Aquifer Recharge, Storage, and Recovery - Southwest Hydrology ...

ASR in Roseville:Navigating Water Quality IssuesChristian E. Petersen – MWH Americas Inc. and Kenneth Glotzbach – City of RosevilleThe City of Roseville, in theCentral Valley of Californianear Sacramento, is studyingthe feasibility of aquifer storage andrecovery (ASR) to maintain water supplyreliability during dry periods. An ASRpilot and demonstration project hasbeen underway since 2004 to improveunderstanding of the hydrogeologicfactors affecting well flow and waterquality, identify and address regulatoryconcerns, and evaluate operationalconsiderations associated with augmentingRoseville’s water supply with ASR.Water SupplyThe city’s current annual surface watersupply of 66,000 acre-feet is AmericanRiver water diverted from Folsom Lake.The city maintains a contract entitlementwith the U.S. Bureau of Reclamationfor 32,000 acre-feet per year for CentralValley Project supplies and contracts withlocal agencies for the remaining 34,000acre-feet per year, some of which isavailable only in normal and wet years.Roseville may also purchase Section 215water, released by Reclamation fromFolsom Lake in excess of the entitlementsLonger-term testingwas needed tounderstand the fateand transport of DBPsin the subsurface.and rights of downstream users when it isavailable, but has not done so yet. FolsomLake water treated to potable standards atRoseville’s water treatment plant is beingused for the ASR testing and will alsobe the supply for the long-term project.A county policy prevents Rosevillefrom relying on groundwater as asource of supply. Roseville intends tooperate its ASR program as a seasonalstorage program, but would alsolike to retain some water in longertermstorage as protection againstdroughts. ASR is allowed by the countybecause it does not result in a net takefrom the basin: the volume of waterextracted will not exceed the volumeinjected and stored in the aquifer.Testing ASR FeasibilityASR testing at Roseville is beingcompleted in two phases. First, a shorttermpilot test was conducted in 2004using the Diamond Creek well, whichwas installed as a dual-purpose injectionrecoverywell. It is screened from 310to 450 feet below ground surface in aconfined zone of the target aquifer, theMehrten Formation (see figure, top right),a coarse-grained sand, gravel, and cobbleof volcanic origin deposited in a fluvialenvironment. Three existing wells wereused to monitor water level and waterquality in the aquifer during the test.Results from the short-term test indicatedthat ASR is feasible in Roseville, butthat longer-term testing was neededto understand the fate and transportof disinfection byproducts (DBPs) inthe subsurface. Therefore, Phase IIdemonstration testing began in November2005 and was to be completed in May2008. Water quality and water levelsare again being monitored in the fourwells. No problems have yet beenencountered regarding well pluggingassociated with solids accumulation orgeochemical precipitation in the well.Enter the Regulatory EnvironmentAlthough drinking-quality water mightappear to be ideal to store underground,California’s water quality regulators sawit differently. The State Water ResourcesControl Board oversees nine regional30 • May/June 2008 • Southwest Hydrology