Delta Ecosystem Enhancement Advance Mitigation

A riparian forest is part of the Cosumnes floodplain mitigation site where DWR purchased bulk credits in Thornton, Calif.

A riparian forest is part of the Cosumnes floodplain mitigation site where DWR purchased bulk credits in Thornton, Calif.

Since 1990, DWR has invested over $80 million to create 3,300 acres of habitat enhancement and mitigation sites in the Delta. DWR has run the Delta Levee Program (DLP) for nearly 30 years through grant funds with Delta-located Reclamation Districts (RDs) to maintain or improve non-project (i.e., not regulated by the Army Corps of Engineers) levees.

The California Water Code and California Department of Fish and Wildlife (CDFW) regulates and sanctions projects that impact habitat must mitigate. Historically, mitigation was accomplished through small, dispersed “postage stamp” mitigation sites that proved to be too small to have biological integrity. Replacing habitat loss with higher quality habitat for plants and animals is a better biological-functioning option. Therefore, DWR created the Bulk Credit Program and is in the planning stages of creating advanced mitigation on Twitchell Island.

The Bulk Credit Program enables the RD’s to acquire mitigation credits at a cost-savings in addition to saving tax-payer money and ensures replacement of impacted habitat with mature native vegetation. The Bulk Credit Program is the result of Jersey Island RD partnering with Cosumnes Floodplain Mitigation Bank owned by Westervelt Ecological Services. DWR purchased roughly ~90 acres (credits) of Riparian Forest, Scrub-shrub, and Freshwater Marsh habitat. In addition to 4,000 linear feet of Shaded Riverine Aquatic habitat. Buying in bulk resulted in saving California $1,000,000 or more compared to retail prices.

Currently, DLP-specific mitigation credits are only available at the Cosumnes Floodplain Mitigation Bank. However, a limited number of these credits designated for mitigating RD habitat impacts remain. Therefore, DWR proposed the creation of an advanced mitigation site on Twitchell Island located in Sacramento County.

The DWR owned property will provide additional high-quality and cost-effective mitigation credits for DLP participants. The Twitchell Island Mitigation Enhancement Site (TIMES) is currently in the planning stage and will break ground in fall 2021. After establishment, the TIMES project will contribute 110 advanced mitigation acres and 70 enhancement acres to DLP participants.