The superfund site is at the southwest corner of town near Concord Mews, where the town meets Acton, Maynard, and Sudbury. This "Powder Mill" area has a long history of munitions manufacture stretching back to the colonial days. The contamination is thought to result from depleted uranium bullets manufactured for our last couple wars and the unscrupulous arms manufacturer that last owned the site - privatized profits, socialized cleanups. Any contamination that somehow missed clean up using federal bucks would naturally head downhill a short distance to the Assabet River. I wouldn't drink this river water or any well connected to it (you will notice that Concord has followed this very strategy). The closest Concord well (Second Division) is half a mile away on the other side of Thoreau Hills. Contamination of the water supply is doubtful unless the laws of physics are broken. Water quality is constantly monitored and published annually for all to see at any rate. You can get more info at
Concord, MA - Water Supply. FWIW, Concord water is by far the best municipal water I've tasted in the region and in my travels throughout the US. There's some terrible tasting water out there that must be treated up the wazoo.