Coakley Landfill Deep Bedrock Investigation Study Results
EPA Superfund Site Coakley Landfill in Greenland and North Hampton, NH
Deep Bedrock Investigation Draft report presented in December 2021
Haley Ward and Sanborn Head Associates developed and presented a nearly 950 page draft report of the Deep Bedrock Investigation to the Environmental Protection Agency, the Coakley Landfill Group (CLG) and the Seacoast Cancer Cluster Investigation Commission in January of 2022.
The Bedrock report has been processed and is available at http://www4.des.state.nh.us/IISProxy/IISProxy.dll?ContentId=4969036
The report covered sampling activities from April 2017 through October 2021 and the following four conclusions were published in the executive summary.
Conclusion 1
PFAS and 1,4-dioxane are migrating westward from the landfill through bedrock and overburden sediments consistent with principal groundwater flow direction based on observed hydraulic gradients. Groundwater is subsequently discharging to, and surface water is collecting in, a wetland complex located west of the landfill. Surface water flow from this wetland complex is both south towards North Road and north towards Breakfast Hill Road, consistent with dominant fracture strike (and a bedrock valley or trough). To a lesser extent, PFAS and 1,4-dioxane are also migrating east away from a bedrock topographic high located east of the Site boundary.
Conclusion 2
Along established flow paths, the contaminant migration rate is limited and the interconnectedness of fractures in deep bedrock is also limited.
Conclusion 3
Pumping of active private drinking water wells for water supply is not influencing contaminant migration or groundwater gradients within the contaminant plume.
Conclusion 4
Elevated concentrations of PFAS in Berry’s Brook and the wetland complex, as compared to overburden groundwater concentrations, are the result of discharge JN: 10424.016 xi Deep Bedrock Investigation Final Report Coakley Landfill Superfund Site of the shallow groundwater to the surface water and include a significant contribution from landfill surface water runoff.
The report reported that three predominant migration pathways exist in deep bedrock.
• Roughly north-south along the bedrock trough, which is the primary pathway
• Secondary/limited migration along the predominant northeast-southwest strike in bedrock
• Secondary/limited migration East-Southeast – West-Northwest along cross-cutting fractures parallel to the secondary set of lineaments.
The report stated that routine sampling of private water supply wells completed in deep bedrock indicated that little to no significant migration in the deep bedrock has occurred.
The report updated the Conceptual Site Model (CSM) based on detailed review and analysis of data collected during deep bedrock investigation activities conducted between April 2017 and October 2021.
The EPA will analyze the data collected and provide further recommendations to the Coakley Landfill Group and the Seacoast Cancer Cluster Investigation Commission by June of 2022 about any and all further remediation procedures.