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For the past several years, EPA has been developing “technical guidance” to add to the December 2003, EPA Watershed-Based National Pollutant Discharge Elimination System Permitting Implementation Guidance [EPA 833-B-03-004]. This “technical guidance” expands on the information in the Implementation Guidance and also addresses many comments received during the public review phase of the Implementation Guidance. During the public review process, many commenters requested more detailed information on how to produce watershed-based permits and how to address specific situations that were considered beyond the scope of basic implementation processes. The decision was made to address these issues in future guidance and that is what is done through this new guidance.

The new guidance is made up of three distinct pieces that recognize there is no one single approach. The watershed approach is characterized by the use of a dynamic process to identify and assess problems holistically and implement site-specific solutions to achieve watershed goals. Therefore, the process for integrating the NPDES permitting program into a larger watershed management system means developing and utilizing a watershed-based analytical approach to coordinate NPDES activities with other water quality activities. A watershed-based analytical approach is the groundwork data collection and analysis conducted to support the development and issuance of NPDES permits that consider the diverse pollutant sources and stressors located within a defined geographic area (i.e., watershed boundaries). The primary difference between a watershed permitting analytical approach and the more common historical approach to permitting is that the watershed permitting analytical approach considers the impact of multiple pollutant sources and stressors, including nonpoint source contributions. In contrast, the historical approach simply uses an aggregate background load. A watershed permitting analytical approach also considers watershed goals throughout the permitting process.

The conclusions reached through the watershed-based analytical approach are then implemented through a broad range of possible NPDES implementation options to achieve watershed goals. These options extend beyond the traditional approach of developing and issuing a single NPDES permit to an individual point source discharger. This broader view of NPDES implementation options is referred to as the NPDES watershed framework, and the NPDES watershed framework serves as a structure to manage implementation of the NPDES program on a watershed basis. The framework provides a variety of permitting options and tools that can be used to implement a watershed approach. The specific permitting options and tools used in the framework will depend on the characteristics of the watershed and the permitting context.

One implementation option used in the Watershed framework is “Promoting Natural Infiltration through Low Impact Development, Green Infrastructure and Smart Growth. Innovative techniques that promote natural infiltration are increasingly considered as alternatives to conventional approaches to managing runoff. Techniques under the umbrella of LID/green infrastructure focus on using small, cost-effective landscape features, such as rain gardens, permeable pavement, and green roofs, that allow a developed site to maintain its predevelopment hydrology by retaining rainfall on site. EPA has highlighted opportunities to increase the development and use of these green infrastructure techniques in water program implementation in a memorandum from Assistant Administrator for Water, Benjamin H. Grumbles, to the EPA Regional Administrators. The memorandum notes that, “green infrastructure can be both a cost effective and an environmentally preferable approach to reduce stormwater and other excess flows entering combined or separate sewer systems in combination with, or in lieu of, centralized hard infrastructure solutions” (Grumbles 2007).

Another approach that promotes natural infiltration is smart growth, a type of growth management strategy that emphasizes the preservation of open space and redevelopment of urban areas as opposed to new development in outlying areas. Preserving open space and undertaking redevelopment promote natural infiltration by limiting the spread of impervious surfaces as well as promoting the preservation of an area's natural hydrologic function. For more information about smart growth and LID, visit EPA's web pages at and, respectively. Resources on LID and smart growth are available from the Low Impact Development Center at and Smart Growth Online at

This presentation will further discuss the concepts of a watershed permitting analytical approach and an NPDES watershed framework, including several permitting tools and options that a framework may include. Specifically, the presentation will describe the set of tools EPA has developed that are the new “technical guidance.” The set of tools include three:

First is the Framework: This piece includes three appendices that contain forms to help NPDES authorities

Appendix A: Stakeholder Involvement in a Watershed Permitting Analytical Approach and an NPDES Watershed Framework

Appendix B: Watershed Data Gap Assessment Worksheet

Appendix C: Keep Water Out Of Sewer Systems Tool Instructions and Form

Second is the Guide: This piece includes 2 appendices that contain forms to help NPDES Authorities in implementing a watershed-based permitting approach

Appendix D: Example Supplemental Effluent Limit Table

Appendix E: Sample Watershed-based Permit DMRs

Third are the Case Studies: These case studies illustrate a variety approaches implemented as part of an NPDES watershed framework including, in some instances, development of a multisource watershed-based permit.

The presentation will also highlight EPA's current activities in to assist NPDES permit writers and permittees throughout implementation of a watershed approach. This guidance builds on the existing Policy and Implementation Guidance that are already available to the public. Finally the presentation will discuss one or more in a series of watershed-based permitting case studies to highlight some real-world examples of implementing an NPDES watershed framework and to illustrate the concepts presented in the guidance. These case studies illustrate a variety approaches implemented as part of an NPDES watershed framework including, in some instances, development of a multisource watershed-based permit.
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Document Type: Research Article

Publication date: 01 January 2008

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