Hydraulic fluids containing polychlorinated biphenyls (PCBs) had impacted the site’s soils and groundwater resulting in the need for active remediation. RACER Trust, created in 2011 following the bankruptcy of GM and tasked with clean-up of this 89ha site, hired us to provide remedial design, construction oversight and certifying engineer services, which had to meet objectives specified in the EPA Record of Decision.
We prepared several remedial designs and action plans to guide the excavation and management of thousands of cubic metres of PCB-impacted soils, construction and implementation of a groundwater extraction and treatment system, and construction of a 7ha landfill cap that complies with the Resource Conservation and Recovery Act. Our landfill/geotechnical engineers and geologists/hydrogeologists prepared the remedial design for the cap, which included:
- Evaluating cap components using the hydrological evaluation of landfill performance (HELP) model to estimate and manage stormwater runoff, infiltration and flow rate
- Assessing potential gas generation and frost penetration impacts
- Completing a geotechnical analysis to confirm cap stability
- Evaluating interface slippage between cap layers
- Quality control testing protocols for all natural and
synthetic cap materials
The cap involved removing and replacing 91,750m3 of buried material, resulting in the creation of a 45m wide buffer zone between the toe of the landfill site and the adjacent property. Our design also included temporary precautionary elements, such as a 6m high, 220m long dust-control fence and a series of contact stormwater basins and berms to prevent migration of impacted dust and stormwater.
The landfill cap comprised several layers of natural and synthetic materials, including compacted soil, sand, topsoil, geomembrane, geotextile, geosynthetic clay liner and geocomposite. We negotiated removal of a gas management layer, resulting in a significant cost saving for our client. Following its completion, our NY licensed professional engineer certified the landfill cap, confirming its construction in line with the approved remedial design. When all remedial actions are completed, RACER Trust intends to transfer the property for redevelopment.