hoc Committee and staff analysis.
B. Provide direction to staff to operate the Anderson Reservoir system through the winter of 2017/2018 following the 40% exceedance rule curve that was recommended by the Coyote Creek Flood Risk Reduction Ad Hoc Committee at the October 5, 2017 meeting to reduce the risk of flooding along Coyote Creek and provide adequate water supply while balancing other beneficial uses.
Body
SUMMARY:
On October 5, 2017, the Coyote Creek Flood Risk Reduction Ad Hoc Committee received information and discussed alternatives for providing short-term flood risk reduction on Coyote Creek.
Staff Analysis:
Information on Anderson Dam reservoir operation options for short-term flood risk reduction on Coyote Creek was provided to the Committee on August 31 and October 5, 2017 for discussion. The meeting agendas and supporting materials are attached. Two alternatives were considered; pump over and reduced reservoir storage.
The pump-over option would install a large-scale pumping system using the existing spillway to increase the release of incoming flows into Anderson Reservoir and thereby maintain storage goals. The pump-over option has significant risks, costs, and would require a lengthy environmental review and permitting effort, and is unlikely to be implementable for at least the next four to five winters.
Similar results can be achieved by operating the reservoir at a reduced elevation, meaning at a lower storage level. The reduced reservoir storage would increase the available flood storage volume behind the dam during the winter season.
Both options would reduce the risk of flooding for the downstream communities. If there is a below average rainfall year, the reduced reservoir storage could result in reduction of water supply, water supply reliability, and cold water releases to Coyote Creek for fisheries, but it is immediately implementable. Given the current water supply conditions, it is recommended that staff be directed to operate the Anderson Reservoir system through the winter of 2017/2018 following the 40% exceedance rule curve to reduce the risk of flooding along Coyote Creek and provide adequate water supply while balancing other beneficial uses.
FINANCIAL IMPACT:
The Office of the Clerk of the Board has budgeted funds to support the business meetings of the Board’s Advisory Committees for Fiscal Year 2017-2018. Under the specific water supply conditions that apply to the winter of 2017/2018, the proposed operation of the Anderson Reservoir system is not anticipated to increase the annual operating costs in fiscal year 2018.
CEQA:
The annual operation of the reservoirs does not constitute a project under CEQA because it does not have a potential for resulting in direct or reasonably foreseeable indirect physical change in the environment. Implementation of the pump over alternative would require CEQA before installation of the pumps.
ATTACHMENTS:
Attachment 1: 083117 CCFRR Ad Hoc Committee Agenda and Materials
Attachment 2: 100517 CCFRR Ad Hoc Committee Agenda and Materials
UNCLASSIFIED MANAGER:
Manager
Kurt Arends, (408) 630-2284