Prior to the construction of Camanche Dam, acid mine drainage from a closed copper mine, the Penn Mine northwest of Valley Springs, heavily polluted the Mokelumne River. EBMUD and the state's Central Valley Regional Water Quality Control Board attempted to solve the flow of acid mine drainage into the reservoir and river, but their efforts led higher concentrations of acid mine drainage and continued fish kills in the Mokelumne. After a series of lawsuits, EBMUD, and the state funded a $10 million remediation of the site.