A recent article by Nancy Allen published in The Daily Standard states that the source of pollution found near Prairie Creek is sewer water from a campground, not manure. 

Allen writes:

"Sewer water from a campground – not manure – was the source of an Aug. 26 pollution complaint to Mercer County soil and water officials. 

Soil and water board members reviewed the complaint from the south side of Grand Lake during their meeting Thursday.
Soil and Water Conservation District Technician Matt Heckler told board members the office received a complaint of black water and toilet paper coming from a manhole near the walking bridge at Prairie Creek along state Route 219. Upon visiting the site, soil and water officials found sewer water and toilet paper in a nearby ditch, he said…
… People with campers, mobile home trailers and manufactured homes at campgrounds around the lake can legally release sewer water into tile outlets built into the ground, SWCD Engineer Theresa Dirksen said. However, incompletely sealed tops on many of the tile outlets allow surface water to enter the sanitary sewer line during heavy rain events, she said…
… Many of the tile outlets viewed by SWCD officials at several campgrounds in the area had gaps around the pipes entering them. In addition, many unused tile outlets had no caps."