Chalfant Run and Thompson Run: A Tale of Two Watersheds

Located just east of Pittsburgh, the Chalfant Run and Thompson Run Watersheds lie in the suburbs of the bustling city. Home to over 35,000 residents, the watershed is prominent in the lives of many, whether they know it or not. 

While driving through the region, one can’t help but notice the countless bridges, tunnels, and walkways built around the many tributaries. What you cannot see, however, are the countless coal mines built underground. These mines, mostly left abandoned since the 1930s, spread throughout multiple coal beds. These coal beds, the Pittsburgh bed, Upper Freeport bed, and Lower Kittanning bed, spread throughout western Pennsylvania and neighboring states. 

With these abandoned mines come a multitude of environmental issues. As far as hydrologic issues, acid mine drainage is the main concern for environmentalists. Acid mine drainage, commonly referred to as AMD, is the discharge of groundwater from abandoned mines in the vicinity. AMD commonly decreases the pH of the tributary and introduces heavy metals into the water.

Below is an interactive map of the region. Slide the bar to see the mines pop up on the map! The pink shapes are abandoned mines, which indicate potential AMD affected areas.

Acid mine drainage is commonly measured for by focusing on a range of variables. Alone, these variables can give us the inclination that there is AMD. We treat them like a puzzle, piecing them together to get a larger picture of the watershed.

As previously stated, water samples were collected at strategic points throughout the watershed. With 19 sites in total, we were able to paint a general picture of the watershed for those analyzing the data. In the map below, the 19 sites are marked by the blue pins.

When viewing the map, the user can click on data points to view more information about each site. Popup menus will break down data by categorization, and further by variable. These data points are further analyzed in later sections.

Along with instream sampling points, flow was also monitored at four separate locations. Flow monitoring is useful when deciding on a proper way to remediate, or clean-up, a stream. With these measurements, we can gauge the scale of remediation needed for a specific site.

One way to understand complex data is to create a rating system. Many researchers use a report card of sorts, with grading scales from A-F like a typical educational institution would use to evaluate students. For the Chalfant Run/Thompson Run Watershed sites, I chose to do just that.

Below, we see the rating criteria by variable. These criteria are reported on the map that follows.

The map below corresponds to the criteria above, with the colors of points showing the overall (average) grade. Click on points to read about specific grades!

Water quality issues due to acid mine drainage are commonly handled through instream remediation or source control. Instream remediation methods typically are implemented at points of interest throughout a watershed, while source control methods are implemented where discharge from mines occurs.

Passive remediation tactics are the most applicable for the Chalfant Run/Thompson Run watershed. Passive treatments are economically efficient and require less maintenance than active systems. Systems have the ability to treat net acidic or net alkaline water and are able to remove a multitude of metals in the water. For the watershed, specifically at the four flow sites, a treatment system that focuses on reducing iron and sulfate concentration should be the main priority. 

There are a multitude of different passive treatment systems that can be applied to the site, but to narrow down to one there must be more data collected. The most promising remediation system candidate for this watershed is a passive anaerobic wetland/compost bioreactor. This method creates a biologically induced method of precipitating iron, removing sulfate, and increasing alkalinity. The diagram below depicts an anaerobic wetland/compost bioreactor system. 

This system of remediation can be implemented at many sites throughout the watershed. There is a displayed need for remediation of this kind at all points sampled.

Community members can contribute to restoration efforts in many ways. The best way to contribute is by reaching out to the Chalfant Run/Thompson Run Watershed Association, or by contacting myself, Andrew Clarke. 

This 21-page report was designed to give a detailed picture of the watershed and how AMD has impacted specific areas.