Stormwater Permit Basics

Regulatory History | MS4s | General Permits | Learn More

Regulatory History

In 1990, the EPA adopted federal regulations requiring cities with more than 100,000 population and 11 categories of industrial activities to obtain stormwater discharge permits under the NPDES system. These regulations came from concern over pollutants in large urban areas that enter local waterways. The EPA stormwater permit program only controls urban stormwater pollution, not flooding. 1990 “Phase I” rulemaking resulted in two types of “General” permits for stormwater: a “multi-sector general permit” to address Phase I industrial activities (OKR05 permit in Oklahoma), and a general permit for construction sites over five acres (OKR10 permit in Oklahoma).

In September 1997, The U.S. Environmental Protection Agency (EPA) delegated its stormwater permitting authority to the Oklahoma Department of Environmental Quality (DEQ), but EPA continues to have final oversight in Oklahoma.

Following implementation of Phase I permits, in 1999, EPA adopted “Phase II” stormwater regulations that required smaller cities with “urbanized areas” and additional cities as designated by EPA/DEQ to obtain a stormwater permit. The Phase II general permit imposes the same general requirements on each of these small cities instead of imposing individual permits on them. Phase II regulations also addressed small construction sites: between one and five acres.

The main body of federal regulations governing urban stormwater pollution are found in Title 40, Part 122 of the Code of Federal Regulations (40 CFR Part 122). Oklahoma Statutes have adopted the federal stormwater regulations by reference. The main body of state stormwater rules are found in Title 252, Chapter 606 of the Oklahoma Administrative Code (OAC 252:606).

Municipal Separate Storm Sewer Systems (MS4s)

MS4s can be municipalities, counties, universities, military bases, or government organizations that have their own storm sewer systems in place. Oklahoma separates Phase II MS4s into three categories: Category 1 serves a population of less than 10,000 within an urbanized area, Category 2 serves a population between 10,000 and 50,000 within an urbanized area OR 10,000 to 100,000 with a density of 1,000 people per square mile, and Category 3 serves a population of 50,000 to less than 100,000 within an urbanized area. Category 3 MS4s have the most permit requirements, while Category 1 MS4s have the least.

Municipal permittees must develop strategies to identify and control pollutants from sources that are often difficult to manage, such as residential properties, vehicles and transportation corridors, and from illegal dumping of wastes directly into storm drains and creeks. The stormwater program relies upon public education to encourage changes in behavior to reduce urban pollution from many urban sources.

Only three MS4s (Tulsa, Oklahoma City, and ODOT) are permitted under Phase I individual permits in Oklahoma, while 52 small MS4s are permitted under Phase II OKR04 general permits.

Oklahoma’s General Permits

The Oklahoma DEQ issues three types of stormwater general permits: OKR04 for small municipal stormwater permittees, OKR05 for industrial activities, and OKR10 for construction activities. Coverage under each is obtained by submitting an application called a Notice of Intent (NOI), and preparing a Stormwater Pollution Prevention Plan (SWP3) for OKR10 and OKR05 coverage, and a Stormwater Management Program (SWMP) document for OKR04 coverage.

Each of the 3 stormwater general permits in Oklahoma have a 5-year update cycle. About 18 months before the permit expiration date, DEQ begins a reauthorization process that updates permit content to meet existing EPA requirements and add improvements. If a general permit expires before getting reauthorized, existing permittees continue to operate under the expired permit until the reauthorization process is completed.

Learn more: