GSI is helping the City of Woodland, California, develop its aquifer storage and recovery (ASR) system.


The City is preparing to convert its primary potable water supply source from groundwater to treated surface water diverted from the Sacramento River. During periods of lower demand (winter months), unused treated surface water will be recharged into the aquifer for storage using a series of specially-designed ASR wells. During the summer, when there are flow restrictions on the Sacramento River, the recharged water will be extracted, dosed with hypochlorite solution, and conveyed to the City’s distribution system. The objective of the project is to store treated surface water to improve the reliability of summer pumping and improve the quality of pumped water.

GSI’s Solution

Working with Carollo Engineers, GSI is providing hydrogeologic services for design, installation, and testing of two ASR wells, two sets of nested monitoring wells, a core hole, and two well abandonments. GSI is also testing an existing ASR well to evaluate water quality mixing and compatibility. A future phase of the project will include pilot testing and possible expansion of the ASR program.

Project Highlights

  • GSI staff have designed, permitted, and supervised the construction and testing of the ASR and monitoring wells.
  • Each well was drilled to approximately 500 feet and was tested at rates from 1,500 to 3,000 gpm (gallons per minute).
  • When treated surface water is available, GSI will plan and implement an interim injection program after the wells are drilled and tested. Temporary injection equipment will be installed as the aboveground pumping and injection system is being designed to begin developing the target storage volume.
  • After the wellhead improvements are completed, the well should be able to immediately begin recovery of high quality water.
  • Another benefit of the program is to improve the quality of water being produced by the wells because native groundwater is high in arsenic, hexavalent chromium, and nitrate.