NPDES Permit

The NapaSan Code regulates the use of public and private sewers and drains within the NapaSan service area. This includes the installation and connection of building sewers, the installation of sewer laterals, and public sewer main extensions. The Code also provides the fee structure for the installation and connection of sanitary sewers, regulates the discharge of waters and wastes into the public sewer system and provides penalties for the violations of any of these provisions.

National Pollutant Discharge Elimination System (NPDES) Permit

NapaSan has a permit to discharge treated wastewater under the National Pollutant Discharge Elimination System (NPDES). This system, established under the federal Clean Water Act, regulates point source dischargers (wastewater treatment plants, factories) as well as non-point sources (stormwater).

NapaSan’s NPDES permit consists of waste discharge requirements specifying the amount of wastewater that can be discharged, sampling frequency, and the types of testing and monitoring that must be done by NapaSan, and also sets limits of pollutant concentrations. NapaSan’s NPDES permit must be renewed every five years.  The NPDES permit was issued to NapaSan jointly by the U.S. EPA and the San Francisco Bay Regional Water Quality Control Board (RWQCB) and went into effect April 1, 2022.  

Under its NPDES permit effective April 1, 2022, NapaSan is allowed to discharge treated wastewater to the Napa River during the wet season, October 1 through June 30. NSD provides full secondary treatment of wastewater whenever discharging to the river. From July 1 through September 30, the dry season, discharge to the river is prohibited, and wastewater is either stored in the treatment ponds at the treatment plant, or treated to produce recycled water. The recycled water  is used for irrigation by golf courses, business parks, community parks, schools, cemeteries, and vineyards.