The alkaline discharge near Thomas Mills, which has come to be known as Rock Tunnel, continued to be a constant problem as far as water quality was concerned.  Fortunately, for the creek and its recreational users, the site which has tainted the South Fork for so many years, was remediated during the summer of 1992 through the networking efforts of the Stonycreek- Conemaugh River Improvement Project (SCRIP) and cooperative efforts of the Somerset County Conservation District and Lion Mining. A passive treatment system consisting of hold ponds and connecting trenches were installed which has essentially eliminated the last major source of mine drainage in to the South Fork. (ref;http://www.mltu.org/Fisheries/bens_creek.htm)

The Rock Tunnel Site, associated with the abandoned Hillman Mine near the village of Thomas Mills , was the first site chosen for remediation by SCRIP in 1992 and was re-engineered in 2002, referred to as The Enhanced Treatment Project. 

Rock Tunnel site has one of the largest abandoned mine flows in the Upper Conemaugh drainage, discharging up to 3,500 gallons per minute of mine drainage. The Hillman Mine was a "D" seam coal mine but did not produce acid because the mine had a limestone floor. The mine does cause major pollution, however, because it has a high concentration of iron, which flows directly into Bens Creek, affecting the trout fishery. A system had to be designed and put into place to prevent further future damage to the aquatic life in Bens Creek. In 1992, a grant was applied for to passively treat the Rock Tunnel discharge with oxidation, precipitation of iron and manganese, reconfiguring stream flow, and planting vegetation. The enhancement removes an estimated 20 tons of iron, 4.5 tons of aluminum and 0.5 tons of manganese per year that once flowed into the popular trout stream, which in turn flows into the Stonycreek River.

The treatment site was limited physically by the steep slope and roadway above the site, flood plain below the site and what the EPA Region 3 wetland specialist designated as a protected wetland on the upstream side of the site. While 5 acres was donated, only approximately 2 acres were actually usable after the finish of rough grading. The final design consisted of serpentine, rock lined channels and two settlement ponds before discharge into the stream. Although the project was successful in removing a great deal of iron, it was far from perfect in part because it had been squeezed onto the limited space available. A contingent of volunteers from MLTU, Somerset Conservation District, SCRIP, Southern Alleghenies Conservancy, Somerset County Conservancy, Paul C. Rizzo and Associates and the National Guard worked to eliminate the short circuiting of the Rock Tunnel AMD treatment system in November of 2003. With the increased water flows of 2003, the system required some alterations in order for the water entering the system to maintain its retention time to drop out the iron laden sediment before entering the Bens Creek.

Thanks to the volunteer efforts, the goal was achieved. The system is now functioning to its original capacity and the water quality of the Bens Creek is again being protected from the ravages of AMD.

In Jan, 2006, an abandoned mine reclamation project proposal had been submitted for a discharge flow measuring device to be put in place (a weir). This will help to increase the important data needed to update the actual amount of the pollutional discharge being handled by the passive treatment system. This data will be used in the future to apply for much needed grants to use to put in place an operation and maintenance plan with increased updated enhancements to the treatment system to increase its efficiency. No treatment system is without flaws.