When it rains heavily, Saw Mill Run rages.
Saw Mill Run is an urban stream with a lot of tributaries. The stream drains water from Carrick, Overbrook and other Pittsburgh neighborhoods, plus Mount Oliver, Castle Shannon and Bethel Park. It empties in the Ohio River around Pittsburgh’s Point. Along the way, the stream is a generally well-behaved secondary waterway. Except when it rains heavily.
The stream is 9 miles long – 22 miles when its tributaries, or the streams that flow into it, are included. The area that Saw Mill Run drains is its watershed. The watershed contains rain runoff, melting snow, other precipitation, the tributaries and groundwater underneath the surface.
The Saw Mill Run watershed has a lot of paved roads. The pavement keeps the water from flowing naturally into the ground. Instead, the water runs off, filling the tributaries, which flow into Saw Mill Run, which overflows its banks in a heavy rain. The water moves so fast that it tears apart the stream banks, causing trees to topple in and potentially undermining roads. The flooding damages houses.
More than two inches of rain fell in an hour in 2017. Saw Mill Run was particularly turbulent. It overflowed its banks and mixed with raw sewage. Streets were flooded. Homes were flooded. When the flooding subsided, debris and other pollution were carried back into the stream.
The Pittsburgh Water & Sewer Authority (PWSA) and other organizations manage the stormwater that causes the flooding. The PWSA organized a stormwater investigation team to respond to residents’ complaints about the flooding. The team gets a lot of calls.
Dredging and other work done by the U.S. Army Corps of Engineers has helped reduce the flooding.
One proposed solution for the flooding is for the City Of Pittsburgh to buy houses in the most flood-prone areas and tear them down. A natural open space would be landscaped to catch, channel and absorb rainfall. It could become a park for people to enjoy.
Watersheds of South Pittsburgh is studying the Saw Mill Run floodplain.
Saw Mill Run is named after an actual saw mill that was powered by the stream. The mill operated more than 250 years ago. Back then, the area was mostly meadows and forests that easily absorbed rain runoff. The mill was situated near the mouth of the stream – the place where it empties into the Ohio River. The mill cut lumber that was used to construct Fort Pitt – now Pittsburgh – after the British seized the area from the French, who had taken it from Native Americans. George Washington may have been familiar with the Saw Mill Run area.
Saw Mill Run is intertwined with industry and transportation.
Early in the 1800s, two gristmills operated on Saw Mill Run, according to the Carrick-Overbrook Historical Society. One mill was located at Fairhaven, now Overbrook. Gristmills grind grain into flour.
The Coal Hill Coal Railroad, which operated in the 1800s, transported coal from mines on Mt Washington and near Saw Mill Run. The railroad became part of the Pittsburgh and Castle Shannon Railroad. In the early 1900s, the right of way of the Pittsburgh and Castle Shannon Railroad was leased by Pittsburgh Railways, which used it to run trolley routes. Pittsburgh Railways was acquired by the Port Authority of Allegheny County. The Port Authority’s Light Rail system uses the former Pittsburgh and Castle Shannon Railroad right of way.
During the mid 1900s, Saw Mill Run “was considered a dead zone for aquatic life and a filthy, diseased waterway,” the Brookline Connection writes. The pollution was from runoff from sewers and abandoned coal mines, and litter and garbage.