Most of you are aware by now there is an issue of combined sewer overflows (CSOs) polluting Nine Mile Run. During wet weather, our watershed’s aging combined sewer systems do not have the capacity to handle both stormwater and sewage so they overflow into Nine Mile Run, introducing pathogens, trash, and other pollutants to the stream. We have actively worked to correct this issue through green stormwater infrastructure (GSI) interventions in the upper watershed over the last 14 years, including installing rain barrels and rain gardens and planting over 900 street trees.
Despite all of this effort, however, we still have degraded water quality during and after wet weather. When we developed our 2013-15 Strategic Plan there was one main goal: to reduce the flow of stormwater and sewage into Nine Mile Run.
We understood to achieve this goal we would need to install GSI facilities capable of capturing large quantities of stormwater before it enters the combined sewer system. In 2014, we worked with Matt Graham of Landbase Systems to identify areas in the watershed that have high amounts of stormwater flowing into curb inlets and eventually overflowing into Nine Mile Run. Through detailed analysis, he identified an area in the Homewood neighborhood of Pittsburgh, which is actually outside of the watershed, but is part of the Nine Mile Run sewershed, that contributes over 25 million gallons of stormwater and sewerage overflow to the stream annually during wet weather events.
In case you aren’t familiar, a sewershed is simply a drainage area determined by the curbs, storm drains, pipes, and outfalls that all drain to a common outlet (e.g., Nine Mile Run). It doesn’t match perfectly with the Nine Mile Run watershed boundary because sewersheds often cross the boundaries of watersheds that existed before urbanization.
The Rosedale Runoff Reduction Project (RRRP) is a holistic sustainable stormwater project with the goal to remove all 25 million gallons of overflow entering the stream. We will achieve this by constructing 3 large GSI sites, 40 stormwater management tree pits, 200 Hydra rain containers, and 10 rain gardens.
In October 2014, we were awarded $150,000 from PA Department of Community and Economic Development (DCED) Commonwealth Financing Authority (CFA) Watershed Restoration and Protection Program to construct one of the GSI sites. And most recently in January, we received notification that we were awarded $236,175 from the PA Department of Environmental Protection (DEP) Growing Greener Program to construct a second site and install 200 Hydras. Both of these grant awards will allow us to implement the first phase of the RRRP, which proposes to remove 7 million gallons of annual runoff from the combined sewer system.
Stay tuned for proposed plans, details, schedule of implementation, and outreach events related to the RRRP!