Sold in aerosol cans at the consumer level, it’s primarily composed of tetrachloroethylene (PERC). If the chemical sounds familiar, it should. It’s widely used in the dry- cleaning industry.

The manmade perc ponds are designed to help refill underground aquifers, which can hold more water than all 10 of the county’s reservoirs combined.

The two solvents, known as Perc and TCE, cause kidney cancer and other ailments, and have been the subject of years of controversy. By Hiroko Tabuchi The Environmental Protection Agency on Monday ...