Stormwater Management

Unit 3

Stormwater runoff is precipitation that has not been absorbed by the ground; rather it “runs off” over the surface of the land. Runoff can have a large impact on both the land and the water body that it drains into. For example, uncontrolled stormwater runoff can wash away large amounts of exposed dirt from construction sites.

In addition, stormwater runoff can pick up pollutants such as petroleum products, litter, pet wastes, and residues of chemicals from industrial activities. All of these pollutants are carried with the runoff into surface waters where they can adversely affect water quality. Stormwater can severely degrade the water bodies it drains to, accelerate erosion, increase the volume and frequency of flooding, and destroy plants, animal life, and habitat.

Pollutants carried by stormwater increase levels of nitrogen, phosphorous, suspended solids, pathogens, biological oxygen demand, and chemical oxygen demand in the receiving water body. The result is that nearshore areas are less able to support wildlife like young fish. Drinking water intakes may be placed at risk, or the cost of potable water can increase as additional water treatment is needed. Also, using the water for human recreation becomes less desirable.

The volume of stormwater runoff increases as natural forests and fields are replaced with hard surfaces such as buildings, parking lots, driveways, and roads. Without any plants to disrupt the flow and with the installation of conveyances like catch basins, ditches and storm sewers, stormwater moves across the land more quickly than it did under predevelopment conditions.

Best Management Practices and Legal Setting

This Unit includes two sections of best management practices, an overview of the legal setting, and a unit review. First, the Source Control section outlines non-structural best management practices, focusing on keeping stormwater from coming into contact with pollutants. Second, the Stormwater Treatment section provides BMPs — usually involving building structures or installing devices — to treat or manage runoff. The following list provides an outline of best management practices that you will see in each section.

Section 1: Source Control

  • Practice low impact development
  • Plant and maintain vegetated areas
  • Minimize impervious areas
  • Capture and reuse roof water
  • Minimize pollution in runoff
  • Control sediment from construction sites
  • Stencil storm drains

Section 2: Stormwater Treatment

  • Use site analysis to inform BMP selection
  • Use structural controls as necessary

Unit Review

Legal Setting

Before reviewing the best management practices, please take a few moments to review the legal setting for stormwater management. This overview of federal laws and regulations provides you with a basis of understanding. However, it is a starting point and not a complete reference; please consult your state officials for complete requirements. Also, see: State Laws page for your state.

National Pollutant Discharge Elimination System (NPDES) Regulations

In 1987 the Clean Water Act was amended to include requirements for controlling stormwater discharges at certain industrial and construction sites (Section 402, National Pollutant Discharge Elimination System). Under the stormwater regulations, businesses are required to obtain a permit and develop a Stormwater Pollution Prevention Plan (SWP3 or SWPPP). The permit is called a National Pollution Discharge Elimination System (NPDES) permit and is typically issued by the state. For more information see the State Laws page for your state, the NPDES General Permit Inventory (EPA, for latest information on NPDES general permits and expiration dates), and the National Pollutant Discharge Elimination System (EPA, for general information).

Municipalities, townships, and counties also have authority to regulate stormwater and land development through local ordinances. Contact your local Soil and Water Conservation District, or Drainage Authority (i.e., City Engineer), for information on local requirements.

Federal Coastal Nonpoint Source Pollution Control Program

The Coastal Nonpoint Source Pollution Control Program (Section 6217 of the Coastal Zone Act Reauthorization Amendments of 1990) addresses nonpoint pollution problems in coastal waters. States with approved Coastal Zone Management Programs are required to develop plans to reduce pollution from stormwater runoff from a variety of sources, including marinas. This program implements nonpoint source pollution controls, known as management measures that conform to those described in “Guidance Specifying Management Measures for Sources of Nonpoint Pollution in Coastal Waters.” This program is administered jointly between the U.S. Environmental Protection Agency and the National Oceanic and Atmospheric Administration (NOAA). For more information, see: Coastal Nonpoint Source Pollution Control Program (EPA).

Stormwater Permits

During construction, use a storm drain filter to trap pollutants carried to the drain inlet by runoff. This option is not practical for long term use due to maintenance issues. Photo credit: Elaine Isely

Federal regulation (Title 40, CFR, Section 122.26) requires that a regulated facility apply for industrial stormwater permit coverage if stormwater runoff exposed to industrial materials and/or industrial activities discharges to surface waters of the state or into a separate storm sewer system. A stormwater permit may not be required if stormwater does not discharge from the facility site or is discharged into a sewer system that leads to a wastewater treatment plant.

Determining if a Facility is Required to Obtain Permit Coverage:

  1. Is the primary Standard Industrial Classification (SIC) code Federally regulated?
  2. Where does the stormwater go?
  3. Are industrial materials or activities exposed to stormwater runoff?

The federally regulated SIC code list can be viewed at: Standard Industrial Classification Search (OSHA).

Marinas and boatyards requiring NPDES Stormwater Multi-Sector General Permit (MSGP)
or an individual permit are categorized as:

  • SIC codes 3731 and 3732 – Ship and boat building and repair facilities
  • SIC code 4412 – 4499 (Marinas 4493) – Water transportation facilities

Coverage is required for facilities with vessel maintenance shops (e.g. mechanical repairs, painting, fueling, and lubrication) or equipment-cleaning operations.

A stormwater permit is also required for construction activity disturbing one or more acres of land. The construction site permit addresses erosion control and stormwater management. Consult your state for required permits.

For specific stormwater requirements, see the State Laws page for your state.

Stormwater Pollution Prevention Plans

In addition to obtaining a permit for either industrial or construction activities, the stormwater regulations require that businesses develop a stormwater pollution prevention plan (SWPPP or SWP3). In the plan, you must identify potential activities at your business that may contaminate stormwater. In addition, the plan must outline the practices that you will use to help prevent stormwater from becoming contaminated and running off into surface waters.

Typical Contents of a Stormwater Pollution Prevention Plan:

  • Pollution prevention team
  • Description of potential pollutant sources
  • Site map indicating drainage, maintenance/cleaning, and material storage and loading/unloadings areas
  • Inventory of materials exposed to precipitation
  • List of significant spills and leaks that occurred in the 3 years prior to the effective date of the permit
  • Sampling data describing pollutants in stormwater discharges from the facility
  • Summary of potential pollutant sources and identification of associated risks
  • Description of stormwater management controls addressing:
    • Good housekeeping
    • Preventative maintenance
    • Spill prevention and response procedures
    • Inspections
  • Employee training
  • Record keeping and internal reporting procedures
  • Testing and evaluation for non-stormwater discharges
  • Sediment and erosion control
  • A comprehensive site compliance evaluation
  • Enclosure or covering of salt storage facilities
  • Special requirements for stormwater discharges associated with industrial activity from facilities subject to SARA Title III, Section 313 requirements

Even when your state does not require a SWPPP, to achieve Clean Marina certification you should produce a stormwater information map (SIM). A stormwater information map identifies many of the same issues addressed in a SWPPP and will provide important information that may help to improve the quality of surface waters by reducing the amount of pollutants contained in stormwater runoff. For an example of SIM requirements, see: Stormwater Information Map (Wisconsin Clean Marina Program).

See Resources and Tools: Plans for templates and guidance for creating a SWPPP.

Next: Section 1: Source Control