Restoration after sediment removal on East Washington Creek, Petaluma, California

Horizon assisted Sonoma Water to develop its Stream Maintenance Program (SMP). Under the SMP, sediment removal, vegetation removal and thinning, and bank stabilization activities are performed annually to maintain flow conveyance capacity in County flood control channels. Prior to the SMP, maintenance projects were permitted individually, which resulted in project uncertainty, delays, and high permitting costs. Horizon developed a comprehensive approach to achieve long-term (10-year and 15-year) permits with multiple regulatory agencies. Horizon also:

  • Prepared an award winning SMP Manual describing program activities, resources, and impact avoidance and minimization approaches.
  • Successfully obtained more than 35 interim permits from regulatory agencies for individual maintenance projects while the program was under development.
  • Developed a flexible mitigation program that uses on-site restoration and off-site watershed projects with partner agencies, landowners, and non-profit organizations.
  • Prepared and certified a Program EIR for CEQA compliance.
  • Conducted several technical studies including riparian vegetation mapping, wetlands inventory, cultural resources assessment, and sensitive species and habitat mapping to support permitting processes.
  • Developed treatment design templates for sediment removal, bank stabilization, and vegetation management activities.

Sonoma Water’s SMP won the 2009 Project Award of Excellence by the Floodplain Management Association (FMA) and the 2011 Outstanding Environmental Resource Document from the California Association of Environmental Professionals.

Since publication of the 2009 SMP Manual, Horizon has helped SCWA conduct sediment quality testing to comply with Regional Water Quality Control Board permit requirements and is currently updating the manual to reflect current maintenance approaches. In 2019, Horizon assisted Sonoma Water in updating and revising the SMP Manual.

Stream Maintenance Program, Manual, CEQA, and Permitting

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