Performance Standards

Pennsylvania’s regulatory standards for post construction stormwater discharges are designed to meet the antidegradation requirements of Chapter 93 Water Quality Standards:

• In Areas Tributary to High Quality and Exceptional Value (Special Protection) Waters—there shall be no degradation of existing or designated stream quality through a change in post construction stormwater runoff volume, rate and quality.
• In Areas Tributary to Waters other than Special Protection—any change in post construction stormwater runoff volume, rate and quality shall not impair existing or designated uses, whichever use is more stringent.

To meet these standards, construction projects should result in no-net-change in stormwater runoff volume, rate or quality from pre- to post-construction conditions. This goal ensures that the chemical, physical and biological properties of receiving waters will not be altered.

The Pennsylvania Best Management Practices Manual provides guidance, options, and tools that can be used to protect water quality, enhance water availability and reduce flooding potential through effective stormwater management. Based on a broad understanding of natural land and water systems, it focuses first on prevention through comprehensive planning and development techniques, and second on mitigation by employing non-structural and structural BMPs. It takes a comprehensive, integrated approach, based on ten basic principles:

1. Managing stormwater as a resource;
2. Preserving and utilizing existing natural features and systems;
3. Managing stormwater as close to the source as possible;
4. Sustaining the hydrologic balance of surface and ground water;
5. Disconnecting, decentralizing and distributing sources and discharges;
6. Slowing runoff down, and not speeding it up;
7. Preventing potential water quality and quantity problems;
8. Minimizing problems that cannot be avoided;
9. Integrating stormwater management into the initial site design process; and
10. Inspecting and maintaining all BMPs.

RESOURCES

Chapter 3 of the Manual provides an in-depth discussion of these comprehensive principles and recommended control guidelines to help municipalities improve their stormwater management regulations.
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Chapter 8 offers a look at widely used methodologies for estimating the total runoff volume, the peak rate of runoff, and the runoff hydrograph from land surfaces under a variety of conditions, and provides a series of worksheets to assist in the preparation, presentation, and review of project data.
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