An NPDES stormwater audit is an inspection conducted to ensure that a facility or site is complying with the terms and conditions of its National Pollutant Discharge Elimination System (NPDES) permit for stormwater discharges. The NPDES program is administered by the U.S. Environmental Protection Agency (EPA) to regulate discharges of pollutants from various sources into water bodies.

Facilities that require NPDES stormwater permits include:

  • Industrial facilities
  • Construction sites disturbing one acre or more of land
  • Municipal Separate Storm Sewer Systems (MS4s)

An NPDES stormwater audit typically involves the following steps:

Reviewing the facility’s NPDES permit and Stormwater Pollution Prevention Plan (SWPPP). The SWPPP is a document that outlines the measures the facility will take to prevent pollutants from entering stormwater runoff.

Inspecting the facility or site to verify that the Best Management Practices (BMPs) described in the SWPPP are in place and functioning properly. Common BMPs for stormwater management include erosion control measures, sediment traps, detention ponds, and oil/water separators.

Records of inspections, maintenance, and training – The facility should be able to demonstrate that it is regularly inspecting its BMPs, performing maintenance as needed, and training its employees on stormwater pollution prevention procedures.

The purpose of an NPDES stormwater audit is to:

  • Identify any potential or actual violations of the NPDES permit
  • Help the facility or site improve its stormwater pollution prevention practices
  • Reduce the amount of pollutants discharged into water bodies

Who can conduct an NPDES stormwater audit?

  • Qualified inspectors employed by the EPA or a state environmental agency
  • Certified inspectors employed by a private company

How often should NPDES stormwater audits be conducted?

  • The frequency of inspections will vary depending on the type of facility or site and the nature of its activities.
  • Industrial facilities are typically required to conduct inspections at least quarterly.
  • Construction sites are typically required to conduct inspections at least once a week during active construction and after every major rain event.

What are the consequences of failing an NPDES stormwater audit?

Facilities that fail an NPDES stormwater audit may be subject to enforcement actions, such as fines or penalties. The facility may also be required to take corrective actions to address the identified violations.  By complying with the requirements of their NPDES permits, facilities and sites can help to protect water quality and reduce pollution in our waterways.

Stormwater runoff is rainwater or melted snow that flows over land and eventually into bodies of water. It can pick up pollutants along the way, such as oil, grease, sediment, and fertilizers. These pollutants can harm water quality and aquatic life.

There are two main types of stormwater discharge: Direct and Indirect.

Direct discharge occurs when stormwater runoff flows directly into a body of water, such as a river, lake, or ocean, without any treatment. This can happen in urban areas where there are a lot of impervious surfaces, such as roads and parking lots, that prevent stormwater from infiltrating into the ground.

Indirect discharge occurs when stormwater runoff flows into a municipal sewer system, which then treats the wastewater before discharging it into a body of water. Indirect discharge is more common than direct discharge in most developed areas.

More Best Management Practices (BMPs)

There are a number of BMPs that can be used to reduce stormwater pollution. These include:

  • Green infrastructure practices, such as rain gardens, bioswales, and green roofs, which can help to infiltrate stormwater into the ground.
  • Low impact development (LID) practices, such as permeable pavements and disconnected downspouts, which can also help to reduce stormwater runoff.
  • Good housekeeping practices, such as sweeping up litter and properly disposing of hazardous waste, which can help to prevent pollutants from entering stormwater runoff.

There are two primary categories of stormwater inspections, each serving distinct purposes:

  1. Compliance Inspections:

Ensuring adherence to regulations is the main focus of compliance inspections. These are typically conducted by regulatory bodies like the Environmental Protection Agency (EPA) or local authorities at construction sites or industrial facilities. Inspectors meticulously examine the site to verify that stormwater management practices comply with the regulations set forth in permits. This helps prevent pollutants from entering nearby waterways through stormwater runoff.

2. Routine Inspections:

Proactive maintenance is the cornerstone of routine inspections. Often performed by site managers or designated personnel, these inspections aim to identify and address minor issues before they snowball into major problems. By regularly checking the site’s condition and ensuring proper maintenance of stormwater control measures, these inspections help maintain a healthy stormwater system and minimize the risk of pollution.

Beyond these two main categories, targeted inspections can be conducted to address specific concerns. For instance, if a particular area on a construction site has a history of erosion problems, an inspector might conduct a targeted inspection focusing solely on that area to identify the root cause and implement corrective measures.

Permits and Audit

An NPDES permit is typically a license for a facility to discharge a specified amount of a pollutant into a receiving water under certain conditions. Permits may also authorize facilities to process, incinerate, landfill, or beneficially use sewage sludge. The two basic types of NPDES permits issued are individual and general permits.

  • An individual permit is a permit specifically tailored to an individual facility. Once a facility submits the appropriate application(s), the permitting authority develops a permit for that particular facility based on the information contained in the permit application (e.g., type of activity, nature of discharge, receiving water quality). The authority issues the permit to the facility for a specific time period (not to exceed five years) with a requirement that the facility reapply prior to the expiration date.
  • A general permit covers a group of dischargers with similar qualities within a given geographical location. General permits may offer a cost-effective option for permitting agencies because of the large number of facilities that can be covered under a single permit.

The audit also includes measuring key performance indicators (KPIs) such as completed capital improvement and retrofit projects, septic tank phase out, maintenance activities, load reductions achieved through street sweeping and roadway litter removal, structural control inspection and maintenance, and BMP effectiveness assessment.

​The MS4 Audit process is conducted by Departments of Environmental Protection to comprehensively evaluate and assess compliance with permit conditions, verify the accuracy of information submitted by permittees, and obtain information to support the permitting process.

The audit process includes notification and preliminary documentation request, formal audit, report of findings, compliance assistance, and opportunities for continuous improvement.  The DEPs may take timely and appropriate enforcement actions if needed.

MS4 Audit Preparation

• It’s not if, but when.

• The Departments of Environmental Protection (DEP) will conduct an MS4/NPDES Permit audit sometime in the 5-year permit cycle.

• Make sure that you are prepared throughout the permit cycle:

-Regulatory authority

-Mapping

-Documentation

-Effective SWMP

-SOPs

-Training

-Funding

-All other permit requirements 

Determine key personnel that should participate:

-Executive level

-Organizational chart for all permittees

-Staff

◦ SOP interviews

◦ Site inspections

◦ Permittee facilities with Stormwater Pollution Prevent Plans

Our records management software system, MyMomentum™, can assist you in maintaining the required compliance records needed to satisfy a compliance inspection and to streamline requirements for permittee BMP audits. To learn more about how MyMomentum™ can simply and affordably help you facilitate your records and training management, click the link to view the video! https://buff.ly/3d53MEN

Spencer-SHE has been providing Safety, Health, and Environmental Compliance Guidance since 1980. Our team does stormwater sampling and Stormwater Permit Compliance and Sampling Protocols training. Contact us to assist with the compliance of your stormwater permit.

Sources: 

https://archive.epa.gov/compliance/resources/publications/assistance/sectors/web/pdf/myer2_stormwater.pdf

https://www.florida-stormwater.org/assets/MemberServices/Seminars/2022/5-How_%20to_Prepare_for_Your_Audit_Carr.pdf

https://www.epa.gov/npdes/about-npdes#overview

https://johnscreekga.gov/departments/stormwater-division/ (photo)