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Flood Control

 

 

March 2011

The City of Petaluma has participated in the National Flood Insurance Program (NFIP) since 1983. The decision to participate followed the devastating 1982 flood, the largest flood in Petaluma's history, which caused an estimated $28 million in damage. The NFIP, which is managed by the Federal Emergency Management Agency (FEMA), provides subsidized flood insurance in flood prone areas of our community. The NFIP requires flood insurance for structures located in Special Flood Hazard Areas (SFHA) in communities that participate in the NFIP. In addition, most lenders require flood insurance as a condition to mortgaging a home within a SFHA. The SFHA defines the land within the regulatory floodplain of a community subject to a 1 percent or greater chance of flooding in any given year, commonly referred to as the 100-year flood. The City currently operates under FEMA's Flood Insurance Rate Maps (FIRM) dated 2008, created in a digital format from the 1989 maps drawn following our initiation into the NFIP Program.

Following the 1986 flood in Petaluma, the City began intensive work efforts with the U.S. Army Corps of Engineers on a project to reduce the potential for flooding in Petaluma. In 1994, the Corps completed a Section 205 Detailed Project Report for Flood Control that identified a plan to provide a 100-year level of protection for the Payran Reach area of the community. The plan included 3,600 linear feet of channel widening and floodwalls, pump stations, two vehicular bridge replacements, and two railroad bridge replacements. In 1996, the City and the Corps signed the Project Cooperative Agreement to begin work on the Project.

Between 1997 and 2008, nearly $40 million in improvements on the Petaluma River Flood Control Project (Project) were completed, including replacement of the Lakeville and Payran Street bridges, construction of the U-shaped channel and trapezoidal channel (between Lynch Creek confluence with the Petaluma River downstream to below Lakeville Street), removal and replacement of the mainline railroad bridge at Lakeville Street, construction of the approaches to the mainline railroad bridge, removal of the railroad spur bridge downstream of Lakeville Street, and construction of the industry railroad spur (constructed rather than build a second railroad bridge over the River). Essentially all physical features of the project have been completed except for the Sheetpile Wall and Channel Excavation Project in the vicinity of the now removed industrial railroad bridge. In addition, once the last of the physical improvements are completed, approval of the Operations and Maintenance (O&M) Manual will wrap up the overall Corps project. Even though the Corps Project is not yet finished, the completed portions operated per design during the December 2005-January 2006 flood event.

The City began the work to submit a map revision request to FEMA during the surface water research and analysis undertaken as part of the General Plan 2025 preparation. Following the adoption of the new General Plan in May 2008, work was completed on the model run and analysis for the submission of the remapping application. The City submitted a formal application requesting a map revision to FEMA in November 2008. FEMA provided preliminary comments in June and July, 2009, to which the City promptly responded. We received comments on the submittal from FEMA and are performing final map review and engineering for final submittal.

The design values of CV and skew are based on the average of 167 gage records with 5280 station years. This data is summarized in the file "New CV & SK D 2009.xls" and "Consolidated Daily Rain 2009.xls", both dated June 13, 2009 (Insert links to published data provided by Jim Goodridge, P.E., State Climatologist (retired)). Frequency precipitation calculations are provided in the file "G03 E20 D Petaluma FS.xls" dated December 29, 2009.

The City is now preparing a revised floodplain and floodway map and expect to begin the required community outreach effort to solicit public participation in the remapping process later this spring (2011). FEMA estimates the remapping approval process to take at least –30 – 36 months following submittal of the application (begun in November 2008).

&M Manuals. The City is currently discussing funding balances with the Corps. Pending resolution of the disagreement on cost-sharing balances, it is not likely to achieve project completion for two years. In addition, the impacts associated with Hurricane Katrina have caused the Corps to amend their sheetpile wall certification standards, which may cause additional analysis on our existing sheetpile floodwalls.

Given the length of time it may take to complete the Petaluma River Flood Control Project, the City is initiating the work to obtain an 'A99' designation for the Payran Reach area. Zone A99 applies to areas where flood control projects under construction have achieved "adequate progress" but may not be completed. Section 61.12 of Title 44 – Emergency Management and Assistance regulations stipulates that "Where the Administrator determines that a community has made adequate progress on the construction of a flood protection system involving Federal funds which will significantly limit the area of special flood hazards, the applicable risk premium rates for any property, located within a special flood hazard area intended to be protected directly by such system will be those risk premium rates which would be applicable when the system is completed". Under this program, the City may request that the areas protected by the Project in the SFHA in FEMA's FIRM maps be designated as Zone A99.

The Zone A99 designation could provide relief in flood insurance rates for residents in these areas now protected by the Project that are technically still "under construction" because the Corps has not completed all aspects of the Project. Residents in Zone A99 areas are still subject to the mandatory flood insurance requirements of the NFIP, but their rates are determined assuming the flood protection work is complete.

In summary, revising FEMA's FIRM maps will require final submittal of the City's map revision request, submittal of the A99 documentation if determined to be appropriate, FEMA approval and acceptance of the revision request and the A99 documentation, FEMA preparation of revised FIRM maps, City review and comment on the revised FIRM maps, public outreach to receive comments on the revised maps, then issuance of final maps by FEMA.

 

Contact Information

Director, Public Works and Utilities
Dan St. John, F.ASCE
202 N. McDowell Blvd
Petaluma, CA 94954
Phone: 707-778-4546
Fax: 707.206.6034
Email: dstjohn@ci.petaluma.ca.us

Administrative Offices
202 North McDowell Blvd.
Petaluma, CA 94954
Phone: 707.778.4546
Fax: 707.206.6034
Email: publicworks@ci.petaluma.ca.us
Hours: 8:00 A.M. - 5:00 P.M.
Monday - Friday

Utility Billing
11 English Street
Petaluma, CA 94952
Phone: 707.778.4350
Hours: 8:00 A.M. - 5:00 P.M.
Monday Thursday

Water, Sewer, or Storm Water Emergency
Phone: 707.778.4546

Water Conservation
Phone: 707.778.4507
Email: conservation@ci.petaluma.ca.us

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Field Office
202 N. McDowell
Petaluma, CA 94954
Phone: 707.776.3777