United States
                           Environmental Protection
                           Agency
                            Office of Water
                            (4203)
EPA 833-F-99-009
April 1999
Fact Sheet 2.7
 vvEPA
Storm Water Phase II
Proposed Rule
Fact Sheet Series

Overview

1.0-Storm Water Phase II
Proposed Rule Overview

Small MS4 Program

2.0 - Small MS4 Storm Water
Program Overview

2.1 - Who's Covered? Designation
and Waivers of Regulated Small
MS4s

2.2 - Urbanized Areas: Definition
and Description
   Minimum Control Measures

2.3 - Public Education and
Outreach Minimum Control
Measure

2.4 - Public Participation/
Involvement Minimum Control
Measure

2.5 - Illicit Discharge Detection and
Elimination Minimum Control
Measure

2.6 - Construction Site Runoff
Control Minimum Control Measure

2.7 - Post-Construction Runoff
Control Minimum Control Measure

2.8 - Pollution Prevention/Good
Housekeeping Minimum Control
Measure
2.9 - Permitting and Reporting:
The Process and Requirements

2.10 - Federal and State-Owned
MS4s: Program Implementation

Construction Program

3.0 - Construction Program
Overview

Industrial "No Exposure"

4.0 - Conditional No Exposure
Exemption for Industrial Activity
Storm   Water  Phase  II

Proposed  Rule



Post-Construction  Runoff Control

Minimum Control Measure

This fact sheet is basedon the Storm Water Phase II Proposed Rule. Therefore, the information provided herein is subject to
change upon publication of the final Phase II rule in November 1999. A revised series of fact sheets will be provided at that
time. A comprehensive list of the current fact sheets is in the text box at left.

This fact sheet profiles the proposed Post-Construction Runoff Control minimum control measure,
one of six measures that the owner or operator of a Phase II regulated small municipal separate storm
sewer system (MS4) would be required to include in its storm water management program in order to
meet the conditions of its National Pollutant Discharge Elimination System (NPDES) permit. This
fact sheet outlines the Phase II Proposed Rule requirements and offers some general guidance on how
to satisfy them. It is important to keep in mind that the small MS4 owner or operator would have a
great deal of flexibility in choosing exactly how to satisfy the minimum control measure requirements.

Why Is The Control of Post-Construction Runoff Necessary?

   Post-construction storm water management in areas undergoing new development or redevelopment
   is necessary because runoff from these areas has been shown to significantly effect receiving
waterbodies. The Nationwide Urban Runoff Program study (Final Report of the Nationwide Urban
Runoff Program. U.S. EPA, Office of Water,  1983), and more recent studies indicate that prior
planning and design for the minimization of pollutants in post-construction storm water discharges is
the most cost-effective approach to storm water quality management.

There are generally two forms of substantial impacts of post-construction runoff.  The  first is caused
by an increase in the type and quantity of pollutants in storm water runoff.  As runoff flows over areas
altered by development, it picks up harmful sediment and chemicals such as oil and grease, pesticides,
heavy metals, and nutrients (e.g., nitrogen and phosphorus).  These pollutants often become
suspended in runoff and are carried to receiving waters, such as lakes, ponds, and streams. Once
deposited, these pollutants can enter the food chain through small aquatic life, eventually entering the
tissues of fish and humans. The second kind of post-construction runoff impact occurs by increasing
the quantity of water delivered to the waterbody during storms. Increased impervious  surfaces
interrupt the natural cycle of gradual percolation of water through vegetation and soil.  Instead, water
is collected from surfaces such as asphalt and concrete and routed to drainage systems where large
volumes of runoff quickly flow to the nearest receiving water. The effects of this process include
streambank scouring and downstream flooding, which often lead to a loss of aquatic life and damage
to property.

What Is EPA Proposing?

   The Phase II Proposed Rule would require an owner or operator of a regulated small MS4 to
   develop, implement, and enforce a program to reduce pollutants in post-construction runoff to
their MS4 from new development and redevelopment projects that result in the land disturbance of
greater than or equal to 1 acre. The small  MS4 owner or operator would be required to:

  Q    Have a plan to implement structural and/or non-structural best management practices (BMPs)
       and ensure adequate long-term operation and maintenance of such BMPs;

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Fact Sheet 2.7 - Post-Construction Runoff Control Minimum Control Measure
                                                   Page 2
   Q     Ensure that controls are in place that would prevent or
         minimize water quality impacts; and

   Q     Determine the appropriate best management practices
         (BMPs) and measurable goals for this minimum control
         measure.

What Would Be Considered a "Redevelopment"
Project?

    The term "redevelopment" is intended to refer to alterations of
    a property that change the "footprint" of a site or building in
such a way that the disturbance of equal to or greater than 1 acre
of land results. The term is not intended to include such activities
as exterior remodeling. To account for the various types of
redevelopment projects, the proposed rule contains enough
flexibility to allow post-construction controls for redevelopment
to be different than those for new development.

What Are Some Guidelines for Developing and
Implementing This Measure?

    This section includes some  sample non-structural and structural
    BMPs that could be used to satisfy the requirements of the
post-construction runoff control minimum measure. Because the
proposed requirements of this measure are closely tied to the
requirements of the construction site runoff control minimum
measure (see Fact Sheet 2.6), EPA recommends that small MS4
owners or operators develop and implement these two measures
in tandem.  Sample BMPs follow.

Q    Non-Structural BMPs

   Planning and Procedures. Runoff problems can be
    addressed efficiently with sound planning procedures.
    Master Plans, Comprehensive Plans, and zoning ordinances
    can promote improved water quality by guiding the growth of
    a community away from sensitive areas and by restricting
    certain types of growth (industrial, for example) to areas that
    can support it without compromising water quality.

    Site-Based Local  Controls. These controls can include
    buffer strip and riparian zone preservation, minimization of
    disturbance and imperviousness, and maximization of open
    space.

Q    Structural BMPs

    Storage Practices. Storage or detention BMPs control storm
    water by gathering runoff in wet ponds, dry basins, or
    multichamber catch basins and slowly releasing it to
    receiving waters or drainage systems. These practices both
    control storm water volume and settle out particulates for
    pollutant removal.
    Infiltration Practices. Infiltration BMPs are designed to
    facilitate the infiltration of runoff through the soil to ground
    water, and, thereby, result in reduced storm water quantity
    and reduced mobilization of pollutants. Examples include
    infiltration basins/trenches, dry wells, and porous pavement.

   Vegetative Practices.  Vegetative BMPs are landscaping
    features that, with optimal design and good soil conditions,
    enhance pollutant removal, maintain/improve natural site
    hydrology, promote healthier habitats, and increase aesthetic
    appeal.  Examples include grassy swales, filter strips,
    artificial wetlands, and rain gardens.

What Would Be Appropriate Measurable Goals?

     Measurable goals, which would be required for each minimum
     control measure, are meant to help gauge permit compliance
and program effectiveness.  The measurable goals, as well as the
BMPs, would greatly depend on the needs and characteristics of
the owner/operator and the area served by its small MS4. The
measurable goals should be chosen using an integrated approach
that would fully address the requirements and intent of the
minimum control measure.  An integrated approach for this
minimum measure could include the following goals:

Target Date    Activity
1 year	    Strategies developed that include structural
                and/or non-structural BMPs.
2 years	    Strategies codified by use of ordinance or other
                regulatory mechanism.
3 years	    Reduced percent of new impervious surfaces
                associated with new development projects.
4 years	    Improved clarity and reduced sedimentation of
                local waterbodies.
             For Additional Information

   Contact
   es'  U.S. EPA Office of Wastewater Management
          Phone :   202 260-5816
           E-mail:   SW2@epa.gov
           Internet:  www.epa.gov/owm/sw2.htm

   Reference Documents
   ISP  Storm Water Phase II Proposed Rule Fact Sheet
       Series.
           Contact the U.S. EPA Water Resource Center at
           202 260-7786 or at waterpubs@epa.gov
           Internet:  www.epa.gov/owm/sw2.htm

   Vs  Storm Water Phase II Proposed Rule, published on
       Jan. 9, 1998 in the Federal Register (63 FR 1536).
           Internet:  www.epa.gov/owm/sw2.htm

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