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Releases of creosote and pentachlorophenol (PCP) at a New Brighton, Minnesota wood treatment facility, resulted in widespread soil and groundwater contamination. Site investigations lead to the facility’s inclusion on the National Priorities List (NPL), and the Minnesota Pollution Control Agency was designated lead regulatory agency. Biological treatment was the preferred remedy for 18,000 yd of contaminated soil, and Biogenie was contracted to design, construct and operate an Biopile to achieve the remedial objectives.

Most project owners and remedial managers perceive the Biopile proc ess as a passive remediation technology, not fully appreciating the scientific and engineering expertise required to design and operate an effective Biopile. This paper highlights the “behind the scenes” efforts of the scientific and engineering team responsible for a Biopile project, and specifically how those efforts achieved difficult remedial objectives within a treatment performance guarantee contract.

The New Brighton project required that an Biopile be used to achieve site reuse criteria of 10 mg/kg PCP and 5 mg/kg cPAHs, with a schedule dictating operation during winter months reaching −22°C. Biopile operating parameters were developed during laboratory Treatability Studies designed to optimize the biodegradation capacity of indigenous microorganisms. The TS included the configuration of miniature Biopiles with various amendment and operational strategies to stimulate and sustain preferential bacteria. Additionally, specific operational parameters were developed to biodegrade soil containing a large percentage of highly impacted woodchips.

An engineering team applied the TS results during scale-up Biopile design and the project team mobilized to the site for construction. Average PCP reduction rates achieved 95% for soils (Phase I) and 76% for soils containing wood chips (Phase II), and over 96% of the contaminated soil achieved treatment criteria for reuse at the site.

This past decade has seen financial and volunteer investment in a cleaner, more accessible Neponset River. With these tangible improvements has also come a campaign to re-orient the public, and their perception of the river, from its previous reputation as an “open sewer” to a new role as a habitat for anadromous fish, venue for recreation on its waters, celebrations on its banks, and an inspiration for revitalizing the village of Lower Mills. From an ecological perspective, the Neponset is unique among urban rivers as its estuary remains largely intact and only two dams prevent anadromous fish from reaching fifteen miles of free-flowing habitat. However, the U.S. Geological Survey has documented elevated levels of polychlori nated biphenyls (PCBs) in the soft sediment impounded behind the two dams and the water column in the lower five miles of the Neponset River.

Decision-making about river restoration and sediment remediation must proceed concurrently when traditionally they would proceed on separate regulatory pathways. In addition, alternatives for fish passage and ecological restoration must not constrain remediation options and, conversely, remediation options must not limit the feasibility of alternatives for fish passage and ecological restoration. This workshop explores a range of potential remedial options, from traditional to innovative in the context of an ecological restoration effort that includes dam removal among the suite of alternatives.

The U.S. Geological Survey studied sediment and water quality, with an emphasis on polychlorinated biphenyls (PCBs), in the bottom sediment and water of the Neponset River. The USGS completed this study in cooperation with the Riverways Program of the Massachusetts Executive Office of Environmental Affairs Department of Fish and Game, and the U.S. Environmental Protection Agency. The major findings of this study were: human activities have adversely affected sediment quality in the Neponset River; with the exception of polyaromatic hydrocarbons and PCBs, contaminant concentrations are similar to those of other urban rivers; sediment contaminant levels may adversely affect aquatic life and human health; PCBs continue to be released into the Neponset River; and PCBs in the water may have toxic effects.

The Neponset River drains a landscape that has been disturbed by human beings for hundreds, possibly thousands, of years. The watershed is now intensely developed and modified to accommodate built environments. Deliberations regarding restoration and cleanup of the Neponset (and other rivers in urban landscapes) will benefit from a set of principles to guide activities and a decision context to provide a framework for competing considerations. This paper proposes a draft suite of eight principles that, together, offer social, scientific, and engineering foundations for decision making. Those principles are consolid ated in a decision model incorporating trade offs among the value of the habitat in place, the potential value of restoration activities, habitat destruction inherent in remediation technologies, risks associated with exposure to indust rial chemicals now in the ecosystem, and the potential risk-reduction benefits of chemical remediation. We conclude that optimal management decisions must account for and balance the considerations inherent in each of these decision categories.

Environmental restoration of the Neponset River will represent numerous complexities due to chemical impacts and the existing urban and suburban infrastructure coupled with natural geomorphic processes. The purpose of this paper is to provide a perspective on these complexities to aid in development of a sound strategy for remediation and restoration activities.

Remedial approaches and options for the Neponset River in Southeaster Massachusetts are described. The advantages of combining restoration, in particular restoration of the river as an ecological resource, with remediation is identified. Dredging and capping are identified as possible remedial approaches. Dredging in the small areas be hind the dams where PCBs are concentrated was identified as potentially very effective. Capping over larger areas requiring remediation was also identified as effective and also as contributing directly to improvement in habitat values for the river.

capping manages contaminated sediment on-site without creating the removal, transportation, and disposal exposure pathways associated with dredging. PCB mass, a perceived surrogate for risk posed by PCB-contaminated sediment, remains on site during capping projects creating concerns over the 1) duration of chemical i solation provided by sediment caps in advection dominated sediment systems and 2) the potential for PCB mass reduction by biotic and abiotic means during periods of chemical isolation. This study characterizes and compares commercially available sorbents to amend traditional sand caps by measuring properties relevant to advective-dispersive transport through porous media and uses these properties as inputs to a numerical model that predicts the performance of thin sorbent layers as sediment cap media in advection and diffusion dominated systems. Thin layer (1.25cm) sorbent amendments include thermally altered carbonaceous materials (coke and activated carbon) and soil. Sorbents provide chemical isolation of PCB-contaminated sediment in the same order (activated carbon — coke and soil-sand) as measured (highest to lowest) sorption Freundlich constants and sorption capacity. All sorbents outperform sand, coke and soil behave similarly. Thin (1.25cm) activated carbon layers chemically isolate PCB-contaminated sediment in advection-dominated systems for hundreds to thousands of years allowing time for natural attenuation.

River cleanup and restoration efforts pose significant legal and technical challenges for state and other regulatory agencies. Efforts are often conducted under different authorities, particularly CERCLA (Superfund) and NRDA rules. Wisconsin is home to a number of cleanup and restoration sites. The experience of project managers who worked for the Wis consin Department of Natural Resources on the Fox River and other cleanup and restoration site projects is presented. A number of common issues affect restoration projects. At many sites, human use has significantly affected the landscape and the presence of dams will have altered the function and habitat of river systems. Dam removal is a tool of choice for restoration but the appropriateness of removal can be influenced by: the presence of contaminated sediments, public acceptance, public safety and floodplain management. Consequently, restoration is typically more difficult than just dam removal. The presence of contaminated sediments is a big hurdle to project implementation. To move forward with cleanup and restoration where contaminated sediments exist, it may be necessary to work under CERCLA, NRDA, and other processes. Regardless of the processes used, project managers should use a diverse range of methods that collectively document the need and best approach for action at the site. Most importantly, regulatory agencies should combine CERCLA and NRDA processes for synergy and leverage but be aware of pitfalls where these processes can conflict. The combined results of CERCLA and NRDA efforts can create leverage for settlement by demonstrating that slower, less complete cleanup actions can escalate damages and associated costs. This can in turn provide an economic incentive for more extensive cleanup in order to reduce overall liabilities in the form of resources damages and promote development of remedial actions that facilitate overall restoration efforts.

Hamilton Harbour is located on the western end of Lake Ontario and has an area of approximately 31 square kilometers. The harbour has been designated by the International Joint Commission (IJC) as one of the 42 Areas of Concern (AOCs) within the Great Lakes. Most fine-grained sediments in the harbour exceed sediment quality guidelines at the severe effect level due to contamination by both metals and organic compounds such as PAHs and PCBs. Current investigations are concentrated on two areas of the harbour called Randle Reef and Windermere Arm. The Randle Reef “hot spot” contains the most highly contaminated sediment for PAH concentrations in the harbour. Extensive information on sediment physical and chemical properties was collected by coring and offs hore boreholes. Bioassays were carried out to determine sediment toxicity. A range of remediation alternatives has been considered, including removal and treatment. The current preferred alternative is an enginee red containment facility (ECF), which will contain contaminated sediments within the footprint of the structure. In addition, dredged sediment from other contaminated sites in the harbour will be placed in the ECF. Windermere Arm is a 50-ha narrow channel situated in the southeast portion of the harbour. Contamination in Windermere Arm is not as severe as that found in Randle Reef. Recent sediment surveys in the area, however, yielded higher PCB values in surficial sediments than previously reported. Sediments in Windermere Arm are also subject to considerable physical disturbance due to extensive ship traffic. For this reason, historical sediment contamination occurring in deeper sediments also has to be considered as a potential risk to the aquatic environment.

This paper describes the first phase of a multi-phase project currently underway to delineate a chlorinated solvent (primarily trich loroethene [TCE]) plume in groundwater downgradient of a former industrial site. The TCE was introduced to the subsurface environment at the site, resulting in a groundwater plume extending from the on-site source to a wetland-stream complex, the primary discharge point for groundwater migrating from the site. To date, the plume has been delineated from the source to the upgradient edge of the wetland via quarterly groundwater sampling through a network of monitoring wells. At the upgradient edge of the wetland, TCE concentrations in groundwater remain elevated, while products of reductive dechlorination are present. Additionally, surface-water sampling indicates that the solvent plume is discharging to a small stream that drains the wetland.

The first phase of the plume delineation project consisted of a recently completed solvent plume discharge evaluation (SPDE), with the objective of evaluating the locations of solvent plume discharge to the wetland stream. The SPDE was cost-effectively conducted by deploying passive diffusion samplers (PDSs) in the wetland stream sediments at 45 locations along a 1,900-foot length of the stream. Once equilibrium between the PDSs and the sediment pore water was attained, the concentrations of chlorinated ethenes in the PDS samplers were measured. The analytical results were mapped as a function of stream length and indicate a definitive point of plume discharge to the stream and a possible plume fringe. The results were also correlated with sediment type, water-quality parameters, and piezometric measurements obtained during this work. The ratios of degradation products to TCE were greater in the PDS samplers than ratios observed at upgradient monitoring locations, indicating an increasing natural attenuati on potential as the plume migrates through the wetland. The results of the SPDE were used to focus the next phase of plume delineation, currently being conducted. Preliminary results of the plume evaluation compare well to the SPDE results.