Daywatch: Historical and environmental interests clash at Graue Mill

Good morning, Chicago.

Hydrologist Stephen McCracken has dedicated his career to conserving river ecosystems. But no project would consume more of his life than the historic Graue Mill dam.

In 2007, he surveyed the murky waters surrounding the Oak Brook structure. Within a few years, he was certain that the dam — adjacent to the 172-year-old mill — was the culprit of the river’s deteriorating ecosystem. It should have been a relatively simple project: Dozens of dams have been quietly...