The Sauk River in the Upper Mississippi River Basin is listed as a fecal coliform impaired water. The 160 km river flows through areas densely populated with feedlots and dairies, however the river also flows through over a dozen lakes, which contain many lake homes with un-maintained septic systems. In an effort to better understand the nature of the river's impairment, a three part study was conducted. First, “hotspots” of E. coli contamination were determined by analyzing water from 17 sites along the river in September 2006, April 2007 and July 2007. Second, E. coli loading of sediment was determined at each site (July 2007). Third, as an inexpensive means of detecting leaking septic systems, fluorometry was used to determine the presence of optical brighteners from laundry detergents at each site (July 2007).