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; ------- 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 ------- |