Background
Fugro West, Inc., is assisting the East Bay Municipal Utility District, Oakland, California, in developing a groundwater injection/extraction program on the East Bay Plain. The program goal is to provide drought year supply. During years when a surplus of water exists, it will be injected into an underground aquifer. The aquifer will serve as a water bank that can store a crucial supply until it is needed during an extended drought. Underground water storage is emerging as a cost-effective alternative to surface reservoirs.

Fugro's Role
Fugro's role in the EBMUD project is to help understand the local basin hydrogeology, aquifer parameters, and source and native ground water interactions that will be critical for project success. Maintaining high water quality standards are a requirement of the project.

The project initially evaluated the San Leandro/San Lorenzo basins the East Bay Plain area. Fugro:

• Studied the hydrogeology,
• Selected an appropriate site for the pilot project, and
• Reviewed how the supply would be incorporated into EBMUD's distribution system.

A critical component to the project was the design and construction of wells that will both inject and extract the water. A test injection/extraction well was drilled and water injected while the water level and quality in nearby wells is monitored. Maintaining high water quality standards are a requirement of the project.

Alternating cycles of injection and extraction were used to simulate full-scale operation of the 660-foot deep pilot well. Modes of operation included line flushing, injection, backflushing, and extraction. Water quality analysis was performed during all phases of the project.