NPDES Update: Weathering the Storm

July 2007 » Feature Articles
A new MS4 Program Evaluation Guide describes how an EPA/state inspector should prepare for an audit and includes a significant amount of information about the different topics to address and questions an inspector should ask.
John Kosco, P.E., CPESC

A new EPA guide helps municipalities and their consultants prepare for stormwater program audits.

Over the past eight to 10 years, the U.S. Environmental Protection Agency (EPA) and some states have levied significant fines for noncompliance of National Pollution Discharge Elimination System (NPDES) stormwater permitting requirements at construction sites. The most famous of these is probably the enforcement case against Wal-Mart in 2004. The company paid a $3.1 million civil penalty for stormwater construction-site violations in multiple states. However, many other examples of stormwater enforcement at construction sites exist, including large penalties for the California and Idaho departments of transportation (DOT) and a $2 million penalty for a private landowner in Hawaii.

Auditors are on the prowl for storm drain inlets receiving muddy water from uncontrolled construction sites. Photo: Charlie MacPherson


EPA’s enforcement focus has started to turn toward municipalities that implement stormwater programs. In May 2006 Dallas, Texas, agreed to spend more than $3.5 million to improve its stormwater program by hiring key staff, inspecting hundreds of industrial and construction sites, improving maintenance of its storm drain system, and constructing wetlands to filter stormwater runoff. In October 2005 the Hawaii DOT paid a $1 million penalty and agreed to spend an additional $50 million over five years to correct stormwater violations associated with its municipal separate storm sewer system (MS4) permit.

To determine the compliance status of municipal stormwater programs, EPA has been conducting on-site audits of MS4 programs for more than five years now. For example, EPA Region 9 (which covers California, Nevada, Arizona, and Hawaii) has conducted more than 40 audits of municipal stormwater programs and has posted many of these reports online (available at

In January 2007 EPA released a field-test version of its MS4 Program Evaluation Guide (available at and click on MS4) for EPA regional and state inspectors to use when conducting on-site audits. At nearly 200 pages, the guide describes in detail how an EPA/state inspector should prepare for an audit and includes a significant amount of information about the different topics to address and questions an inspector should ask.

Under contract to EPA, Tetra Tech, Inc., has conducted on-site audits of more than 140 municipal stormwater programs. Tetra Tech also developed the MS4 Program Evaluation Guide and is training state and EPA staff on how to conduct municipal stormwater audits. This article summarizes this work and describes how municipalities and consultants can use the audit process to improve stormwater programs.

Conducting self-audits
If you represent a municipality or are a consultant hired to help municipalities implement a stormwater program, the EPA guide presents an opportunity to assess your stormwater program against EPA expectations. A self-audit can prepare you for an upcoming EPA audit or simply help identify potential weaknesses in your stormwater program. Regardless of the reason for doing a self-audit, there are several basic steps to take in conducting one:

EPA’s MS4 Program Evaluation Guide addresses the following NPDES stormwater program components:

  • program management
  • public education and participation
  • MS4 maintenance activities
  • construction activities
  • post-construction activities
  • industrial/commercial facilities
  • illicit discharge detection and elimination
Review your NPDES permit requirements—EPA will focus primarily on the specific requirements in your NPDES permit. Review your NPDES permit to determine if all requirements are being met. Make sure you have documentation, where necessary, to demonstrate compliance. Many NPDES permits issued to municipalities are fairly non-prescriptive but require the development and implementation of a stormwater management program.

Review your stormwater management program (SWMP) planning document (Plan)—Similar to a construction site’s stormwater pollution prevention plan (SWPPP), a SWMP Plan is a municipality’s description of the programs and practices it will use to comply with the NPDES stormwater permit. Review the SWMP Plan to assess whether any activities are not being implemented or if the SWMP Plan needs to be amended. The self-audit should focus on the stormwater management program components listed in Chapter 4 of the MS4 Evaluation Guide.

Using EPA’s guide to prepare for an audit
Believe it or not, there are actually some potential benefits to being audited by EPA. For municipalities that have had little interaction with EPA, the audit provides an opportunity to educate your EPA auditor about the unique conditions and concerns in your municipality. The audit is also an opportunity to solicit feedback from your EPA auditor to clarify issues in the permit, determine the level of effort expected for different activities, or address other questions. Finally, the audit will allow you to get a better handle on your SWMP’s weaknesses (for better or for worse!).

If you find out that you are being audited, you should first make sure that all records related to the implementation of your SWMP and compliance with your NPDES permit are organized and easily accessible. The EPA auditor will likely need to see many of these records, and a proactive approach will save time. If possible, conduct a quick self-audit to try to assess any potential weaknesses. It is always better to acknowledge a weakness and describe how you’re planning to correct it than to be caught off-guard about a potential problem. Brief your management and staff on what to expect during the audit and how to respond to questions, and make sure all appropriate staff are available during the audit. Finally, have a stormwater expert walk through each of the municipality’s maintenance facilities (such as its fleet maintenance facility) before the EPA audit to identify any stormwater problems.

There are a number of things you can do during the audit to make the process go more smoothly. First and foremost, be honest and answer the EPA auditor’s questions. Also, don’t be afraid to ask questions of the EPA auditor (What are your expectations for this permit requirement? What are others doing to address this problem?), and try to educate the auditor about your municipality and the stormwater issues you face. Do not try to hide obvious weaknesses and be open to constructive criticism—this is an audit, so the EPA auditor will likely find things that need to be improved.

Common findings from past audits
Listed below are the 10 most common findings from the 140 municipal stormwater audits that Tetra Tech has conducted under contract to EPA:

1) Inadequate maintenance yard best management practices (BMPs): By far, the most prevalent program deficiency noted during the audits was the lack of appropriate BMPs at municipally owned and operated maintenance facilities. Problems included unprotected storm drains, lack of containment for potentially polluting materials, lack of spill-control measures, and generally poor housekeeping. Often evidence was found of spills that had entered storm drains.

2) No SWPPPs developed for maintenance yards: Many of the audited permittees had not developed SWPPPs for their maintenance yards. Maintenance yards often include auto-maintenance shops, chemical-storage areas, truck-washing facilities, refueling stations, and other facilities and activities that can pose a threat to water quality. Therefore, a plan should be in place that identifies potentially polluting locations and activities, specifies BMPs for each, and outlines spill-control and response measures.

3) No stormwater planning document: A number of municipalities had not developed a SWMP Plan or other document that describes the different activities of the program and includes standard operating procedures and other details. A master planning document that describes current program activities and future goals helps municipalities focus their energies in implementing the stormwater program.

4) Not assessing measurable goals: One important element that is commonly described in the permit or SWMP but was often lacking in audited programs was a clear method for evaluating program effectiveness. Measurable goals are required by EPA for small, municipal stormwater programs and are recommended for all municipal stormwater programs; however, the audits found that many programs either did not develop measurable goals, or had nonspecific goals.

5) Inadequate legal authority: Some municipalities lack adequate legal authority to implement one or more elements of their program. This could have resulted from a number of factors, including lack of political support from elected officials, inability to enforce ordinances adequately, or lack of clear authority in existing ordinances on stormwater violations.

6) Inadequate frequency of inspections: Many municipalities were lax in performing inspections and enforcing their construction or industrial stormwater ordinance(s).These municipalities had no or too few inspectors dedicated to addressing stormwater concerns, and they did not train inspectors in other departments, such as pretreatment, fire safety, or health department inspectors, to look for stormwater violations.

7) Inadequate construction site erosion and sediment control program: Some municipalities have construction programs that focus exclusively on erosion and sediment controls without consideration of other pollutants (such as concrete washouts or fuel) that are commonly found at construction sites. In other cases, inspectors were performing inspections inadequately, using drive-by inspection techniques that would not identify problems with individual BMPs (such as design flaws or poor maintenance).

8) Inadequate BMPs at public construction sites: Some municipalities do not apply the same plan approval and inspection procedures at public, capital improvement projects as they do for private development projects. In several cases, this discrepancy led to inadequate implementation of construction BMPs at publicly owned construction sites. Municipalities should hold their own project proponents and contractors to the same standards as private construction operators and developers.

9) Failing to train staff: Lack of training for personnel was another common finding. Many times when street or park maintenance crews were observed working in the field, BMPs were either inadequate or absent, and storm drains were unprotected. Stormwater-related training should be offered to all staff involved with spill response, those handling materials that could enter storm drains, and street crews who can spot spills or illicit discharges while they go about their daily routine in the permit area.

10) Poor tracking of compliance-related activities: Some municipalities fail to track their compliance-related activities and, therefore, are unable to demonstrate that such activities were performed. For example, municipalities with poor inspection recordkeeping will likely have problems documenting the compliance status of industrial facilities or construction sites within the municipality.

Self-auditing of stormwater management programs can help municipalities determine permit compliance for reporting purposes, assess the effectiveness of their SWMP, and help them to better allocate resources. In addition, as EPA now is beginning to turn its enforcement focus to municipal stormwater programs, conducting a self-audit can help municipalities identify potential problems that will help them "weather the storm" if they are audited by EPA.

John Kosco, P.E., CPESC, is a principal engineer with Tetra Tech, Inc., in Fairfax, Va. He can be reached via e-mail at


More resources for stormwater professionals

Stormwater professionals may be interested in checking out the following valuable guidance documents:

Guidance for Municipal Stormwater Funding
This document was developed by the National Association of Flood and Stormwater Management Agencies under a grant provided by the EPA. Visit here to download this resource. Date Published: January 31, 2006

Illicit Discharge Detection and Elimination: A Guidance Manual for Program Development and Technical Assessments
This Center for Watershed Protection’s comprehensive manual outlines practical, low-cost, and effective techniques for stormwater program managers and practitioners. It provides valuable guidance for communities and others seeking to establish Illicit Discharge Detection and Elimination programs. Visit the Center for Watershed Protection to download this document. Date Published: October 1, 2004

Developing Your Stormwater Pollution Prevention Plan: A Guide for Construction Sites (Interim)
This interim guidance document is intended as a helpful reference for construction site operators who must comply with an NPDES stormwater permit. It describes the SWPPP development process and provides helpful guidance and tips for developing an effective SWPPP. (Note: Final edits are pending on this interim document.) A customizable SWPPP template and sample inspection report (in Microsoft Word format) are also available. Visit here to download the document.


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