McPherson Branch Demonstration Site

In 1998, Glenn Springs Holding, Inc. (GSHI) constructed a demonstration passive wetland that captured water from McPherson Branch, a small (165 hectare/410 acre) first-order watershed with a mono culture of pine growing on the eroded soils.

Near its confluence with North Potato Creek, this stream exhibited low pH, moderate acidity, and elevated metals. Additionally, stream remediation was challenged by the high sediment load from the eroded areas upstream. Even paved roadways located well above the creek channel were regularly inundated and covered with sandy silt from the barren areas. The relatively low concentrations of metals and acidity indicated the drainage was a good candidate for passive treatment. Evidence of very high flows and obviously high sediment loads required an innovative approach to implementing passive treatment. This project was detailed in a 2002 American Society of Mining and Reclamation presentation by Ben B. Faulkner.

Also in 1998, GSHI removed a 7,600 cubic meter (10,000 cubic yard) pile of mine waste proximate to McPherson Branch, and documented a rapid acceleration of the improvement in water quality in the branch that had been slowly occurring since the mines became idle decades ago. Since October, 1998, the two-acre anaerobic passive treatment system has successfully routed base flow from McPherson Branch through the cattail-dominated wetland, and by limestone dissolution and bacterial sulfate reduction has converted the acidic, metal-laden stream to an alkaline discharge with greatly reduced concentrations of problem metals. GSHI has recently completed an adjoining one-acre, three-cell aerobic wetland that increases dissolved oxygen in the flow and provides retention time for sulfide volatilization and oxygen demanding processes to occur. While increasing alkalinity and hardness, the rock filter system also provides habitat for manganese reducing bacteria.

An additional benefit of the geosynthetic clay lined system is to limit the recharge of seepage under the McPherson roadway from the old roaster yard where the wetland system was constructed. Additional regrading and revegetation of the area surrounding the wetland system was constructed. Additional regrading and revegetation of the area surrounding the wetland has also recently been accomplished.

A bio survey in 2002 indicated that the most important limiting factor for aquatic life in McPherson Branch downstream of the wetland was not any chemical problem with the stream, but lack of habitat. Years of sediment deposition and poor vegetation survival in and along the stream provided poor habitat for aquatic insects. A 65 meters (215 feet) "restored stream segment" was constructed in 2003 to improve habitat and to demonstrate that McPherson Branch, having passed through the treatment wetland, will support aquatic life. Shrubs and plants native to the area were placed alongside recovering species. Rock, cobbles and aquatic insects were "transplanted" to the stream from nearby Belltown Creek and tributaries of North Potato Creek.

Annual bio monitoring in this restored stream segment will evaluate changes in habitat, macro invertebrate populations, and water chemistry. GSHI biologists are carefully monitoring the performance of the wetland and the aquatic life in the restored stream segment to refine plans for stream recovery efforts elsewhere in the basin. In addition, bench scale tests of passive systems are being conducted to determine the optimum components and sizing for future passive applications at other sites in the Basin.

-top-