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EPA and MassDEP Issue Updated Permit for Wastewater from Pilgrim Facility in Plymouth, Mass.

Contact Information: 
David Deegan (

PLYMOUTH, Mass. – The U.S. Environmental Protection Agency (EPA) and the Massachusetts Department of Environmental Protection (MassDEP) have issued a final permit covering ongoing wastewater discharges at the Pilgrim Nuclear Power Station in Plymouth. While the station permanently ceased generating electricity on May 31, 2019, certain discharges to Cape Cod Bay continue, including non-contact cooling water used to absorb waste heat from the spent fuel pool, process water, and stormwater.

The National Pollutant Discharge Elimination System (NPDES) permit outlines conditions and requirements to protect the aquatic environment of Cape Cod Bay. In all, the Final Permit includes a suite of effluent limitations, non-numeric limitations, and monitoring requirements that represents a significant advancement from the 1991 permit and will ensure that the aquatic community and designated uses of Cape Cod Bay are protected.

The final permit establishes limitations and requirements, consistent with post-shutdown operations, that represent a 92% reduction in volume of cooling water intake and a 98% reduction in heat load as compared to when the plant was generating electricity. In addition, the final permit establishes effluent limitations and monitoring requirements on discharges of miscellaneous “low-volume” type wastes, non-contact cooling water for spent nuclear fuel rods, non-thermal backwash water for biofouling control, and stormwater, including stormwater that accumulates in electrical vaults.

The final permit does not authorize the discharge of spent fuel pool water, stormwater associated with construction activity, or the discharges of pollutants associated with contaminated site dewatering, pipeline and tank dewatering, collection structure dewatering, or dredge-related dewatering. This prohibition includes discharges of pollutants associated with the dismantlement and decontamination of plant systems and structures and the demolition of buildings.

More information on NPDES permits in New England may be found at: