Definition of the Problem at Site 42
The PA Department of Environmental Protection (DEP) accepted a proposal by the Northumberland County Conservation District (NCCD), the Shamokin Creek Restoration Alliance (SCRA), and Bucknell University (BU) to treat abandoned mine drainage at Site 42. The Shamokin Creek watershed has been significantly degraded due to abandoned coal mine drainage. This effort addresses the most significant iron loading problem, Site 42 (site numbers refer to Coddry and Carpenter, 1972), in the Carbon Run subwatershed upstream of Scarlift Site 49. Site 42 contributes approximately 88% of the iron loading to the subwatershed above Site 49. We have installed a passive wetland treatment system to remove between 70-90% of the iron loading and add alkalinity to Carbon Run over 4 stream km (2.5 mi). The subwatershed has two main tributaries that have pH values in the 5-6 range, with relatively minor iron coating problems. The removal of iron in a limestone drain/wetland system at Site 42 should allow macroinvertebrates and vertebrates present in tributaries to begin to repopulate the main branch of Carbon Run. Recent studies have shown that iron oxidation rates are critical in determining whether wetland treatment will prove successful. Research at this system will use iron oxidation rates to develop wetland sizing criteria which should be applicable statewide.

The Carbon Run subwatershed is located in the southwest section of the Shamokin Creek Watershed and has a total area of 23 sq. km2 (9.0 sq. mi). Lower reaches of the subwatershed (approximately 0.5 sq. mi; downstream of the proposed treatment) are in the town of Shamokin. The upper subwatershed is mainly unpopulated forest land with some wetlands with mine-related surface and underground disturbances. There is currently one active mine in the subwatershed. Although approximately half of the subwatershed is covered with mine spoils (most are pre-1969), significant ecological succession has taken place on many of the piles, there has been reclamation of some areas, and only a small fraction of the land is nearly barren.

We have chosen to remediate Scarlift Site 42, which is by far has the highest iron loading in the portion of the Carbon Run subwatershed above Scarlift Site 49. This portion above Site 49 is hereinafter referred to as "the subwatershed"; all site numbers refer to Scarlift numbers. Site 49 approximately doubles the flow of Carbon Run, with a discharge of 16.7 million cubic meters/day (6.3 mgd). It averages 25 mg Fe/L, and has an average iron loading of 1150 kg/day (2530 lb/day). The volume of flow and iron loading made Site 49 unsuitable for a first restoration project.

Operation Scarlift identified 13 mine discharges to the Carbon Run subwatershed with significantly varying water qualities. Recent surveys by SCRA members located all of these 13 sites. Ownership information, directions to sites, site descriptions, road access, some single-date flow and chemistry data have been collected. In addition, the DEP Bureau of Abandoned Mine Reclamation collected nine months of chemistry and flow data on Site 42 and three other sites in Carbon Run.

Site 42 is located on land owned by the Northumberland County Commissioners. It is an overflow (North Mountain Tunnel) from a deep mine that emanated from a culvert recently installed at the outlet of a mine tunnel. This work lowered a deep mine pool to allow access to deeper coal seams; mining operations have recently ceased. Because a mine permit is still extant in a nearby mine hydrologically connected to this discharge, care will be taken not to raise the level of the deep mine pool. The high dissolved oxygen concentrations ( approx. 4 mg/L) calls for an experimental approach to treatment. The discharge flows through a constructed ditch for 800 m before entering Carbon Run.

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