Groundwater Discharges

Groundwater discharge sites receive wastewater derived from any combination of residential (sewage), commercial and industrial sources; therefore, the wide range of consumer products available to homes, businesses or industrial use that contain PFAS and come into contact with, or are deposited into, the wastewater stream from these sources can end up being discharged at these sites.

The NHDES Groundwater Discharge program regulates the discharge of wastewater to the ground or groundwater for all non-domestic wastewater and domestic wastewater with discharge volumes that exceed 20,000 gallons per day. Non-domestic wastewater discharges commonly occur at businesses and industrial facilities, whereas large-volume domestic wastewater discharges commonly occur at publicly owned wastewater treatment plants.
 
Detailed information about the Groundwater Discharge program, including applications, forms and permits can be found at the NHDES Groundwater Discharge webpage. 

PFAS monitoring at Groundwater Discharge Permit sites

PFAS are monitored at groundwater discharge permit sites through a groundwater monitoring well network, which is established around each permitted site to monitor effects of the wastewater discharge on groundwater. The monitoring well network at a discharge site commonly includes many monitoring wells that are sampled on a fixed schedule each year and analyzed for various parameters. For most groundwater discharge sites with a permit, PFAS samples are collected from the monitoring well network once per year, or once per 5-year permit cycle. For some permits, the treated wastewater (effluent) is additionally sampled prior to its discharge at the site and analyzed on a specified schedule for various parameters. The groundwater discharge permit issued for the site assigns the sampling locations, the sample parameter list for each sample location, and the frequency of sample collection for the monitoring network.

Responding to PFAS detections

When PFAS are detected in a site’s groundwater monitoring well network at concentrations that exceed standards, the response differs by type of permittee as follows:

• For discharge permits issued to a privately owned business or industrial facility:
  • The facility (permit holder) shall complete a receptor survey of all possible users of groundwater within 1,000 feet of the discharge site, sample groundwater of those users for PFAS, and install PFAS treatment for any party with PFAS impacted groundwater.
  • The facility shall conduct a product inventory of all chemicals used at the facility for the presence of PFAS and find alternative products to use as replacement for any PFAS-containing products.
• For discharge permits issued to a publicly owned wastewater treatment facility:
  • The facility (permit holder) shall complete a receptor survey of all possible users of groundwater within 1,000 feet of the discharge site, sample groundwater of those users for PFAS, and install PFAS treatment for any party with PFAS impacted groundwater.
  • The facility shall sample its treated wastewater for PFAS and assess if high levels of PFAS are entering the wastewater treatment plant.
  • The facility shall conduct sampling for PFAS from various locations within the sewer collection system to identify customers that may be discharging high levels of PFAS into the sewer system and require those customers to remove PFAS from their wastewater prior to discharging to the sewer system.