The Pittsburgh Water and Sewer Authority and the U.S. Army Corps of Engineers have agreed to share the $1.2 million cost of a design plan for green infrastructure that would divert 17 million gallons of stormwater annually from combined water and sewer pipes under Negley Run Road.
The project site is one of several that have been identified since 2014 where stormwater can be taken out of the system to reduce or eliminate flooding on and around Washington Boulevard.
PWSA and the Army Corps will focus on the slope of Negley Run Road. At the top, water and sewer lines have been separated as part of new housing construction in Larimer and East Liberty. The intention would be to grab the baton from the housing component to run the next leg of infrastructure upgrades down the slope.
“Those pipes going downhill are carrying all the sewage and water to connect to larger pipes under Washington Boulevard all the way to the Alcosan interceptor at the river,” said James Stitt, PWSA’s sustainability manager.
“We are looking for a design that would not only remedy the issue of excessive water but do it in a way that would be environmentally healthy,” said Carol Vernon, a spokesman for the Army Corps.
With separated water and sewer lines, stormwater could be diverted by letting it cross Negley Run Road via a culvert in order to join the natural stream, Negley Run. The stream is underground now, but the plan would be to free it so that it can course visibly downhill.
The next phase would identify what to do with stormwater once it is on the plain.
The stream could be rechanneled to meander to slow its course, or a holding tank underground could capture excess water and release it slowly into the ground, Mr. Stitt said. Wetland features would do the same thing but with cattails and other water-filtering plants.
Any or all of those remedies are possible, “anything we can do to increase the capacity,” Mr. Stitt said.
The Army Corps will bear 75 percent of the cost for a conceptual design. The installation cost will be determined when the design options are evaluated, likely late next summer, Mr. Stitt said.
For future work, he said, PWSA will make another request of the Army Corps and possibly Alcosan.
One remediation project has been done and several more are being planned. These projects have involved the Penn State Center, the city’s Department of Public Works, the Western Pennsylvania Conservancy and the Larimer Consensus Group, among others.
The first Negley Run green infrastructure and stormwater diversion project was completed last June — a 1,100-foot bioswale that took two years to complete from inception.
It was designed to capture 600,000 gallons running down the pavement of Negley Run Road each year.
Diana Nelson Jones: djones@post-gazette.com or 412-263-1626.
First Published: December 10, 2017, 9:46 p.m.
