On a gray day, just as the rain begins to fall, Roger Zylstra stops his red GMC Sierra pick-up truck on the side of the road and hops down into a ditch in Jasper County, Iowa. It takes two such stops before he unearths amid the tall weeds and grasses what he’s looking for.
“Here is one of the tiles,” he says, pointing to a pipe about six or eight inches in diameter. Water trickles from it into a culvert that runs under the road after flowing through a network of underground drainage lines below his farm field. “That’s where it outlets.”
Water like this is called runoff and it can contain harmful chemicals, such as nitrates from fertilizer that plants don’t absorb or excess pesticides. For years, contaminants like these have reached public waterways.