Twitchell Reservoir spans the borders of Santa Barbara County and San Luis Obispo County. Constructed in the late 1950s, the man‐made lake supplies water and flood protection to the Santa Maria Valley. Twitchell had a capacity of 240,300‐acre feet with a maximum water elevation of 651.5 feet when built by United States Bureau of Reclamation in 1958 (per USBR website). The dam and reservoir provide flood control and water conservation; the Central Coast of California only receives significant amounts of rainfall during the winter, this area averaging 14 inches (360 mm) per year. The water is stored in the reservoir during big winter storms and released as quickly as possible while still allowing it to percolate into the soil and recharge the groundwater; this means that the reservoir is usually far from full. It is estimated that the project increases recharge by 20,000‐acre ft (25,000,000 m3) annually.

Along with Dam stabilization and removal of sediment from the Reservoir basin, the scope of the project encompasses mitigation of influent-contaminated sediments, water contamination, and preemptively addresses the deposit of eroding soils from upstream drainages to mitigate future adverse effects for the Reservoir and damage to the Dam that sustains it. Global Clean Water, Inc. (GCW) has contracted with both WSRC and MSL to address functions in each of the four (or more) phases of the Twitchell project which is expected to require 7-10 years to complete.

The Twitchell Dam and Reservoir site is the first of several California locations where these contract services may be performed by MSL. Two additional projects are currently in queue.