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HomeMy WebLinkAbout1997-10-06 City Council (25)City of Palo Alto City Manager’s Report TO:HONORABLE CITY COUNCIL FROM:CITY MANAGER DEPARTMENT: PUBLIC WORKS DATE:OCTOBER 6, 1997 CMR:419:97 SUBJECT:INFORMATIONAL REPORT ON THE SANTA CLARA VALLEY WATER DISTRICT’S MATADERO/BARRON CREEK FLOOD CONTROL PROJECT This report conveys information on recent developments concerning the Santa Clara Valley Water District’s (District) Matadero/Barron Creek flood control project. No Council action is required. BACKGROUND In March 1996, staff provided updated information to Council on the Federal Emergency Management Agency’s (FEMA) Special Flood Hazard Areas (SFHA) in Palo Alto (CMR: 183:96). The report included information on the status of the Santa Clara Valley Water District’s (District) flood control program in Palo Alto and an estimate of the number of properties that would be removed from the SFHA as a result of the channel improvements. An important component of the District’s program is the Matadero/Barron Creek flood control project. The fmal phase of the Matader0/Barron Creek flood dontrol project was completed in July 1996. The project, implemented in five separate construction phases over an eight-year period, was designed to protect approximately 5,900 flood-prone properties from flooding for up to the one percent flood1. Of this total, approximately 200 properties were to be removed from the SFHA on FEMA’s Flood Insurance Rate Map (see attached map). The remaining 5,700 properties either remain in the SFHA because they continue to be subject to saltwater flooding or were never included in the SFHA because they were subject to freshwater flooding less than one foot in depth. In order to Officially remove the 200 properties from the SFHA, the District is .required to apply to FEMA for a Letter of Map Revision (LOMR). The LOMR application ~The one percent flood has a one percent chance of occurring in any given year. It is sometimes referred to as the 100-year flood, because it is the flood that would be equaled or exceeded on an average of one time every one hundred years, measured over a long time period. CMR:419:97 Page 1 of 3 consists of maps, calculations, and other background information documenting that the channel improvements will provide protection from the one percent flood. DISCUSSION Upon completion of the flood control improvements in July 1996, District staff began preparation of its LOMR application to FEMA and expected to submit it in June 1997. District representatives have recently informed staffthat they have identified an error in the design of the Matadero/Ba~ron Creek flood control project (at the Matadero Creek and Louis Road bridge structure) that will prevent it from submitting a LOMR application to FEMA at this time. District staff will notify its Board of Directors of this issue at the October 7 Board meeting. As a courtesy, District staff will provide City staffwith a copy of its staff report. Since the District’s report was not fmalized prior to assembly of the Council packet, it will be provided at Council Members’ places on Monday night. Discovery of a design error in the flood control project has several implications for Palo Alto residents and businesses. First of all, the 200 properties in the SFHA that were expected to be removed will remain in the SFHA. District staff estimates a one and a half to two year delay in obtaining the LOMR required to remove these properties from the SFHA. As a result, property owners will continue to be required to carry flood insurance on their property if it is mortgaged, at an annual cost of $500 or more. The second impact of the design error is that there are a substantial number of properties that are not, in fact, protected against the one percent .flood. District staff have determined that, under current conditions, residents along Barron Creek have protection against the one percent (100-year) flood, but that Matadero Creek residents have only two percent (50-year) flood protection. Furthermore, the current conditions could induce flooding of properties that were not subject to flooding prior to construction of the flood control project. In its report, District staffprovides its Board with a list of alternative interim measures that could be implemented to mitigate the impacts of the design error and recommends a preferred alternative. The alternative recommended by District staff is to partially block the intake structure of the Barron diversion culvert to allow it to accept a maximum flow of only 300 cubic feet per second (vs. 600 cubic feet per second per the original design). This alternative will result in one percent (100-year) flood protection for Matadero Creek ¯ properties and five percent (20-year) flood protection for Barton Creek properties. The five percent (20-year) level of protection for Barron Creek properties is higher than pre-project conditions (20 percent/5-year protection), but lower than current conditions (one percent/100-year protection). The recommended alternative was selected by District staff because it eliminates the condition of causing flooding in new areas, provides improved flood protection to all properties when compared with pre-project conditions, and minimizes the total number of properties at risk of flooding. The District staff recommendation also includes provisions for conducting District-hosted public meetings in the affected neighborhoods to present information on the flood control project design error, interim CMR:419:97 Page 2 of 3 measures to be implemented, and status of the LOMR application. City staffwill attend the meetings. District staff will proceed based upon direction given by the District Board at its October 7, 1997 meeting. It is expected that interim measures will be implemented and public meetings will be conducted in late October. Staff will attend the October 7 District Board meeting and then return to Council with updated information once it is available from the District. FISCAL IMPACT This report has no fiscal impacts to the City. ENVIRONMENTAL ASSESSMENT An environmental assessment is not required for this informational report. ATTACHMENTS Areas to be eliminated from the Special Flood Hazard Area as a result of the Matadero/Barron Creek flood control project PREPARED BY: Joe Teresi, Senior Engineer DEPARTMENT HEAD REVIEW: GLENN S. Director of Works CITY MANAGER APPROVAL: City Manager Stan Williams, Santa Clara Valley Water DistriCt Kay Whitlock, Santa Clara Valley Water District Dave Chesterman, Santa Clara Valley Water District Randy Talley, Santa Clara Valley Water District Gary Uenaka, Santa Clara Valley Water District Susan Frank, Palo Alto Chamber of Commerce Will Beckett, Barron Park Association Kristen Johnson, Ventura Neighborhood Association Cole Richmond, Chestnut-Wilton Homeowners Association Debbie Mytels, Midtown Residents Association CMR:419:97 Page 3 of 3 Areas to be eliminated from the Special Flood Hazard Area as a result of the Matadero/Barron Creek flood control project Polo Altc Flood Basin ~Areas to be eliminated from Special, Flood Hazard Area Scale00.5 1 2 Miles AB14901o