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Final Report; Arsenic Fate, Transport and Stability Study; Groundwater, Surface Water, Soil And Sediment Investigation, Fort Devens Superfund Site, Devens, Massachusetts
FORD, R. G., K. G. SCHECKEL, S. ACREE, R. ROSS, B. LIEN, T. LUXTON, AND P. CLARK. Final Report; Arsenic Fate, Transport and Stability Study; Groundwater, Surface Water, Soil And Sediment Investigation, Fort Devens Superfund Site, Devens, Massachusetts. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-09/063, 2008.
To provide a technical evaluation of the distribution and flux of arsenic in shallow groundwater discharging into Plow Shop Pond, and the fate, transport and stability of arsenic in sediments and surface water within the portion of Plow Shop Pond that is the primary receptor for plume discharge (i.e., Red Cove).
This document presents results from the Fiscal Years 2006-2008 field investigation at the Fort Devens Superfund Site, Operable Unit 1 (Shepley's Hill Landfill) to fulfill the research objectives outlined in the proposal entitled, 'Fate and Transport of Arsenic in an Urban, Military Watershed' and the 'Arsenic Fate, Transport and Stability Study' QAPP and Work Plan. The purpose of this study was to provide the USEPA Region 1 with a technical evaluation of the distribution and flux of arsenic in shallow groundwater discharging into Plow Shop Pond, and the fate, transport and stability of arsenic in sediments and surface water within the portion of Plow Shop Pond that is the primary receptor for plume discharge (i.e., Red Cove). Analysis of hydrologic and chemistry data collected from the Red Cove Study Area during September 2005 to November 2007 indicated that groundwater with elevated concentrations of arsenic currently discharges into Red Cove. Based on current and historical data for the distribution of arsenic is shallow sediments within Plow Shop Pond, the arsenic concentrations observed in Red Cove sediments appear consistent with groundwater discharge as a primary source of arsenic contamination. The distribution of arsenic flux measured at RSK well clusters in combination with the piezometric surface depicting groundwater flow potential for the aquifer underlying the landfill indicate that the primary source of arsenic originates from a direction west-southwest of Red Cove. Presently, concentrations of arsenic observed in surface water within Red Cove are, in part, controlled by the continual precipitation of iron oxides that sequester dissolved arsenic introduced from groundwater discharge or released by diffusion from contaminated sediments. Since the cove is a biologically productive system due to the continual, seasonal supply of degradable organic matter from aquatic plants, reducing conditions are anticipated to prevail at the sediment-surface water interface. Thus, while the continual oxidation and precipitation of ferrous iron within the water column will serve to remove a portion of dissolved arsenic from the water column, the precipitated iron oxides are susceptible to re-dissolution and release of sequestered arsenic. The result of this internal recycling of arsenic between sediments and overlying surface water is the potential maintenance of dissolved arsenic concentrations within the water column that may exceed ambient water quality criteria. Thus, the contaminated sediments could pose a long-term exposed risk to aquatic life within Red Cove. If an unacceptable risk is identified in Red Cove due to contaminated groundwater discharge and/or in-place contaminated sediments, it is recommended that evaluation of potential remedies include consideration of mitigating both plume discharge and release of contaminants from sediments.
URLs/Downloads:FINAL REPORT; ARSENIC FATE, TRANSPORT AND STABILITY STUDY; GROUNDWATER, SURFACE WATER, SOIL AND SEDIMENT INVESTIGATION, FORT DEVENS, ETC.
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