Industrial Pretreatment Program



The goal and purpose of the City of Chico Industrial Pretreatment Program is to protect public environmental health and welfare and to maintain water quality through protecting the Water Pollution Control Plant from industrial discharges that could interfere with its operations. Operated under a State of California-administered, United States Environmental Protection Agency (USEPA) National Pollutant Discharge Elimination System (NPDES) permit, the City of Chico water pollution control plant treats wastewater and returns it to the environment via the nearest state/federal receiving waters of the Sacramento River.

The federal government (USEPA), through the Clean Water Act of 1977, requires a city’s Water Pollution Control Plant to develop an Industrial Pretreatment Program if the plant’s dry weather capacity exceeds five (5) million gallons per day (MGD), receives industrial user pollutants that could pass through the plant or interfere with the plant operations or otherwise violate Pretreatment Standards. To prevent industrial sewer discharges that could potentially harm the biological treatment factors of the treatment plant, the pretreatment program is tasked with overseeing discharges to the plant through a set of control mechanisms, or permits.

Industrial Users

Significant Industrial Users discharge a quantity or quality of industrial discharge that could present potential problems to the Water Pollution Control Plant. These industries are characterized as:

Significant, Non-categorical Industrial User discharges greater than or equal to 25,000 GPD of industrial process wastewater (excluding boiler blow-down and non-contact cooling water).

Categorical Industrial User discharges industrial wastewater of categorical processes as codified in 40 CFR Chapter I, Subchapter N, Parts 405-471 of the Federal Register.

Non-Significant Categorical Industrial User (NSCIU)-As part of EPA’s Pretreatment Streamlining Rules, an NSCIU may discharge no more than 100 GPD of categorical industrial process wastewater provided that it meets federal and state Pretreatment Standards. This category allows those industrial users that are smaller, to have fewer reporting requirements than a larger Categorical Industrial User.

Non-significant, non-categorical Industrial User discharges less than 25,000 GPD of industrial process wastewater and may be included in a Pollution Prevention Program.

Pollution Prevention

Food Service Establishments (FSEs) and Grease Interceptors

The City of Chico requires grease interceptors [15.40.030 Interceptors] for restaurants and other FSEs with few exceptions. Contact us if you think you are exempt from a grease interceptor.

The Gravity Grease Interceptor (GGI) should be a minimum 750-gallon capacity, require a sample box with the installation, and be serviceable by manufacturer’s specifications/recommendations. Alternatively in the case that the facility footprint will not allow for the placement of a Gravity Grease Interceptor, an appropriately-sized Hydromechanical Grease Interceptor (HGI) or similar may be approved by City personnel. The Hydromechanical Grease Interceptor should have a certified minimum 20 GPM flow-rating and 40-pound capacity.

Gravity Grease Interceptor

Hydromechanical Grease Interceptor

California Plumbing Code (CPC) Chapter 10 contains the interceptor sizing criteria based on Drain Fixture Units (DFUs) connected to the GGI or HGI. California Plumbing Code Chapter 7, in particular, discusses DFUs for the Gravity Grease Interceptor.

Dental Offices- EPA final rules for dental amalgam were promulgated June 14, 2017. The rules entail a one-time compliance report for new dental offices that have amalgam waste. Amalgam separators must be installed unless an amalgam separator existed at that facility prior to June 14, 2017. June 14, 2027 is the grandfather date for existing amalgam separator installations. After that date, a best available technology (BAT) replacement should be installed. Click here for Frequently Asked Questions on the Dental Office Category Rule.

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