Matilija Dam Ecosystem Restoration Project
Project Specifications
Client: Ventura County
Location: Ventura County
Services: Environmental Review & Permitting, Biological Resources, Geospatial Sciences & Data Analysis
In 2001, the Ventura County Public Works Agency – Watershed Protection (Watershed Protection or VCPWA – WP) initiated the Matilija Dam Ecosystem Restoration Study as a joint effort between the VCPWA - WP and U.S. Army Corps of Engineers (USACE) to develop a project resulting in the removal of the Matilija Dam.
In support of a feasibility study being prepared by the USACE, Aspen provided various environmental services, including NEPA and CEQA compliance documentation. The dam was constructed in 1948 to store water for agriculture and to provide flood protection. Because of sedimentation that has occurred behind the dam, it currently has very little water storage capacity and virtually no flood control function. The purpose of the feasibility study was to evaluate alternatives for removing the dam in order to allow passage for steelhead trout and allow sediment to move downstream to replenish sand on area beaches. The project also involved removal of Arundo donax along Matilija Creek and the main stem of the Ventura River.
Aspen prepared a joint EIS/EIR for the Matilija Dam Ecosystem Restoration Project under our task order contract with the USACE. The EIS/EIR examined seven project alternatives that were comprised of alternative strategies for removal of the dam and the disposal of sediment that has accumulated behind the dam. The project also entailed downstream improvements to maintain the flood-carrying capacity of the river and prevent deterioration of drinking water quality. The various benefits of the project are also discussed in the EIS/EIR, including eliminating of barriers to steelhead passage, restoring the natural hydrologic and sediment transport regime, improving riparian habitat quality, eradicating non-native plant and animal species, and restoring Matilija Canyon to a more natural, pre-dam condition. The project objectives include aquatic and terrestrial habitat improvement along Matilija Creek and the Ventura River, restoration of natural sediment transport processes, and return to a viable and abundant run of steelhead trout. The joint Environmental Impact Statement/Environmental Impact Report (EIS/EIR) was certified in 2004.
In addition to preparing the EIS/EIR, Aspen prepared GIS vegetation mapping for the Ventura River corridor and Matilija Creek through a combination of aerial photo interpretation and field surveys. Vegetation communities were delineated as field drawn polygons onto geo-referenced and ortho-rectified aerial image field maps that were developed with GIS software. Field-collected vegetation community information was digitized into GIS and used to generate vegetation community mosaics. Aspen also supported the project’s Environmental Working Group (EWG) in evaluating and scoring the quality of existing habitat and projecting habitat conditions under a future without-project scenario and for each project alternative.
In June 2017, the VCPWA - WP received funding to implement the Matilija Dam Removal 65% Design Planning Project. The updated plan to remove Matilija Dam incorporates new information garnered from recent dam removal projects as well as modifications to downstream infrastructure. The VCPWA - WP has determined that preparation of a subsequent EIR (SEIR) is warranted to evaluate the revised Project. The SEIR will provide a complete and objective analysis of the revised scheme for dam removal and will function as a Program EIR that can be used in the environmental review of subsequent component development projects during implementation of MDERP. In addition to analyzing the environmental effects of MDERP at a programmatic level, the SEIR will also provide a project-specific analysis of the environmental effects associated with the development of five MDERP components, which would likely be some of the first projects developed under the MDERP, including: the Camino Cielo Bridge Replacement; the Robles Diversion Structure Rebuild; Meiners Oaks Levee; Live Oak Acres Levee; and Casitas Springs Levee.