Development and Implementation of Integrative Bioassessment Techniques to Delineate Small Order Acid Mine Drainage Impacted Streams of the North Fork Powell River, Southwestern Virginia

Abstract

Acid mine drainage (AMD) results from the oxidation of pyretic mineralogy, exposed by mining operations to oxygen and water. This reaction produces sulfuric acid and liberates heavy metals from the surrounding mineralogy and impairs water quality and freshwater communities. The U.S. Army Corps of Engineers has begun an ecosystem restoration project to remediate the abandoned mine land (AML) impacts to the North Fork Powell River (NFP) and is utilizing the ecotoxicological rating (ETR) system to delineate these affects to focus restoration efforts. The ETR was developed to summarize the integrative data into a single number ranging from 0 to 100, which is descriptive of the environmental integrity of a sampling station. The ETR is conceptualized to work as an academic grading scale (0 through 100), rating reference stations with A's (90-100) and B's (80-89) and impacted stations with C's (70-80), D's (60-70) and failures (F = 60). Two rounds of ETR investigations have evaluated seven headwater tributaries to the NFP including investigations of Ely and Puckett's Creek from 1997 and 1998. This thesis contains the results of the second series of ETR investigations at 41 stations in Cox Creek, Jone's Creek, Reed's Creek, Summers Fork, Straight Creek, and areas in the NFP. Eight stations were recommended for reclamation; CC 03, JCRF2 02, JCRF2 01, RCPS 09B, RCPS 11B, SULF 01, SU 02, and SU 01. Summers Fork was the most severely impacted watershed of the second round of ETR investigations. An effort to streamline the ETR to the most ecologically predictive parameters was successful in creating a system more time and cost efficient then the initial ETRs and exclusive of benthic macroinvertebrate surveys. The Modified ETR streamlined the ETR to just 5 parameters including; mean conductivity, mean Asian clam survival, mean aluminum (Al) and manganese (Mn) in the water column, and mean habitat score to describe the AMD impacts to small headwater streams. Also, an investigation was conducted to determine the mode of toxicity, (i.e., exposures to metal contaminated surface waters or sediments) by which Al and iron (Fe) dominated AMD impairs benthic macroinvertebrate communities. It was found that water column exposures both within and beyond the zone of pH depression are the most likely mode by which AMD impairs the benthic macroinvertebrate communities of the NFP.