PITTSBURGH (KDKA) — It’s never a good time to have a chemical spill on the Allegheny River, but especially, as we head into a holiday weekend that has boaters and swimmers enjoying the unofficial end to summer.

Although the DEP has a warning for the entire holiday weekend, it will only affect a section of the Allegheny.

A commercial detergent, known as Ethoxylated alcohol, that spilled into the Monongahela River from a plant in Newell Wednesday, is now the same chemical that dumped into the Allegheny River at the Allegheny Valley Joint Sewer Treatment Plant in Harmar.

“We’ve taken samples … to see what the water quality is,” Don Bialosky, with the DEP, said. “We’ve also worked with McCutcheon and asked them to put a water boom up around to contain any of the visible foam that’s there.”

McCutcheon Enterprises, the waste management company that cleaned up the Mon River spill, transported the detergent to the Allegheny Valley Joint Sewage Treatment Plant for disposal.

But some 2,600 gallons got into the Allegheny Friday afternoon.

“Unfortunately, the material that arrived was a little bit more concentrated than the sewage plant is used to,” Bialosky said. “It did upset the plant and some of the material’s leaving the plant untreated and that’s causing a fish kill.”

DEP estimates so far 20 to 30 fish are dead because this substance is toxic to aquatic life. It’s possibly harmful to humans in a concentrated form. Still, the DEP isn’t taking any chances.

“It should not harm humans, but we would really like people to stay away from it,” Bialosky continued. “They shouldn’t be swimming in this area. They should really try and stay away at this point. It will dissipate, dilute into the water and break down naturally.”

Again, the DEP would like swimmers and boaters to stay away from that section of the Allegheny through Labor Day.

The Pittsburgh Water and Sewer Authority says their treatment plant in Aspinwall closed its in-take valve, as a precaution. And it will stay closed for the next eight to 12 hours until the foam and chemical have cleared.

The PWSA assures none of this substance passed into Pittsburgh’s drinking water supply and the water is safe to drink.