Aquifer Storage and Recovery (ASR) Demonstration Project
City of Tracy, California

West Yost is responsible for managing and directing technical work associated with the feasibility of implementing an aquifer storage and recovery (ASR) program for the City. This program involves the injection of treated surface water (when available during the winter months) into the groundwater basin for storage and later extraction during peak demand periods or dry years.

To determine the suitability of the groundwater basin for injection, storage, and recovery, West Yost conducted testing and analysis of the groundwater basin hydrogeologic and geochemical characteristics. West Yost also assisted the City in designing, cost constructing, and equipping Production Well No. 8 as an ASR well.

Based on formal regulatory approval by the California Regional Water Quality Control Board (CRWQCB), the ASR demonstration project is currently in operation for the short term and is providing temporary storage of up to 300 acre-feet of treated drinking water in the certified aquifer. The water will remain underground for a period of several months and will be extracted at various intervals during the subsequent months to determine the rate of degradation of disinfection by-products and other geochemical changes. The movement of the water will also be monitored using data collected from monitoring wells. All water that is injected will be pumped out using Production Well No. 8, and after testing, may be pumped into the water distribution system for use. West Yost is currently training City staff on properly injecting water and flushing the well, monitoring the injection and extraction processes, evaluating laboratory results, reporting to the CRWQCB, and preparing a final report.

ASR will greatly enhance the reliability of the City’s water supply, especially in drought conditions, by allowing surplus water in wet years to be stored for use during dry years.