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Stormwater Management and Planning Chapter 1
3.2.1 Construction Site Stormwater Runoff Control
Under the Construction Program, permittees are required to develop, implement, and enforce a pollutant
control program to reduce pollutants in stormwater runoff to their MS4 from construction activities that
result in land disturbance of one or more acres. MS4 permittees frequently extend this requirement to
smaller areas of disturbance if the total site acreage is one acre or larger or if it drains to an
environmentally sensitive area. See Chapter 7 for detailed information on construction BMPs.
3.2.2 Post-construction Stormwater Management
Under the post-construction stormwater
management in new development and
redevelopment provisions, the MS4 General
Permit (CWQCD 2008) requires the permittee to
develop, implement, and enforce a program to
address stormwater runoff from new
development and redevelopment projects that
disturb greater than or equal to one acre,
including projects less than one acre that are part
of a larger common plan of development or sale,
that discharge into the MS4. The program must
ensure controls are in place that would prevent
or minimize water quality impacts. See Chapter
4, Treatment BMPs and Chapter 5, Source
Control BMPs, for detailed information on postconstruction
BMPs.
Redevelopment
The EPA Stormwater Phase 2 Final Rule Fact
Sheet 2.7 states that redevelopment projects alter
the footprint of an existing site or building in such
a way that that there is a disturbance of equal to or
greater than one acre of land.
This means that a "roadway rehabilitation"
project, for example, where pavement is removed
and replaced with essentially the same footprint
would not be considered "redevelopment",
whereas a "roadway widening project", where
additional pavement (or other alterations to the
footprint, pervious or impervious) equal to or in
excess of one acre would be considered
"redevelopment".
Although MS4 general permits have historically
focused on water quality, it is noteworthy that
there has been increased emphasis on reducing stormwater runoff volumes through use of Low Impact
Development (LID) techniques. For example, MS4 permit language for some Phase I municipalities has
also included the following:
Implement and document strategies which include the use of structural and/or non-structural
BMPs appropriate for the community, that address the discharge of pollutants from new
development and redevelopment projects, or that follow principles of low-impact development
to mimic natural (i.e., pre-development) hydrologic conditions at sites to minimize the discharge
of pollutants and prevent or minimize adverse in-channel impacts associated with increased
imperviousness (City and County of Denver 2008 MS4 permit).
Similarly, at the national level, the Energy Independence and Security Act of 2007 (Pub.L. 110-140)
includes Section 438, Storm Water Runoff Requirements for Federal Development Projects. This section
requires:
…any sponsor of any development or redevelopment project involving a federal facility with a
footprint that exceeds 5,000 square feet shall use site planning, design, construction, and
maintenance strategies for the property to maintain or restore, to the maximum extent technically
feasible, the predevelopment hydrology of the property with regard to the temperature, rate,
volume, and duration of flow.
1-10 Urban Drainage and Flood Control District August 2011
Urban Storm Drainage Criteria Manual Volume 3