San Francisquito Creek Joint Powers Authority
1231 Hoover Street
Menlo Park, Ca. 94025
September 29, 2010
Re: EIR Scoping Comments for San Francisquito Creek Flood Reduction Project
Thanks for your work on getting this critical project phase on a fast track to
implementation. We see the wisdom and unique potential for an effective flood
protection and ecosystem restoration project to occur early on in this lowest reach of San Francisquito Creek. We do request that with this fast tracking effort the project design will acknowledge and provide for the maximum flexibility and widest range of options for all future upstream flood protection and ecosystem restoration projects to occur and that the design will not limit future options related to these issues.
As the JPA and other watershed stakeholders have stated, it is critical to address this lowest reach of the creek first in order to facilitate imminent and planned flood protection and ecosystem restoration projects upstream, which may impacts this lowest reach. In addition, watershed stakeholders, including Stanford, have acknowledged that doing nothing at Searsville Dam is not an option and that significant changes at the dam will need to occur in the near future. Most of the options available for Searsville Dam, including lowering, removing, or letting the reservoir fill in, would return sediment transport from upstream of the dam to the mainstem of San Francisquito Creek. This situation could happen in as little as one more rainy season depending on erosion rates and flows.
For these reasons, we stress the importance that design plans must be made for these imminent future conditions and allow for maximum flexibility of options for the implementation of anticipated and discussed potential upstream projects, including those being investigated by the JPA. To not plan and design for these fast approaching, and different, conditions (which have already been studied and estimated) would be unacceptable, could compromise the effectiveness of the current project, and may severely limit future options, including those that might provide the highest level of safety, have the greatest ecosystem benefits, have the most funding and agency support, and are the most cost effective.
Below are comments for several issues we request be assessed and included in the project planning, design, and Draft EIR:
1) We request that this project, and all other future projects proposed by, or coordinated with, the JPA, provide the maximum possible stream channel carrying capacity for flows and sediment. We request that adequate conveyance of at least the 100-year flow event be achieved for the "worst case scenario" estimate of previously determined channel capacity changes predicated with the immanent filling or future lowering or removal of Searsville Dam upstream. This determination should include any additional data, such as climate change predications, that may further alter sediment transport, stream flows, or channel carrying capacity in the future. Being the lowest and keystone reach for future upstream project consideration we request that this reach be designed for flow and sediment transport conditions above and beyond what the combined worst case scenario of above consideration entails in order to maintain maximum flexibility for future upstream options to ensure the highest level of public safety and ecosystem restoration.
2) In addition to analyzing and designing flood reduction measures for this project, and future ones, based on high storm flows in the creek, we request that designs and documents include consideration and planning for flood safety reduction measures for already determined Dam Failure Inundation outcomes caused by the potential failure of the over-century-old Searsville Dam. San Mateo County produced this Dam Failure Inundation map for Searsville Dam, which would cause catastrophic damage and anticipated loss of life in much of the lower San Francisquito Creek watershed. It is not known what the current structural condition of the dam is because it has been 43 years since the Division of Safety of Dams (DSOD) has inspected the foundation, toe, and groins of the dam. Many earthquakes and several decades have past since this last foundation inspection. Stanford is responsible for coordinating this inspection that DSOD
has identified in the 2007 inspection report as a "prudent" measure that should be taken. As the dam and concrete continue to age and experience additional earthquakes the structural integrity is expected to be further reduced over time. The active San Andreas Fault run adjacent to Searsville Dam. The Dam Failure Inundation map and Division of Safety of Dams documents can be accessed in the FAQ section of our website.
3) As part of the ecosystem component of this project, we request that the project sets levees back as far as possible from the stream channel to enhance and expand the riparian zone, increase habitat complexity, maximize areas for overflow terraces and adjacent wetlands between the levees, and promote establishment of ecologically beneficial channel meandering and side channel habitat. The proposed project figure shows large areas (on the western side, adjacent to residents in East Palo Alto) that could be included within the levee set backs and allow for expansion of the riverine habitat and flood conveyance with increased overflow terraces. Pedestrian paths on the levee tops and trails within the levee's overflow terrace can also enhance recreation in these areas. These potential recreation areas should be prioritized for flood protection and ecosystem benefits with appropriate recreational opportunities established (such as bike paths, trails, and other activities that may be periodically inundated during major storms and flows on a decadal scale. The "floodwalls" identified in the proposed project figure are not described in detail, but well known and utilized bio-engineered levees and bank protection, that provide structural integrity and stated ecological benefits should be used throughout this project and concrete walls and other hardscaping techniques should be eliminated. By adequately setting levees back to the maximum extent possible and potentially adding additional conveyance features, the need for concrete floodwalls can and should be eliminated and more ecologically-minded biotechnical levees can be utilized. If this involves the expansion of the levees into adjacent athletic fields or golf course we request that this modest expansion occur instead of a more confined channel requiring concrete floodwalls. There may also be an opportunity, if needed, to buy a few key parcels from willing landowners along reaches just down from Highway 101 where the channel width is restricted.
4) I am very glad to see the proposed project include the removal of the northern levee and expansion of the San Francisquito Creek mouth and slough. As noted in the letter I sent to the newly formed JPA, almost ten years ago, it is essential that the study determine the most ecologically beneficial design in addition to the flood protection benefits already noted. We request that adequate analysis and measures are taken to provide the maximum ecological benefit of removing the northern levee and reconnecting the currently confined creek mouth with the newly proposed slough expansion to the north and connectivity to the San Francisco Bay. As seen elsewhere with levee breaching, careful study in needed to ensure success and address issues such as sediment deposition, water circulation, salinity interaction, use by non-native species, possible need for establishing a pilot channel, and maximizing benefits to rare and endangered wildlife, including anadromous fish rearing, acclimation between fresh and salt water, and adequate migratory attraction flows and depth between the creek and bay.
Director, Beyond Searsville Dam
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