Adam Babetski, TribLive
Wed, Jul 22, 2026 • 05:01 AM
View the article on TribLive
The Parkway East’s new $95 million Commercial Street Bridge crosses more than the road it is named for. The span also stretches over Nine Mile Run, a rare urban stream that flows from Frick Park to the Monongahela River.
Because the 20-foot-wide stream sits directly beside the construction site and has a long history of pollution from the nearby Parkway East, PennDOT built a temporary 200-foot-long gravel causeway for construction vehicles. The structure, supported by large drainage pipes, allowed heavy equipment to cross the stream while minimizing damage to its banks and waterway.
John Myler, PennDOT’s District 11 senior assistant construction manager, said the causeway ultimately caused less harm to Nine Mile Run than repeatedly driving heavy construction vehicles through or alongside the stream.
PennDOT is working with UpstreamPgh, a local environmental organization, to make sure that Nine Mile Run stays as clean as possible during construction. Upstream’s Plan/Build director, Aaron Birdy, said the partnership was essential to help preserve a waterway that has made a “serious comeback” over the years.
“It ensures that the stream continues to rebound and remain healthy,” he said.
Going with the flow
Nine Mile Run was once an infamous “open sewer” — trickling through concrete pipes in sections — with low water flow, heavy contaminants and little to no aquatic life, Birdy said. Multiple studies from the late 1990s found that the upper reaches of the stream were totally absent of fish.
Upstream debuted in 2001 as the Nine Mile Run Watershed Association, which focused on restoring and protecting the stream. The organization has since diversified into conserving other local watersheds like Negley Run and advocating for clean drinking water.
One of Upstream’s largest projects remains its $7.7 million Nine Mile Run Aquatic Ecosystem Restoration, which it completed with city agencies and the Army Corps of Engineers in 2006. Together, the groups removed the pipes, deepened the stream to help it flow regularly and added rocks and native plants.
Aquatic life has since returned to Nine Mile Run. Upstream has observed 47 different species of fish inhabiting its waters, including rosyface shiners and emerald darters.
Upstream maintains two sampling sites to monitor Nine Mile Run’s condition above the parkway’s Commercial Street Bridge in Frick Park and a third downstream of the bridge in Duck Hollow, near the mouth of the Monongahela. A 2023 study by Brady Porter, an associate professor of biology at Duquesne University, showed significantly more species of fish near the downstream station compared to the Frick Park locations.
With that in mind, Upstream will keep a close eye on the downstream sampling site following the Commercial Street Bridge project, although Birdy expects any pollution to have cleared up by the time they take their next set of monthly samples in August.
“Streams kind of naturally clean themselves as they continue to flow,” he said.
PennDOT also plans to monitor the stream for the next year, Myler said.
Fighting pollution
Under Section 206 of the federal Water Resources Development Act, PennDOT had to work with the Corps of Engineers to restore Nine Mile Run to its previous condition following the Commercial Street Bridge replacement.
PennDOT was able to get one key change approved through a permitting process: Nine Mile Run will have a “rain garden,” or a shallow depression near the stream, that absorbs polluted runoff from Parkway East, like road salt, before it can seep into the stream.
“We’re hopeful that with this rain garden, that at least reduces some of the salt,” Birdy said.
The old Commercial Street Bridge’s drains would previously dump stormwater and runoff next to its footings, where it could flow into Nine Mile Run untreated, Myler said. PennDOT has also set up a temporary “filter sock” around the construction site to hold in contaminants, he said.
“Obviously, some debris did fall in the stream during the demolition, but we can’t prevent that,” he said.
Birdy agreed that some kind of pollution entering the stream was unavoidable, since it runs through a construction site near a major highway. However, he preferred a carefully planned project with clearly defined environmental impacts to an incident like the Fern Hollow Bridge, which had to be demolished on short notice after it collapsed in January 2022.
Myler said PennDOT plans to begin restoring Nine Mile Run later this year.
Contractors will use excavators to take out the pipes and strengthen the embankments with stones and wetland plants. They will also restore the in-stream rock vanes that protect against erosion, according to PennDOT spokeswoman Nicole Haney.
Birdy expects workers will be off the site by 2028.
“When PennDOT’s done, that section of Nine Mile Run will actually — theoretically — be the best section because it’s the most recently restored and regraded,” he said.
