General Permit OKR04: Phase II Small Municipalities
Phase II Permittees | Permit Requirements | Stormwater Management Programs | Minimum Control Measures
Phase II Permittees
In 1999, the U.S. 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 individual permits. The most recent OKR04 Permit was issued by DEQ on June 1, 2021. Permit reauthorization is completed in 5-year cycles, with the next permit scheduled to be released on June 1, 2026. The 2021 permit can be located here.
There are currently 52 regulated Phase II MS4s in Oklahoma under 2021 permitting requirements. These permittees are divided up into three categories depending on population, population density, and urbanized area boundaries. Category 3 MS4s have the most permit requirements, while Category 1 MS4s have the least.
Permit Requirements
The base of compliance with OKR04 is a Stormwater Management Program (SWMP). Each MS4 is required to develop, update, and enforce a written SWMP that includes effective best management practices (BMPs) to control stormwater pollution. A SWMP is ideally a living document, and should be reviewed and updated frequently.
Stormwater Management Programs (SWMP)
The base of compliance with OKR04 is a Stormwater Management Program (SWMP). Each MS4 is required to develop, update, and enforce a written SWMP that includes effective best management practices (BMPs) to control stormwater pollution. A SWMP is ideally a living document, and must be reviewed at least annually.
GCSA developed a SWMP template to aid Phase II permittees in compliance. This template is typically updated with each permit reauthorization cycle, and is available to GCSA members and other permittees.
Minimum Control Measures (MCMs)
A vital part of a SWMP is addressing the six required Minimum Control Measures (MCMs) with effective BMPs and measurable goals for meeting those BMPs. These goals can be measured via progress to completion, a schedule or timeline, or another quantifiable target where applicable. There are six required MCMs, and one optional MCM under the 2021 OKR04, described below. For each of these, the permit contains separate requirements and recommendations.
MCM 1: Public Education and Involvement
Permittees are required to implement a program and distribute information and educational materials to the community and MS4 staff, or conduct outreach activities to promote behavioral changes to reduce pollution in stormwater runoff. Refer to the OKR04 Permit for detailed requirements.
Permit recommendations for MCM 1 include methods that may be employed to meet the permit requirements, such as outreach approaches and potential partner agencies. Refer to the OKR04 Permit for detailed recommendations.
MCM 2: Industrial Stormwater Runoff Control
MCM 2 is only applicable to Category 3 permittees. Category 3 MS4s must implement and enforce a program to prevent or reduce pollutants in stormwater runoff from independently owned industrial facilities that discharge into the MS4. Program requirements must be consistent with OKR05 requirements. Permittees must inspect a specific number of facilities each year to comply. Refer to the OKR04 Permit for detailed requirements.
MCM 3: Illicit Discharge Detention and Elimination
Permittees are required to implement and enforce a program to detect and eliminate illicit discharges such as illegal dumping and on-site sewage disposal into a storm drain. The OKR04 permit requires dry weather field screening (DWFS) to identify non-stormwater flows and the implementation of BMPs to counteract these discharges. Refer to the OKR04 permit for detailed requirements.
MCM 4: Construction Site Stormwater Runoff Control
Permittees are required to implement and enforce a program to reduce pollutants in stormwater runoff coming from construction sites in accordance with OKR10. In this program, permittees must perform inspections on constrcution sites. Refer to the OKR04 permit for detailed requirements.
MCM 5: Post-Construction Management in New Development and Redevelopment
Permittees are required to implement and enforce a program to maintain pre-development runoff conditions of newly developed areas. This MCM is most easily addressed via ordinances and construction requirements. Refer to the OKR04 Permit for detailed requirements.
MCM 6: Pollution Prevention/Good Housekeeping for MS4 Operations
Permittees are required to implement and enforce a program that addresses potential runoff pollution sources stemming from municipal operations. This includes reducing pollution from streets, parking lots, maintenance yards, fueling areas, and waste transfer stations, fleet storage facilities, and other operations within the MS4. Refer to the OKR04 Permit for detailed requirements.