Did the foul contents of a porta-potty wipe out the 400-some fish that died in Mill Run this week?

That’s the angle Department of Environmental Resources scientists are most strongly considering. In fact, in what would be a great episode for The Discovery Channel’s “Dirty Jobs” series, DEP staffers made a trip to Powell Sanitation on Cussewago Road. Their task: Dip out some fluids of a used portable toilet and compare that chemical mix with the waters retrieved from the stream earlier in the week.

“We want to see if we can draw any parallels with the diluted sample (from Mill Run)” and the freshly dipped liquids of a returned tank, said DEP program manager Ricardo Gilson.

Though it might seem like an odd direction to some, “It’s all open,” said Gilson. “We never say never.” And, based on other evidence they’ve seen so far, a positive test result could seal the case for the local researchers.

An area of the creek that runs below North Street has been the main target. “We went back out again today (Friday) and are focusing on that area again, looking for more evidence,” Gilson added.

“That area” is a 1,000-yard stretch of Mill Run from the corner of Liberty and North streets down to Meadville Public Library, near North and North Main.

Anthony Matelock, DEP water quality specialist, carefully studied portions of the creek bed with Terry Crecaft, a waterways patrolman with Pennsylvania Fish and Boat Commission.

One suggestion was quickly ruled out. White residue found on rocks near Meadville Medical Center’s Mill Run Complex (the former Coca-Cola plant, was crossed off the list, Gilson said. Brandon Schuster, quality improvement administrative assistant at MMC, had noticed the frost-like coatings on Tuesday and alerted DEP and the Tribune.

Though the residue was not identified, it was not consistent with other evidence, such as stormwater studies, and was too far from what is now considered to be the problem area.

Gilson said it’s possible that someone dumped the contents of a portable toilet (either free-standing or in a recreation vehicle), spilling the fluid directly into the creek or into city pipelines by lifting a manhole cover or using a streetside drain.

Some of the covers protect access points to the city sanitary system, and those waters would be safely processed. But some go into the stormwater run-off system, and some of the stormwater goes into Mill Run.

Whatever method of dumping was used, “we were surprised that somebody would go to this extent” with their dirty water, Gilson said.

“People frequently discount a little stream like Mill Run as being nothing more than an open sewer. It just goes to show people that if we take care of things in our backyard, that’s still a nice little creek with nice things in it,” Gilson said. “So, that’s another objective (of making the Mill Run incident so well known), to let people know what a special stream this is.”

On Wednesday, Freda Tarbell, DEP community relations coordinator, expressed her agency’s bittersweet surprise that so many fish and so many species had been affected by the blue-green waters that had fouled Mill Run.