Water Well Journal

December 2015

Water Well Journal

Issue link: http://read.dmtmag.com/i/608970

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Page 31 of 89

A brief look at aquifer storage and recovery (ASR) projects around the country reveal they are often large, complicated by source and receiving water quality issues, and in- volve a myriad of government, public, and private interests. For those reasons alone, ASR has a reputation for being expensive and has been mostly used by large municipal water systems. However, a small water utility dis- trict in Warren, Oregon, the McNulty Water People's Utility District (PUD), used a single well for ASR, and in so doing, increased its water system stor- age capacity by 600% for considerably less cost than the steel, above-ground reservoir it originally considered. The PUD, which is about 30 miles north of Portland, provides water for domestic and light commercial purposes to more than 2000 customers. Officials there decided an additional one million gallons of reserve storage was needed to satisfy excess system demand during the dry season, provide backup in case one of its wells went out of service, and assure a ready reserve for emergencies such as fire suppression. The PUD was ready to construct one or more above-ground reservoirs, but an interesting alternative seemed possible. It had drilled a routine water supply well into the regional aquifer a decade earlier that remained unusable. Testing showed the well could supply water at high transmissivity, but once drawn down, water levels took years to recover. The interesting thought was if the well couldn't recharge efficiently, per- haps it might be ideal for aquifer storage. Exploring the idea The idea was certainly attractive. Other wells in the PUD's system draw water from the same aquifer. Water from those wells could be injected during pe- riods of low demand and the resulting aquifer-to-aquifer transfer promises a minimum of chemical incompatibility. The PUD had infrastructure already in place to use the well water. It seemed a minor task to add plumbing and moni- toring for injection. The PUD also has a water right for the injection well since it was originally intended for use as a water supply well. As such, the Oregon ASR application process was an incre- ment—something in addition to but not supplanting rights otherwise held by the PUD. But the PUD was worried about geo- logical unknowns. Why does the well recharge so slowly? The nature of the barrier that restricts communication be- tween the regional aquifer and the zone tapped by the well is a mystery. All the other wells in the regional aquifer recharge very quickly. How much water could be stored is an apparent anomaly. The PUD's worries were not re- stricted to science. How rigorous would the state's regulatory requirements be? If the PUD was unable to afford addi- tional geologic characterization, would the regulators allow the project to progress? How far into the project could the PUD allow itself to venture without full knowledge of all the downstream project costs? Having to resolve an un- expected issue halfway into the project could easily catapult expenses to un- acceptable levels. An unsuccessful water supply well proves aquifer storage can be a key to success. By Bob Mansfield More than 6 million gallons of water can be stored under this 4-foot-high roof for a water utility in Warren, Oregon. Photo by John Borden. SECOND USE continues on page 30 WWJ December 2015 29 Twitter @WaterWellJournl

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