The broken sewer main in Valley Forge National Historic Park was pumping out 5,000 gallons of raw sewage per minute before it was fixed.
Much of that sewage was flowing right into nearby Valley Creek, which in turn flows into the Schulykill River. That has raised concerns about the safety of both drinking water and area wildlife.
Aqua America told NBC that its water is pulled upstream of the spill, but Philadelphia Water Department officials told The Philadelphia Inquirer that they were on alert, and might need to shut down the Belmont or Queen Lane drinking-water intakes.
Valley Creek is designated by the Fish and Boat Commission as a Class A Wild Trout Fishery.
The break was in the Valley Forge Trunk Sewer Force Main at the intersection of Routes 23 and 252 in Upper Merion Township.
A new water main was brought in Wednesday morning, and crews were working on the repair.
The Valley Creek Trunk Sewer is operated by Easttown Township, East Whiteland Township, Malvern Borough, Tredyffrin Township, and Willistown Township.