PS Well Inside In the Central Valley aquifer system near Modesto, California, the USGS found that agricultural and urban development have enabled uranium to move from sediments to water in the upper part of the aquifer. This contaminated water drained down a public-supply well and entered the lower aquifer when it was not pumping. When pumping resumed, contaminant concentrations were temporarily elevated in water pumped from the well. As a result of USGS findings, public-supply well managers have changed their pumping schedule, which has reduced the amount of contaminated water pumped from the well.

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