OSCODA – Verdant on a late summer evening, Clark’s Marsh, an old bend in the Au Sable River, is a fine spot for a walk, and the river is a fine spot to hook a trout. That natural beauty drew Arnie Leriche to this place.

When Leriche retired from the U.S. Environmental Protection Agency, he moved with his partner to Oscoda, the town just downstream from the marsh, with the idea that he would spend his work-free years fishing the clear waters of northern Michigan.

Trouble is, the marsh is just downstream from the former Wurtsmith Air Force Base, where toxic PFAS chemicals have been leaking into groundwater for decades from a field that was formerly used for firefighting training. The groundwater, tainted by foams used to put out the fires, seeped into the marsh, then into the river, and on down the watershed, even into Lake Huron. A few years ago, the Michigan Department of Community Health issued a warning to anglers: Do not eat the fish from the marsh.

Leriche, knowing a bit about pollutants from his years at the EPA, began to worry. Tests showed chemical concentrations in pumpkinseed and bluegill fish to be more than 15 times higher than state standards.