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RISK-BASED PROCEDURES USED TO SUPPORT REMEDIATION OF A GROUND WATER- SURFACE WATER TRANSITION ZONE CONTAMINATED WITH CHLOROBENZENES
Citation:
Impact/Purpose:
Field screening techniques and ecological risk assessment were used to estimate risks and set clean up goals for contaminated media at the Eastland Woolen Mill Superfund Site in Corinna, Maine.
Description:
Risk-Based Procedures Used to Support Remediation of a Ground Water - Surface Water Transition Zone Contaminated with Chlorobenzenes (Eastland Woolen Mill Superfund Site, Corinna, ME) In-situ and laboratory toxicity, sediment-toxicity identification evaluation (SIE), benthic macroinvertebrate and hyporhetic (ground - surface water transition) zone community structure/function studies were performed in a small river downgradient of a former textile manufacturing facility in central Maine. Surface water, sediment, and groundwater were contaminated with organic solvents (particularly chlorobenzenes) as the primary chemical stressors of interest plus several pesticides and metals. Ecological studies, field and lab tests were designed to support an ecological risk assessment and various interim management decisions that focused on two primary contaminant migration pathways (groundwater discharge to surface water and sediment particle transport/deposition). Test chambers for in-situ toxicity or bioaccumulation contained water fleas, amphipods, midge larvae, or oligochaete worms, and were placed in the water column and the sediment/water interface. Survival and bioaccumulation was evaluated in both acute or chronic exposures (48 to 96-h). In-situ SIE and solid-phase SIE in the lab identified organic contaminants (not metals) as the class of chemicals associated with observed toxic effects. However, nutrients and low dissolved oxygen were potential confounding variables. A separate study of benthic macroinvertebrate re-colonization potential and microbial species diversity in affected hyporheic zones, relative to reference, had focused on ecological integrity as expressed through community structure and function. Overall study results indicated effects were significant in both in-situ and lab toxicity tests, SIE, and upon stream ecology in hyporheic zones on site. Spatial variability was observed in biological responses in-situ and correlated very well with microscale patterns of ground water discharge/ recharge (i.e., up or downwelling). Results of lab and in-situ toxicity were in agreement based on effects on water flea survival and reproduction. Toxicity was observed in association with exposures to hyporhetic zones, shallow ground water, or whole sediment, and not surface water at the same locations. Preliminary remediation goals for sediment were proposed for chlorobenzenes or dieldrin based on data analysis of these and other toxicological results.
