Water Protection Program fact sheet
Division of Environmental Quality Director: Ed Galbraith

Oil water separators are mechanical wastewater treatment devices that remove oily and greasy contaminants from process wastewater or stormwater runoff. The Missouri Department of Natural Resources has a general permit (MO-G14) for the discharge from these devices. The purpose of this bulletin is to discuss MO-G14 requirements for oil water separators utilized in the manner describe in example 1 of the below list. Oil water separators described in examples 2, 3, and 4 either require a site-specific permit or may not be regulated by the department.  

Oil water separators are used at sites in the following ways:

The original 1948 Federal Water Pollution Control Act, now known as the Clean Water Act (CWA), has seen many changes.  Among these changes were the 1972 amendments, which included the establishment of the National Pollution Discharge Elimination System (NPDES) created in Section 402 of the federal Clean Water Act. "NPDES prohibits [discharges] of pollutants from any point source into the nation's waters except as allowed under an NPDES permit." The Clean Water Act amendments of 1987 included the regulation of certain stormwater classes by NPDES permitting.

Through the NPDES permit program, the department has received authorization to regulate point sources that discharge pollutants into waters of the state. Point sources are generated from a variety of municipal and industrial operations, including treated wastewater, process water, cooling water, and stormwater runoff from drainage systems. The NPDES Stormwater Program has been in place since 1990 and regulates discharges from municipal separate storm sewer systems (MS4s), construction activities, industrial activities, and those designated by the Environmental Protection Agency due to water quality impacts.

Missouri Industrial Permits
The EPA delegated authority for the NPDES permitting program to the department in 1974. Although the federal government oversees and reviews the Missouri State Operating Permit program, it is the state that issues and enforces these permits. Missouri’s stormwater regulations are located in 10 CSR-20.6.200. These laws require that permits be issued to certain industrial facilities for their discharges. A permit may be required for discharges of water contaminants to waters of the state or to a Municipal Separate Storm Sewer System (MS4). If the activity does not discharge any water contaminants to either, no permit is needed. If it does discharge water contaminants to one or both or if the industrial activity is listed among the regulated categories and meets certain requirements as outlined in 10 CSR 20-6.200(2), a permit is required. 

An industrial activity may be excluded from stormwater permitting if the activity does not expose materials to stormwater as stated in 10 CSR 20-6.200(1)16. Qualified permit holders as well as new applicants that qualify must submit a completed “No Exemption Certification” form (EPA form 3510-11) to the department. This form is available online at:

Who Needs a MO-G14 Permit?
Stormwater and wastewater regulations use the Standard Industrial Classification (SIC) system to determine if an industry is regulated under the law. This classification system was devised by the U.S. Office of Management and Budget to cover all economic activities. Facilities having SIC codes of 5541 and 4959 may need to apply to the department for a Missouri State Operating Permit MO-G14 to discharge stormwater. These facilities may include service stations, truck stops, vehicle repair shops, body repair shops, parking garages, retail store parking lots, and similar sites associated with vehicle parking, repair, or fueling. It is the responsibility of the owner or operator to apply for a MO-G14 permit.

An MO-G14 permit is not required for facilities that have an oil water separator installed if the facility has an industry-specific general permit that has oil and grease effluent limits that are as protective as MO-G14 oil and grease effluent limits.

Permit Applications and Fees
Facilities applying for MO-G14 for the first time must submit application Form E (MO 780-0795), which can be found at, along with the appropriate fees. After issuance of the permit, fees will be assessed annually. To request a renewal of MO-G14, application Form E must be submitted at least 30 days prior to the expiration of MO-G14 along with appropriate fees. If the facility has any questions concerning fees, the facility needs to contact the appropriate regional office.

Permit Requirements
MO-G14 requires that discharges from oil water separators not violate Missouri water quality standards. Annual sampling and testing of the discharged water is required.

A maintenance schedule must be used by the owner or operator of the oil water separator and records of the maintenance kept. Problems that arise when operating an oil water separator are usually the result of undersized or inadequately maintained oil water separators. The oil and grease caught by the separator must be removed in a timely manner so that the next storm does not wash out the accumulated oil and grease.

Permit Exemptions
Unless required by the department, MO-G14 is not required for any facility that installs an oil water separator voluntarily, (i.e. not required to do so by any state or federal regulation or law) and whose oil and grease originates only from vehicle parking, and/or fueling such as parking lots, gas stations, convenience stores, and truck stops.

Facilities that discharge directly to a combined sewer system with a department approved Long Term Control Plan [10 CSR 20-7.015(10)] or to a publicly owned treatment works that has consented to receiving such a discharge are exempt from permit requirements.

Important Permit Dates
MO-G14 is issued on a five-year cycle. Important dates of each permit are:

Transfer of Permit
A permit may be transferred to a new owner by submitting an Application for Transfer of Operating Permit (MO 780-1517), which can be found at, along with the appropriate fees.

Termination of Permit
General permits may be terminated when activities covered by the permit have ceased and no significant materials are stored in such a way as to come into contact with stormwater. When general permit termination is sought, the permittee must submit Form H, (MO 780-1409), which can be found at

Site-Specific Permit
If requested by the owner or operator, a facility may be covered by a site-specific permit. A site-specific permit takes into account the individual characteristics of the site. In addition, the department may determine that the quality of waters of the state can be better protected by requiring the owner or operator of a facility to apply for a site-specific permit. For questions or guidance regarding the need for a site-specific permit or to begin the application process for a site-specific permit, the facility should contact the appropriate regional office.

Map of Missouri Department of Natural Resources’ Regional Offices
The regional office map is available online at