Wastewater Treatment Plant Groundwater Discharge

The Town's existing Wastewater Treatment Plant is located at 131 Camelot Drive and has been in operation for two decades. As currently permitted, most treated effluent from the Treatment Plant is discharged to directly to Plymouth Harbor via an outfall with the remainder discharged to sand infiltration beds on site. The Town is currently undergoing the permitting process to reverse the prioritization of these two outfalls to discharge primarily to the sand infiltration beds, with the harbor outfall retained for emergency situations.

The existing Treatment Plant went online in May 2002 pursuant to all applicable permitting. The Town completed an extensive Environmental Impact Report (EIR) process through the Massachusetts Environmental Policy Act (MEPA) and received a MEPA certificate in June 1997 (EOEA # 8228). The Treatment Plant has a current Groundwater Discharge Permit from MassDEP for discharge to the sand infiltration beds on site and a NPDES permit authorizing use of the outfall discharge into Plymouth Harbor. 

The current permitting allows an annual average discharge of 1.75 million gallons per day (MGD) of treated effluent to be discharged to Plymouth Harbor via the outfall pipe. Only daily effluent flows in excess of that 1.75 MGD can be conveyed to discharge at the sand infiltration beds adjacent to the Treatment Plant. Discharges to the infiltration beds is limited to an annual average of 0.75 MGD. The current total average daily discharge volume under the Groundwater Discharge Permit is 2.5 MGD with the ability to be increased to 3.0 MGD with prior authorization from MassDEP. The MEPA certificate also identifies the ability to increase authorized total discharge up to 3.0 MGD.

The Town has submitted an Expanded Environmental Notification Form (EENF) to MEPA as the first step in the process to obtain a new Groundwater Discharge Permit from MassDEP to change the discharge prioritization to the sand infiltration beds at the Treatment Plant and increase the total average discharged volume to 3.0 MGD.

In accordance with MEPA requirements, an online consultation session was held on October 4, 2023 to receive advice and comments from agencies, officials, and citizens regarding which environmental issues, if any, are significant for the project. The October 4, 2023 presentation slides can be viewed here (PDF). 

It is important to note that the EENF is only the first step in the regulatory approval process and the project requires the preparation and submittal of an Environmental Impact Report (EIR) with MEPA.