• The Clinton River drains portions of four counties in southeast Michigan. The Clinton River Watershed drains 760 square miles and flows 83 miles from its headwaters to Lake St. Clair. Lake St. Clair connects Lake Huron to its north with Lake Erie to its south. The Michigan Department of Environmental Quality (MDEQ) began sampling intensively in the Clinton River due to the discovery of perfluorooctanesulfonic acid (PFOS) in the river at levels over the Rule 57 water quality standard of 11 ppt PFOS.