Remedial Investigation/Feasibility Study, Hingham Former Burning Grounds


Location: Hingham, Massachusetts

USACE, New England District

Overview:

  • Geological, Geotechnical, Geothermal, and Geophysical Investigations
  • Groundwater Investigation and Modeling
  • Soil and Sediment Investigation
  • Environmental Chemistry, Data Collection, Management and Interpretation
  • Human Health Risk Assessment
  • Baseline Ecological Risk Assessment (BERA)
  • Sediment Toxicity Testing
Sampling Seep Hingham Avatar Environmental

Description:

Hingham Former Burning Grounds (FBG) is a former open burning/open detonation (OB/OD) munitions disposal area at the former Hingham Naval Ammunition Depot Annex, currently within the Wompatuck State Park. Avatar is currently completing the Remedial Investigation and Feasibility Study (RI/FS) for the US Army corps of Engineers under its Formerly Used Defense Site (FUDS) program. Technical tasks have been conducted as multiphase investigations based on an initial data gaps analysis. All work performed by Avatar at this FUDS has been conducted in accordance with CERCLA.

Avatar completed geophysical and intrusive investigations to identify geo-anomalies to determine the presence of ordnance and explosives (OE) and munitions and explosives of concern (MEC) in the FBG. This project to date has included multiple rounds of sampling. Media have included overburden and bedrock groundwater, surface and subsurface soils, hydric soils, and surface water and sediments. To supplement an existing network of monitoring wells installed by previous contractors, Avatar installed bedrock and overburden wells. In addition to slug tests performed on existing and new wells to inform related hydrogeological fate and transport groundwater models, Avatar has conducted four rounds of groundwater sampling to date. To augment soil monitoring results collected previously, Avatar collected additional surface and subsurface soil samples throughout the investigation area and from background locations. Soil sampling included the use of state-of-the-art Incremental Sampling Methodology (ISM) at four areas of suspected explosives contamination. In addition, soil sampling was also conducted at several slag piles using ISM.

Located adjacent a large wetland complex containing regulatory-sensitive vernal pools and 350 ft upslope of the Aaron River, the FBG has been shown to be a source of runoff and groundwater discharge of contaminants to the wetlands and the river. Prior to the investigations conducted by Avatar, no data were available to determine the extent to which the OB/OD operations may have contributed to contamination of the surrounding wetlands. As part of the ecological investigation, Avatar surveyed the adjacent wetlands, identified potential vernal pools, and mapped groundwater seeps that serve as a source of water to wildlife. Surface water and sediment samples were collected from these habitats. Based on the results and the presence of amphibians in the pools, 10 day sediment bioassays were conducted with amphibians (wood frog or spotted salamander) of the vernal pools. In addition, 28 day amphipod tests were performed to assess the potential risk to fairy shrimp. Amphipod assays were conducted for the sediments of the Aaron River where elevated levels of lead and possibly other chemicals may represent an ecological risk. An extensive background monitoring program of wetland hydric soils and sediments from vernal pools was conducted. These data are being compared with site data and evaluated as part of the Uncertainty Analysis of the Human Health and Ecological Risk Assessments. Should remediation be required, these background data will serve to inform remedial action requirements.

All analytical data underwent Tier 2 and Tier 3 (explosives) chemistry validation to meet data requirements for use in the risk assessments. All environmental chemistry data were incorporated into a project database that allowed for a streamlined approach for management and interpretation.

Avatar has prepared a human health risk assessment (HHRA) and a screening level ecological risk assessment (SLERA) for the FBG to inform risk management decisions in the FS in accordance with requirements under CERCLA. The HHRA evaluates the risk associated with potential multi-media exposure to contaminants by current recreational visitors, park workers, and trespassers, as well as potential future residents. The SLERA evaluates the potential risk to fish and wildlife from exposure to contamination in terrestrial, wetland, and aquatic habitats. In addition, the SLERA incorporates the use of the site-specific sediment bioassays for amphibians and invertebrates. The Human Health and Ecological Risk Assessments incorporate innovative spatial-weighting of the contaminant distributions to better estimate potential exposure instead of deferring to the more typical conservative approach used in most risk assessments.

“Contractor is responsive and cooperative. Project is progressing as planned per the schedule. Contractor is technically proficient and has a team approach. Contractor has excellent rapport with Corps project team. Project management skills are excellent” – Carol Charette, USACE Project Manager
Sampling Seep Hingham Avatar Environmental