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Municipal Stormwater Program An Overview wq-sw1-04 • April 2008 Minnesota Pollution Control Agency • 520 Lafayette Rd. N., St. Paul, MN 55155-4194 • www.pca.state.mn.us 651-296-6300 • 800-657-3864 • TTY 651-282-5332 or 800-657-3864 • Available in alternative formats wq-sw1-04 he Municipal Separate Storm Sewer System (MS4) general permit is mandated by the federal regulations under the Clean Water Act and administered by the Minnesota Pollution Control Agency. The MS4 permitting program gives owners or operators of municipal separate storm sewer systems approval to discharge stormwater to lakes, rivers and wetlands in Minnesota. Environmental harm Urban stormwater frequently contains litter, oil, chemicals, toxic metals, bacteria, and excess nutrients, like nitrogen and phosphorous. Polluted stormwater contributes to swimming-beach closings, fish-eating advisories, excess algae growth and poor water clarity in urban water resources, especially lakes. In addition to human effects, poorly managed urban stormwater can drastically alter the natural flow and infiltration of water, scour stream banks and harm or eliminate aquatic organisms and ecosystems. The primary goal of the MS4 general permit is to improve water quality by reducing pollutants in stormwater discharges. Specifically, the program aims to ensure proper management of stormwater discharges into waters of the state. Defining MS4s In general terms, MS4s are publicly owned or operated stormwater infrastructure, used solely for stormwater, and which are not part of a publicly owned wastewater treatment system. Examples of stormwater infrastructure include curbs, ditches, culverts, stormwater ponds and storm sewer pipes. Common owners or operators of MS4s include cities, townships and public institutions. The MS4 general permit focuses on reducing the pollution that enters these public systems and discharges to wetlands, streams and lakes (“waters of the state”). Owners and operators of MS4s which are required to get a permit are created in one of three ways: By federal rule, 40 CFR § 122.34 (a) and (b) (the Clean Water Act), state rule (Minnesota Rules Chapter 7090), or by public petition to the Minnesota Pollution Control Agency. By federal rule, stormwater systems in urban areas are labeled Mandatory MS4s. In addition to these, Minnesota added other stormwater systems (Designated MS4s) to the list. These MS4s are only added if the stormwater system is located in an urban area that meets the criteria established in the State Rule for population and discharge points. The number of MS4s in Minnesota is growing as urban areas expand. As of April 2008, there were 243 MS4s in Minnesota. Public Process After a term of five years, the MS4 general permit is improved and revised, if necessary, and re-issued. Public comment T