Rennie Farm – 1,4-Dioxane Investigation and Remediation

Challenge

Following remediation and closure of a former medical research waste disposal facility for radiological waste, 1,4-dioxane was detected in groundwater. Historical waste included scintillation fluids used in radiological research that contained 1,4-dioxane. The project required evaluating contaminant transport through overburden and fractured bedrock groundwater systems, including potential migration to downgradient private water supply wells. Designing and constructing a groundwater remedial system also required addressing a remote location, wetlands, wooded and steep terrain, an active roadway, and limited electrical service.

Solution

GZA’s investigation included multiple phases of groundwater monitoring well installation and testing, bedrock mapping, and surficial and borehole geophysical evaluations to identify fracture patterns and potential preferential pathways for groundwater flow and 1,4-dioxane transport. Sampling included more than 140 private water supply wells, surface water, and community and public water supplies. Radionuclide sampling and analysis addressed the site’s historical waste disposal, and laboratory waste excavation included evaluation of both 1,4-dioxane and radionuclides. Delineation of the source and extent of dissolved-phase transport supported remedial system design and issuance of a groundwater management permit.

GZA designed and constructed a groundwater extraction system using 29 wells in overburden and fractured bedrock. Pneumatic pumps receive compressed air from compressors at three pumping locations, each requiring building construction or renovation, including abatement and demolition. Construction included access roadways and buried and aboveground air, water, and control lines. Directional drilling provided a utility conduit beneath an active roadway, while aboveground conduits, including a heated utilidor, limited wetland impacts.

GZA specified the groundwater treatment system components and installed the system in a treatment building constructed within a 53-foot-long shipping container placed on an engineered pad. Treatment uses resin filtration with on-site steam regeneration; condensate is treated using granular activated carbon. A supplemental generator meets the electrical demand for steam regeneration beyond the available single-phase service, and generators at each pumping location provide emergency power.

Benefit

GZA’s integrated investigation, design, and construction services translated characterization of a complex groundwater system into an installed extraction and treatment system addressing 1,4-dioxane in both overburden and fractured bedrock. The investigation established the source and extent of dissolved-phase transport, evaluated potential migration to water supplies, and supported issuance of a groundwater management permit. Site-specific construction approaches accommodated challenging terrain and an active roadway while limiting wetland impacts. On-site resin regeneration, supplemental electrical capacity, and emergency power provisions equipped the system to meet its treatment and operating requirements at a remote site.