EPA's NPDES Phase II Rule requires those undertaking land-disturbing
construction activities, operators of industrial facilities, and operators of
small Municipal Separate Storm Sewer Systems (MS4s) to protect water resources.
MS4 permits call for the development
and implementation of a stormwater
management program that addresses six “minimum control measures” (MCMs).
Implementing these minimum control measures, typically means applying
one or more best management practices (BMPs). Because of site-specific, local,
and regional variability, the BMPs deemed most appropriate for one community may
be vastly different for another community within the same watershed, let alone
in a different part of the state—or a different part of the country!
EPA offers a variety of resources outlining the six MCM requirements, goals of
each, and suggested BMPs that can help achieve results.
MCM 1: Public education &
MCM 2: Public involvement
MCM 3: Illicit discharge detection
MCM 4: Construction site runoff
MCM 5: Post-construction stormwater
management in new development &
MCM 6: Pollution prevention
housekeeping for municipal operations &
DEP manages stormwater through various regulatory programs, including: NPDES
Permit for Municipal Small and Large Separate Storm Sewer System (MS4 Program);
NPDES Permits for Discharges Associated with Construction Activities; and the
Pennsylvania Storm Water Management Act. Details can be found
Pennsylvania’s MS4 Program reflects the six Minimum Control Measures (MCMs) of
the federal program, as discussed
and calls for the application of Best Management Practices (BMPs) to each MCM.
In order to assist municipalities, designers,
developers, and engineers in understanding, developing, and
implementing stormwater management programs, PA DEP
published the PA Stormwater BMP Manual in 2006.
As noted in the
"The Manual is intended to be a
tool to achieve the regulatory standard to protect, maintain, and improve
the Commonwealth’s water resources through comprehensive site planning and
BMP design guidance, while allowing for the continued growth and development
As such, the Manual’s main focus is on BMPs that help meet the requirements of
MCMs 4 through 6. These BMPs are generally classified as “non-structural”
(design and planning techniques that preserve natural systems and hydrologic
functions on a site) and “structural” (more conventional “brick and mortar”
techniques, which may include vegetation and soil-based mechanisms.) The key
distinction between Non-Structural and Structural BMPs is that the former are
intended to prevent stormwater generation, while the focus of the latter is on
mitigating unavoidable stormwater-related impacts.
When it comes to development, the Stormwater Management Program described in the
Manual emphasizes a comprehensive total site design approach. Whether referred
to as “Low Impact Development”, “Conservation Design”, or “Green Design”, this
environmentally sensitive approach to site development and stormwater management
aims to minimize the effect of development on water, land, and air resources.
The use of best management practices, or BMPs, is the primary method of
controlling stormwater discharges and preventing runoff from adversely affecting
water quality. BMPs are a suite of planning processes, development
methodologies, and specific techniques designed to be used in combination to:
- Prevent disturbances to natural systems and hydrologic functions; and
- Minimize the impacts of disturbances where they do occur.
This guidance Manual identifies information on resource planning, techniques for
land development, and concepts and procedures for designing and implementing
performance-based BMPs for managing stormwater for quantity and quality. The
comprehensive planning approach to stormwater management emphasizes reducing the
impacts of development activities through the mitigation process by employing
practices that avoid and minimize potential impacts to watershed resources. The
BMPs are designed to minimize or mitigate for the unavoidable impacts that
development has on watershed resources.
This manual lists various BMPs and design standards, which are acceptable in
Pennsylvania to manage stormwater and prevent pollution of waters of the
Commonwealth. Stormwater management plans and the BMPs designed according to
these standards when properly applied, implemented and maintained, will achieve
the Department’s water quality mandates established in 25 Pa. Code Chapter 93
and required by the federal Clean Water Act, federal NPDES regulations, the
Pennsylvania Storm Water Management Act and the Pennsylvania Clean Streams Law.
The proper utilization and implementation of these BMPs will protect and
maintain existing uses and the level of water quality necessary to protect the
existing uses, and will protect and maintain the water quality of high quality
and exceptional value waters of the Commonwealth.
This Manual Provides:
A standardized process for evaluating site design and BMP selection to
minimize or eliminate the net change in post construction volume, rate and
A standardized approach to measuring pre-construction volume, rate and
quality and post construction site runoff volume, rate and quality.
Standardized specifications for BMPs to manage stormwater to minimize the
net change in post construction runoff volume, rate and quality.
Alternate BMPs, not listed in this manual, that provide the same or greater
level of protection, may also be used to attain the regulatory standard. It is
incumbent on the person proposing the use of alternative BMPs to demonstrate
their effectiveness with appropriate supporting analysis, calculations, test
results or other documentation.
BMP Manual - Introduction
SUMMARY: The Department will ensure that activities and plans approved under its
authority will employ stormwater management plans utilizing best management
practices to control the volume, rate and water quality of post construction
stormwater runoff so as to protect and maintain the chemical, physical and
biological properties of waters of the Commonwealth. These best management
practices must, at a minimum, protect and maintain water resources, preserve
water supplies, maintain stream base flows, preserve and restore the flood
carrying capacity of waters, preserve to the maximum extent practicable the
natural stormwater runoff regimes and natural course, current and cross section
of waters of the Commonwealth, and protect and conserve ground waters and
ground-water recharge areas.