Wastewater Discharge Permits for Industrial Users

Sewage collection and treatment systems are not designed to treat certain industrial wastes, which can damage sewers and interfere with the operation of treatment plants, or pass through the system untreated, polluting nearby water bodies like the Napa River.

In order to protect the NapaSan’s treatment plant and local water quality, NapaSan regulates the types of waste that can be discharged to our collection system by requiring permits of certain industrial sewer users. Industries and businesses that discharge “non-domestic” waste must get a Discharge Permit from NapaSan, and in some cases must implement Best Management Practices (BMPs) or a pretreatment program to insure that their waste is safe to discharge to the sewer system.

Permit types are described in general below. For more information and to determine the type of permit required by your operation, contact NapaSan’s Engineering Department at 707-258-6000.

Industrial User Permit:

This term applies to any sewer user that discharges non-domestic wastes to the sewer system. A business such as an office that discharges waste only from restrooms or kitchen facilities is not considered an Industrial User. Industrial Users may be required to implement Best Management Practices (BMPs), have regular inspections by NapaSan staff, or meet other requirements as prescribed in the NapaSan Code. Industrial User Permits are issued by the NapaSan’s Engineering Department. Call (707) 258-6000 to request a permit application.

Examples of Industrial Users that must have a permit AND/OR implement BMPs include:
• Automotive repair
• Dental offices
• Food processing
• Photo processors
• Wineries/breweries

Industrial User Discharge Permit Application

Categorical Industrial User Permit:

Categorical Industrial Users (CIUs) are defined under the Clean Water Act, and include industries that discharge wastes containing pollutants that could harm the wastewater treatment system or pass through untreated. This definition also includes any industry which discharges an average of 25,000 gallons per day or more of process wastewater to the sewer system (excluding sanitary, contact cooling and boiler blowdown wastewater).

CIUs must implement pretreatment (pollution control) programs, monitor the water quality of their discharge and submit reports to NapaSan. These requirements are spelled out in the permit.

Examples of Categorical Industrial Users include:
• electroplating shops
• pharmaceutical facilities
• circuit board manufacturers

Special Discharge Permits

Some discharges to the sewer system are temporary and are linked to a specific activity, such as construction water testing or draining a swimming pool. For these types of discharges, the NapaSan Engineering Department issues a Special Discharge Permit which usually specifies a discharge rate and location. Call (707) 258-6000 to request a special discharge permit application.

Groundwater & Surface Cleaning Discharge Permit

Groundwater Permit Application
A Groundwater or Surface Cleaning Discharge Permit allows the temporary (up to one year) connection to the sanitary sewer system to dispose of  treated groundwater or surface cleaning water.

Examples of groundwater or surface water discharges include:
• Gas station groundwater clean up
• Dry cleaner groundwater clean up
• Construction sites
• Parking lot cleaning  

In order to issue a Groundwater Discharge Permit, the District needs to know how much water needs to be disposed (flow) and the estimated time period. The District also requires a water sample to determine if the groundwater can be accepted into the sewer system. The sample must be tested by an independent water quality lab and must meet the local contaminant limits that are called out in the NapaSan Code.

If the sample meets the local limits, it can be accepted for disposal. Sometimes pretreatment will be required (e.g. through activated carbon filter) before the groundwater can be accepted; NapaSan will review the water sample analysis results and let you know if pretreatment is required. After pretreatment, NapaSan will again review water sample analysis to determine if the groundwater can be discharged to the sewer system.

Samples for water quality monitoring are taken quarterly during the duration of the permit (one year) and reported to NapaSan. Fees for Groundwater Discharge Permits are based on the amount of flow and a connection fee. See the Rates & Fees page for more information.  

Wineries & Breweries

The wine and beer industry is an essential part of the Napa Valley. The NapaSan works with wineries and breweries to minimize the impacts of their waste on the treatment system and to keep sewer costs down.

Winery and brewery waste can contain high levels of organic materials and suspended solids – both of which can impact wastewater treatment plant operations. In addition, well over half of all winery waste is in the 2 to 3 month vintage season, from late August through late October. This means that NapaSan needs to work closely with winery customers to develop a pretreatment plan that protects the winery and the wastewater treatment system.

Discharge Permits for wineries and breweries require installation of a flow meter and weekly sampling of the wastewater flow for Biochemical Oxygen Demand (BOD), Total Suspended Solids (TSS) and pH. This information is then forwarded to NapaSan for review to insure that the pH level meets water quality standards. The BOD and TSS data are used for billing purposes. The possibility of exceeding the water quality limits is high for winery and brewery waste, due to the variability in these operations. Additional fees are charged if a discharger’s waste exceeds these limits.

Waste Haulers:

NapaSan accepts waste from licensed waste haulers doing business in Napa County. Waste haulers must apply for a permit through NapaSan’s Engineering Department. Call (707) 258-6000 to begin the permit process.

Waste from the following sources is accepted at the wastewater treatment plant; click here to see the fee schedule:
• Domestic Waste
• Portable Toilets Waste
• Fats, oils and grease (FOG) 
• Treated Waste
• Disinfecting Water Waste


NapaSan's septic and FOG receiving stations are located at the Soscol Water Recycling Facility, at 1515 Soscol Ferry Road, Napa, CA.


Monday – Friday, 7:30 a.m. to 4:00 p.m., excluding holidays. Check here for holiday closures.


NapaSan monitors the waste at the receiving station, checking both which flow and pH levels. The pH value for all wastes discharged to the sanitary sewer is required to be between 6.0 and 9.0. Depending on the waste, a load may require pH adjustment to meet these requirements. Please note that hauled waste should be tested and adjusted to pH prior to entering the Soscol Water Recycling Facility. 

If the pH level of the waste is outside of the accepted limits, this is a violation of the waste hauler permit and discharge is not allowed.

FOG Discharge Permit Application 

Septic Discharge Permit Application Form

Zero Waste Discharge Permit Application