Mitigation Projects

Ridge Cut Giant Garter Snake Conservation Bank

The Ridge Cut Giant Garter Snake Conservation Bank is located in the Sacramento Valley Recovery Unit for the Giant Garter Snake Recovery Plan, within Yolo County, California. The Bank occupies 185.9 acres of a 2,400-acre property adjacent to the Colusa Basin Drainage Canal. The overall 2,400-acre property includes an established waterfowl production area and rice fields. The USGS found giant garter snakes in the Colusa Basin Drainage Canal in 2003, and found 40 individual snakes on the Ridge Cut property in 2004. The USGS has determined that the snakes interactively use the Colusa Basin Drainage Canal and adjacent rice fields.

Ridge Cut Giant Garter Snake Conservation Bank was established in 2010 and approved by the U.S. Fish and Wildlife Service (USFWS) to provide mitigation/compensation for actions that affect giant garter snake. The giant garter snake was listed as a federally threatened species on October 20, 1993, and listed as a state threatened species in 1971. The Bank is currently in the entitlement process with California Department of Fish and Wildlife (CDFW).

Construction and Performance

Giant Garter Snake
  • Construction of the site was completed in 2010 and resulted in the permanent protection of year-round habitat for the species. Ongoing GGS monitoring has occurred since Bank construction in 2010. Recent GGS surveys include visual encounter surveys for GGS conducted in 2013 and both visual surveys and trapping in 2014, 2015, 2016, and 2017. One GGS was observed and one was trapped during these surveys.
  • The Bank was designed as two independent but connected marsh structures. Each marsh structure contains open water habitat in the center, perennial marsh around the open water, and a sinuous perimeter of upland habitat. On the south-facing slopes, the transition between habitat types (i.e., open water, perennial marsh, and upland) is accomplished through construction of steep gradients (i.e., 2:1 slopes) to provide basking habitat immediately adjacent to the open water. The gradients between habitat types on the north-facing slopes is more gradual. Open water habitat is excavated to a depth sufficient to prevent infill from growth and siltation (i.e., greater than 5 feet) so that open water areas are maintained over time.
  • Upland habitat is designed primarily to provide basking areas and winter refugia for giant garter snakes. The upland areas also provide nesting cover for upland birds and waterfowl.

186 acres

Location: Yolo County, California

Mitigation Types

  • Giant Garter Snake

Service Area

The USFWS service area encompasses the Colusa Basin population and portions of the Yolo Basin, excluding areas of the legal delta, as shown in the service area map. The CDFW service area is the same except that it does not include the area south of Interstate Highway 80 in Yolo County, or any areas south of the Solano-Yolo County border, as shown in the service area map.

Approving Agencies

  • U.S. Fish & Wildlife Service

For additional information on the Ridge Cut Giant Garter Snake Conservation Bank, please contact Julie Maddox at (916) 435-3555 or