Climate Adaptation Profile: General Motors (Central Foundry Division)

Massena, New York

Site Description

The General Motors (Central Foundry Division) site is situated on approximately 218 acres of industrial and undeveloped land in an otherwise rural area bordering the St. Lawrence River, the Raquette River and the Mohawk Territory of Akwesasne. Past use of the site for metal casting involved generation of wastes that were disposed of in two disposal areas, an industrial landfill and four lagoons. As a result, polychlorinated biphenyls (PCBs) contaminated the groundwater, onsite soil, sediment in the St. Lawrence and Raquette Rivers, and soil and sediment on Tribal lands adjacent to or in Turtle Cove and Turtle Creek (within the St. Lawrence River Watershed). In addition, volatile organic compounds contaminated the groundwater and phenols contaminated lagoon sludge in the disposal areas.

Remediation Activities

Initial remedial work focused on contaminated materials in the St. Lawrence River. Contaminated sediments were dredged, solidified and disposed of at an offsite permitted landfill. A multilayer cap was installed over contaminated sediment remaining in two acres along the river’s shoreline and extending approximately 250 feet into the river. Remediation of Turtle Cove involved soil excavation as well as sediment dredging, with offsite or onsite disposal of the materials.

Work in the upland area involved excavating and solidifying contaminated sludges and soils from the four lagoons and offsite disposal of the materials at permitted disposal facilities through a phased approach. Material from the ”East Disposal Area” was consolidated in the onsite industrial landfill, and the combined waste was covered with an 18.3-acre composite cap supported by a groundwater extraction system. A 150-foot landfill setback was established to create a waste-free buffer zone along the Tribal border and St. Lawrence River.

To eliminate the potential for surface water contact with PCBs below the cleanup criteria, a minimum 6-inch-thick topsoil layer and overlaying demarcation fabric were emplaced above 0.5 to 6 feet of clean fill across the entire site (excluding areas where PCB-contaminated soil was earlier excavated and replaced by clean fill). Current work focuses on maintaining the landfill and sediment cover systems, extracting contaminated groundwater from eight recovery wells for ex situ treatment, and addressing the Tribal property’s contaminated soils and sediments.

Vulnerability to Climate Change Impacts

The site is vulnerable to riverine and upland flooding caused by extreme precipitation events or rapid snowmelt. For example, intense rainfall coupled with intense wind action in early 2017 caused record-high water levels and flooding in the Lake Ontario – St. Lawrence River System. Operations at the upstream Robert Moses-Robert H. Saunders Power Dam, which provides power to the Province of Ontario and State of New York, significantly influence the potential for onsite flooding.

Other vulnerabilities concern potentially more intense wave action and more frequent ice jams within the St. Lawrence River, which could result in scour of the shoreline/subaqueous sediment cap. The low temperatures in Massena during December, January and February currently average 13°F, 5°F and 7°F, respectively. Additionally, freeze conditions could affect other remedial components such as groundwater extraction pumps and stormwater drainage pipes.

Building Adaptive Capacity for Future Climate Scenarios

Designs of the onsite caps and plans for site restoration considered the hazards posed by projected climate scenarios in the region. The toe of the capped industrial landfill, which is situated near Tribal land, is approximately 15 feet above the historic average height of St. Lawrence River water nearest the site. This helps ensure long-term protectiveness of the site remedy under potentially higher river levels in the future.

The landfill capping system was designed to shed more than three times the surface water capacity required by New York regulations. The cap contains two rather than one drainage layer(s), each consisting of an 18-inch-thick layer of permeable soil and a layer of geonet. To further assure efficient drainage of rainfall or snowmelt that may enter the cap, the design included a network of 4-inch-diameter perforated pipes. Water captured via this drainage system is directed to a swale that surrounds the cap and conveys the water to an outfall at Turtle Cove.

The landfill cap design also called for the Turtle Cove outfall structure to consist of a 24-inch-diameter pipe (rather than typical 16-inch-diameter pipe) to manage the estimated peak discharge of a 25-year, 24-hour storm event. Due to the installed pipe’s unexpected vulnerability to ice during winter months, which resulted in outfall damming and hindered stormwater discharge to Turtle Cove, the pipe was later replaced with a 2- by 4-foot concrete box culvert. This modification reduced the likelihood of ice-related damming while tripling the peak discharge capacity of the outfall, which can now accommodate a 100-year storm.

The subaqueous portion of the sediment cap consists of a minimum 6-inch sand filter layer and a minimum 6-inch gravel bedding layer that are protected by a minimum 6-inch layer of stone armor. Inspections by U.S. Environmental Protection Agency (EPA) divers in 2017, 2019, and 2023 revealed no evidence of ice scour or washouts negatively affecting the sediment cap.

Eighty-four acres of the uplands covered with clean fill were graded in a manner that promotes precipitation dispersal via sheet flow, thereby reducing potential soil erosion and associated gully formation. Management of onsite stormwater was enhanced by rehabilitating an existing stormwater pond and constructing an engineered wetland. The pond and wetland were designed to temporarily retain excess stormwater shed from the southern section of the capped landfill and runoff from other areas. To protect the groundwater extraction system from saturated soil as well as freeze conditions, the system’s mechanical and electrical controls were installed in waterproof vaults positioned at depths below the site’s frost line.

Following remediation of Raquette River sediments and bank soils, riprap was installed below the river channel’s high water mark to minimize erosion. Native shrubs known to thrive in riparian buffers (red osier dogwoods) were planted on Raquette River banks to further prevent erosion while also filtering out pollutants carried in stormwater runoff. Approximately 68 acres (31 percent) of the upland areas were revegetated via seeding. Areas used for stormwater management received a seed mix intended for saturated conditions.

A layer of gravel was installed across the 20-acre footprint of the former plant building to aid infiltration and support the site’s anticipated reuse for industrial purposes. The site’s fourth (2020) five-year review indicated the remedy had not experienced damage such as soil washouts or broken drainage pipes due to storm events over the previous five years.

Superfund Climate Resilience

EPA provides additional information about approaches for building climate resilience at Superfund sites.

Point of Contact

• Vicki Rubino, U.S. EPA Region 2

References

• GM Cleanup a Reality, Central Foundry Superfund Site – Decades in the Making, Saint Regis Mohawk Tribe Remediation and Restoration Program, March 24, 2021
• Fourth Five-Year Review Report: GM Massena Central Foundry Superfund Site, U.S. EPA Region 2, 2020
• St. Lawrence River Environment Natural Resource Damage Assessment: Restoration and Compensation Determination Plan and Environmental Assessment, Natural Resource Trustees of the St. Lawrence River Environment, 2013
• Mohawk Uplands Remedial Action Work Plan, GM Worldwide Facilities Group, 2007

November 2023