Everything You Need to Know about Wyoming SWPPP and NPDES Permit Requirements

Tyler Whitt
May 5
5 min read

Understanding and implementing a comprehensive Storm Water Pollution Prevention Plan (SWPPP) is crucial for construction activities in Wyoming to protect the state's water quality. The Wyoming Department of Environmental Quality (DEQ) requires SWPPPs for construction projects that disturb one or more acres. The specific requirements can vary depending on the size of the project. The following breaks down the SWPPP requirements for both small and large construction activities based on the Wyoming Small and Large Construction General Permits.

What is a SWPPP?

A SWPPP is a site-specific document that outlines the potential sources of stormwater pollution and details the Best Management Practices (BMPs) that will be implemented to prevent pollution in stormwater runoff. The goal of a SWPPP is to ensure that stormwater discharges do not cause violations of state surface water quality standards.

Small Construction SWPPP Requirements (Disturbing 1 to less than 5 acres)

For small construction activities that disturb at least one acre but less than five acres, or are part of a larger common plan of development that will ultimately disturb at least one but less than five acres, coverage under the Small Construction General Permit (WYR10A000) is required.

Key requirements for small construction SWPPPs include:

SWPPP Preparation: A SWPPP must be prepared before beginning construction activities.
Automatic Coverage: Coverage under this permit is considered "automatic" upon preparation of the SWPPP; a Notice of Intent (NOI) is not typically submitted to the DEQ, and a Letter of Authorization (LOA) is not issued. Sites are required to post a Construction Site Notice detailing project contact information and expected dates of construction.
Pollutant Source Identification: The SWPPP must describe potential pollution sources.
Best Management Practices (BMPs): The SWPPP must detail the BMPs that will be used to prevent stormwater contamination. These measures should be consistent with narrative effluent limits and prevent water quality standard violations.
Site Map: The SWPPP should include a site map indicating areas of disturbance, locations of structural BMPs, and discharge points. Areas with steep slopes or erodible soils should be identified.
Inspections: Required self-inspections must be conducted, and results must be documented. Inspections should be performed periodically to minimize offsite pollutant transport. The standard inspection schedule is every 14 days, but more frequent inspections may be necessary in certain areas.
Maintenance: BMPs must be maintained to address deficiencies in pollutant removal.
Termination of Coverage: Coverage continues until the site is "finally stabilized," meaning areas without permanent structures are revegetated to a uniform 70% of natural cover. Temporary, synthetic erosion and sediment controls must also be removed.
Prohibited Discharges: Certain discharges are prohibited, including concrete washout waters, wash waters from various construction materials, and chemical treatment of stormwater to reduce sediment load.
Conservation Executive Orders: Projects within Sage Grouse Core Areas or Mule Deer and Antelope Migration Corridors must comply with relevant Executive Orders and consult with the Wyoming Game and Fish Department.

Large Construction SWPPP Requirements (Disturbing 5 or more acres)

For large construction activities that disturb five or more acres, or are part of a larger common plan of development that will ultimately disturb five or more acres, coverage under the Large Construction General Permit (WYR100000) is required.

Key requirements for large construction SWPPPs include:

Notice of Intent (NOI) Submission: Operators must prepare a SWPPP and submit it along with a NOI form to the DEQ 30 days before starting construction.
Letter of Authorization (LOA): Discharge is authorized only after submitting a NOI and receiving a LOA from the DEQ.
SWPPP Content: The SWPPP must describe potential pollution sources and the BMPs to be used. It should include site descriptions, control measures, maintenance and inspection procedures, and identification of non-stormwater discharges.
BMP Implementation: BMPs must be installed and maintained to reduce the potential discharge of pollutants. Control measures must be consistent with narrative effluent limits and prevent water quality standard violations.
Site Map: The SWPPP should include site maps detailing the project area and BMP locations. Areas with steep slopes and/or erodible soils should be identified. Discharge points should be shown on the map. Dewatering discharge points must also be added to the map.
Inspections: Operators are required to periodically inspect BMPs. Inspection results must be documented, and necessary changes made to BMPs. The standard inspection schedule is every 14 days, with more frequent inspections in certain areas if needed. Inspections are usually not required during winter conditions with continuous snow cover or frozen ground where melting conditions are absent. Check with your local regulatory authority to confirm before adjusting your inspection schedule.
Maintenance: BMPs must be maintained to ensure effectiveness. Eroded areas must be repaired and stabilized within 7 calendar days of findings.
Termination of Coverage: Coverage continues until the site is "finally stabilized," defined as achieving 70% uniform perennial vegetation cover in areas without permanent structures. Temporary, synthetic erosion and sediment controls must be removed.
Prohibited Discharges: Prohibited discharges include concrete washout and wash waters from various construction materials. Chemical treatment for sediment removal requires detailed information and approval from the Division.
Conservation Executive Orders: Projects within Sage Grouse Core Areas, non-core sage grouse areas, or Mule Deer and Antelope Migration Corridors must comply with relevant Executive Orders and consult with the Wyoming Game and Fish Department, providing letters of consistency with the NOI.
Discharges to Class 1 Waters: Projects with the potential to discharge to Class 1 waters may be subject to a pre-authorization site visit by DEQ personnel, which could delay coverage.
Fees: A permit fee must be submitted with the NOI. Fees are calculated at $200 per year of coverage needed up to a maximum of 5 years or $1,000.

Key Differences Summarized

The primary differences in SWPPP requirements for small versus large construction sites in Wyoming lie in the permitting process and the level of detail expected in the SWPPP and associated documentation. Large construction activities require the submission of a NOI and receipt of a LOA before beginning construction activities, while small construction coverage is generally automatic upon SWPPP preparation and posting of a Construction Site Notice.

Large projects also have more explicit requirements regarding consultation for projects within sensitive wildlife habitats and potential site visits for discharges to Class 1 waters. Both require a comprehensive SWPPP and regular inspections and maintenance of BMPs to prevent stormwater pollution.

For detailed requirements, always refer to the specific general permit for the size of your construction activity issued by the Wyoming DEQ.

Need Help with Your Wyoming SWPPP?

Navigating the intricacies of SWPPP requirements can be time-consuming and complex. Let the experts at Eco Permit Pros take the headache out of the process, giving you back valuable time to focus on your construction project. Our consulting services can help ensure your SWPPP is comprehensive and compliant with all Wyoming DEQ regulations. Contact us today and check SWPPP off your to-do list!

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