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The U.S. Department of Energy Portsmouth Gaseous Diffusion Plant is in the early stages of decommissioning and decontamination. During operations, the site drew a large amount of electric power and had multiple large switchyards on site. These are a source of polychlorinated biphenyls (PCB) contamination to both on-site and off-site streams. Some soil remediation has been completed in the main switchyard. During 2011 and 2012, fifteen sites were sampled at the surface (<10cm) and subsurface (20-30cm) to characterize the extent of PCB contamination, to identify weathering and migration of PCB contamination and to explore potential polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) contamination due to transformer fires and explosions in the 1950s and 1960s. Stagnant sites tended to exhibit more migration of contamination to deeper sediments than sites with fast-moving waters, and the highest concentrations were found at the bottom of a settling pond. A signature set of five dioxin-like PCBs were consistently found across the site with higher concentrations in carbon rich surface sediments. PCB concentrations had a significant inverse correlation with clay content, suggesting that PCBs did not bind to clays at this site. Remediation has reduced PCB concentrations throughout the site compared to levels found in previous studies and long-term upkeep of sediment lagoons is necessary to retain PCB and dioxin-rich sediments. The flow regimen, organic carbon and clay content play a very important role in the fate of PCBs in the environment at the surface as well as downward migration. [ABSTRACT FROM AUTHOR]

Hewett Fork in Raccoon Creek, Ohio was a large source of acid mine drainage (AMD) to the main stem of Raccoon Creek, impacting the biological community for several kilometers. To reduce this impact, the AMD treatment was implemented in the Hewett Fork subwatershed to treat water from the largest mine drainage source in the watershed near the village of Carbondale. From prior to installation of wetland treatment in 2000 and installation of the lime doser in 2004, the pH of the mine discharge has been raised from about 4 to about 9, which greatly improved biological communities in Hewett Fork and Raccoon Creek. During the summer of 2010, the doser was off-line for approximately 2 weeks. While the chemistry of Hewett Fork showed little lasting change due to non-treatment, biological surveys show the effect of temporary non-treatment. In the year and a half since the doser was off-line, surveys have shown that the fish community was seriously impacted due to non-treatment and it has not yet recovered; the macroinvertebrate community, on the other hand, showed little impact due to non-treatment, and has shown no lasting effect of non-treatment. [ABSTRACT FROM AUTHOR]

Acid mine drainage is a serious environmental problem throughout mining regions of the US and around the world. In Appalachia, reuse of steel slag from steel production as a source of alkalinity for treatment of acid mine drainage has become a common practice. In these systems, dubbed steel slag leach beds, relatively clean surface water is percolated through a bed of steel slag to add large amounts of alkalinity to the water before mixing it with acidic, metalliferous mine water. These beds do not operate consistently and their failure mechanisms are poorly understood. Using the experience of Raccoon Creek watershed in southern Ohio, the alkalinity distribution of the discharge of six steel slag leach beds is compared. Two of these beds are still functional, one has been abandoned and three are operating poorly. The difference in alkalinity distribution between these beds suggests that a carbonate-dominated alkalinity system is an indicator of a poorly performing steel slag leach bed, while a more even distribution between hydroxide, carbonate and bicarbonate may point to more ideal operating conditions. In eight laboratory column experiments, this evidence was then expanded upon by testing different mixed media substrates (differing mixes of steel slag, wood chips and river gravel) to see which provided the most ideal alkalinity distributions. The columns that had steel slag mixed either with wood chips or wood chips and river gravel outperformed the column with slag only in terms of alkalinity distribution, perhaps due to microbial processes or increased hydraulic conductivity without significant added calcium or carbon that could drive calcium carbonate precipitation within the beds and causing them to fail. [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) negatively impacts not only stream chemistry, but also aquatic biology. The ultimate goal of AMD treatment is restoration of the biological community, but that goal is rarely explicit in treatment system design. Hewett Fork in Raccoon Creek Watershed, Ohio, has been impacted by historic coal mining and has been treated with a calcium oxide doser in the headwaters of the watershed since 2004. All of the acidic inputs are isolated to a 1.5 km stretch of stream in the headwaters of the Hewett Fork watershed. The macroinvertebrate and fish communities have begun to recover and it is possible to distinguish three zones downstream of the doser: an impaired zone, a transition zone and a recovered zone. Alkalinity from both the doser and natural sources and physical stream parameters play a role in stream restoration. In Hewett Fork, natural alkaline additions downstream are higher than those from the doser. Both, alkaline additions and stream velocity drive sediment and metal deposition. Metal deposition occurs in several patterns; aluminum tends to deposit in regions of low stream velocity, while iron tends to deposit once sufficient alkalinity is added to the system downstream of mining inputs. The majority of metal deposition occurs upstream of the recovered zone. Both the physical stream parameters and natural alkalinity sources influence biological recovery in treated AMD streams and should be considered in remediation plans. [Copyright &y& Elsevier]