In early 2000, it became apparent that Waukesha Water Utility (WWU), serving more than 71,000 people, could not continue to rely on its deep aquifer source for drinking water. The groundwater contains naturally occurring radium contamination at two to three times the EPA limit for radium. In addition, the water levels in the deep aquifer had dropped more than 350 feet because of restricted recharge and pumping was exceeding the rate of recharge. The depleted groundwater levels placed the aquifer in a protection zone. Compounding the problem, the dissolved salts in the deep aquifer water increased as drawdown increased. As such, the City of Waukesha faced both a water quality and water quantity problem. After several years of technical and scientific studies and analysis, Waukesha applied for a diversion of Lake Michigan water to the Great Lakes Compact Council. The application encompassed the technical evaluation of 14 water supply alternatives for safety, sustainability, and economic viability. Ultimately, the Great Lakes Compact Council affirmed and approved that the only reasonable water source for Waukesha was the Lake Michigan alternative. The alternative involves borrowing water from Lake Michigan and returning 100% after treatment to the Great Lakes Basin via the Root River, spurring additional water quality challenges and analyses. The challenge for the WWU is to keep the current water system in compliance by blending radium-removal treated deep aquifer water with treated water from shallow aquifer wells, while planning the transition of the entire system to Lake Michigan (surface) water. Aside from the engineering issues of designing a distribution system to move water out to Waukesha, several water quality challenges related to disinfection, corrosion, and groundwater/surface water chemistry differences must be evaluated before transitioning the distribution system to a new water source. In addition, Waukesha must ensure the returned water is treated before discharge to the Root River. The lessons learned by blending deep and shallow aquifer water, evaluating alternative water sources, and planning for the transition from ground water to surface water will be discussed.

Waukesha water:  Bridging the divide

255th National Meeting (2018)

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