I have been involved in Pitt’s Civil Engineering Senior Design Project program for more than a third of my life; initially as a mentor, then as program coordinator, and now as an advisor to the coordinator. The program serves as the Department’s Capstone event, the culmination of the students’ undergraduate careers. Each student functions as a member of a multi-disciplinary team challenged with the design of the solution of a significant near-real-world problem. One of the responsibilities of my current role is to suggest potential projects. This year one of the projects I suggested, the problem of abandoned mine drainage (AMD) in McLaughlin Run, is being studied by one of our teams.
Growing up in Bridgeville, I have been aware of pollution in Chartiers Creek by “mine acid”, domestic sewage, and industrial wastes most of my life. Learning that the Creek had been a pristine stream a century and a half ago, full of aquatic life, highlighted the tragedy that our society has produced here. The construction of the ALCOSAN treatment plant eliminated the domestic sewage; enactment of the Clean Water Act in 1972 plus the concurrent collapse of heavy industry in western Pennsylvania eliminated the industrial wastes. In recent years two highly successful projects – Wingfield Pines and Gladden — have removed well over half of the abandoned mine pollution; the remainder is still being discharged by a number of minor tributaries (including McLaughlin Run). Wingfield Pines is a large (six acres) passive remediation site with six settling ponds treating 1,500 gallons per minute (gpm) of discharge from the old Mayview mine. Located in Cecil Township, Gladden, an active remediation facility similar to a conventional water treatment plant, has converted Millers Run from a reddish-orange sewer into a lovely clear stream.
Among the remaining tributaries are four in the Bridgeville vicinity – Coal Pit Run, McLaughlin Run, Scrubgrass Run, and George’s Run (in Hope Hollow). Previous Senior Design efforts to remediate these streams with passive systems have been frustrated because of the lack of sufficient flat, open area; the Gladden problem was in this category. As a result of the success of its active system, I suggested we study one of these four streams as a candidate for an active solution using this approach.
The team we assembled has already made remarkable progress. I was pleased that they elected to focus on the McLaughlin Run option; it is probably the largest remaining source and is an eyesore as it passes through Bridgeville. They located the source behind a large building at 1029 McLaughlin Run Road, a building that Tom Grossi believes was the original garage for Bigi Bus Line. It is a large (twenty-four-inch diameter?) pipe located on the south side of the stream. Pressure to provide this flow is generated by water in a part of the abandoned Bridgeville mine high in Fryer’s Hill. They determined that its flow rate was 282 gallons per minute (gpm) and took samples of it for laboratory analysis, resulting in a determination that its iron content was thirty-five parts per million (ppm). This equates to about 120 #/day. This compares to 240 #/day at Wingfield Pines and 720 #/day at Gladden.
In their first progress report they presented an excellent summary of this specific problem. Abandoned mine drainage primarily produces two types of pollution — the conversion of the stream from alkaline to acid and the deposition of metals. When an abandoned mine fills up with water, it leaches iron sulfide (pyrite or “fool’s gold”) from the remaining rocks, which then dissolves into ferric and sulfate ions. When the effluent containing the ferric ions is exposed to air, the ions oxidize and produce the orange-red iron oxide particles that color our streams. In addition to being unsightly, the remaining stream has been deprived of oxygen, resulting in a level that will not support aquatic life. The team determined that the healthy McLaughlin Run upstream from the source had over ten ppm of oxygen, compared to about two ppm downstream. Although the AMD effluent was highly acidic, the remainder of the stream was sufficiently alkaline that the downstream portion was not acidic. For reference, the average flow rate of McLaughlin Run is about 8.2 cubic feet per second (cfs) which equates to about 4,000 gpm, much greater than the 282 gpm of AMD effluent.
The obvious resolution of this problem is to immediately oxidize the ferric ions and then allow sufficient time for the iron oxide particles to settle out before the effluent reaches Chartiers Creek. Wingfield Pines does this by spraying the effluent into the air, then allowing eight or ten hours for it to settle out in a series of large ponds. Gladden does it by introducing hydrogen peroxide as an oxidizer, then passing the effluent through a clarifier. Our team appears to be leaning toward the passive solution. They are considering pumping the effluent a mile and a half up McLaughlin Run to a location where there is sufficient room for a proper passive system, a perfectly acceptable solution for a senior design project. I don’t believe the site they have selected is available, however, but that it is irrelevant for this hypothetical project. The advantage of learning how to design a passive system is probably more valuable to them than merely applying their knowledge of design of a water treatment plant to this special case.
I continue to be impressed with the quality of the education Pitt is providing for our Civil and Environmental Engineers. The Department’s legacy is the growing number of effective real-world engineers that are making meaningful contributions to the construction and maintenance of our essential infrastructure. We rely on them for many of our basic needs, whether it be highways and bridges, buildings, water resources, or energy. I am intensely proud of the students we produced during my tenure and am confident our current crop will be equally productive.