Post-Fire Emergency Flood/Erosion Protection for the County of San Diego
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Nearly four years after the historic 2003 wildfires devastated San Diego County, strong, shifting Santa Ana wind conditions, combined with high temperatures, low humidity, and multiple years of drought combined to create the perfect conditions for fast spreading wildfires in 2007. The 2007 fire season saw approximately 500,000 acres burned within Southern California, with over 340,000 acres within San Diego County alone, destroying over 2,300 structures and several people losing their lives. With winter rains fast approaching, the County of San Diego faced the potential for devastating mudslides and debris flows that could inundate thousands of homes, close evacuation routes, and cause significant environmental damage. Using Geosyntec's 2003 Post-Fire hazard response as a model, personnel from the County and Geosyntec initiated an Emergency Flood / Erosion Protection Program that first assisted homeowners in protecting their property, then stabilized watersheds to reduce mudslides and debris flows.

Geosyntec's Scope of Services

Within four months, Geosyntec and County staff implemented an Emergency Flood/Erosion Protection Program on an historic scale. High risk areas were identified and prioritized to effectively utilize resources. Geosyntec performed hazard and impact assessments of hundreds of home sites and County road miles and identified 54 high-priority home sites (HPS) and 33 high priority road (HPR) sites. Erosion mitigation plans for HPS and HPR sites that included drawings, specifications, materials and cost estimates were prepared for each high priority site. Specifications were created to address the unique post-fire erosion conditions. Geosyntec trained County personnel on hazard identification and assessment, mitigation measures and conditions appropriate for deployment, and proper installation and field CQA during BMP stormwater control measure implementation. Geosyntec coordinated and oversaw hydraulic mulch application; trained California Conservation Corps crews on BMP implementation, and assisted with BMP implementation, and conducted follow-up surveys to identify maintenance requirements. County Park watersheds were assessed for potential impacts to adjacent properties. Geosyntec developed evacuation warning lists from ground and aerial reconnaissance. Geosyntec's long-standing relationships with FEMA and the Natural Resources Conservation Service aided us in obtaining funding for the mitigation measures through the Emergency Watershed Protection Program.

Notable Accomplishments

By using innovative design techniques and a strategic approach to prioritization, Geosyntec completed this massive project in less than four months. This rapid response proved to be instrumental in mitigating vulnerabilities, as demonstrated when several large storm events inundated the burned areas during the project's implementation phase and tested the resilience of the protective measures. Geosyntec's early identification of high priority sites and implementation of protective measures resulted in no homes in burned areas being damaged by mudslides or debris flows, and no evacuation routes being closed for a significant time during several large rainstorms. The efforts of the County and Geosyntec personnel on the 2007 Firestorm Emergency Flood/Erosion Protection Project were recognized with receipt of the "Award of Excellence" presented by the American Society of Civil Engineers San Diego Chapter.

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Project Summary

  • Location: San Diego, California, USA
  • Client: County of San Diego
  • Project Practice Areas: Contaminated Sites, Water and Natural Resources
  • Type of Facility: Urban Watershed
  • Services Provided: Post-Fire Emergency Erosion and Flood Control; Best Management Practice (BMP) Design; GIS and Database Management; Public and Regulatory Agency Interface
  • Type of Work: Flood and Erosion Protection
  • Governing Regulation: National Pollutant Discharge Elimination System (NPDES)