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*<u>What is a municipal separate storm sewer system (MS4)?</u> | *<u>What is a municipal separate storm sewer system (MS4)?</u> | ||
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+ | <div title="Only certain MS4s in Minnesota are subject to stormwater regulation under the Clean Water Act and Minnesota Rule 7090. The MPCA regulates the following: | ||
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+ | *An MS4 located fully or partially within an urbanized area as determined by the latest Decennial Census and owned or operated by a publicly owned entity that has the potential resident capacity, bed count occupancy, or average daily user population of 1,000 or more. See [https://stormwater.pca.state.mn.us/index.php?title=Information_about_the_2019_Legislation_and_affected_MS4s changes in regulated areas for cities and townships due to 2019 Legislation] for more information. | ||
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+ | *An MS4 owned or operated by a municipality with a population of 10,000 or more. | ||
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+ | *An MS4 owned or operated by a municipality with a population of at least 5,000 and discharges or has the potential to discharge stormwater to one of the following: | ||
+ | **A water identified as an outstanding resource value water as identified in Minn R. 7050.0180, subparts 3 and 6. | ||
+ | **A water identified as a trout lake or trout stream as identified in Minn. R. 6264.0050, subparts 2 and 4. | ||
+ | **A water listed as impaired under section 303(d) of the Clean Water Act, 33 U.S.C. § 1313. | ||
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+ | Owners or operators of MS4s that meet the above criteria must submit an MS4 General Permit to the MPCA. Under the permit, the owner or operator is required to reduce the amount of sediment and pollution carried from stormwater to surface and ground water to the maximum extent practicable. Additionally, the permit requires the system owner or operator to develop a stormwater pollution prevention program (SWPPP) that incorporates best management practices (BMPs) most appropriate to their MS4. | ||
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+ | Note: The cities of Minneapolis and St. Paul are Large MS4s (population of 250,000 or more) and received reissued individual NPDES/SDS permits on January 21, 2011."> | ||
+ | *<u>Why is a municipality regulated under the MS4 permit?</u> | ||
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*[[What is a municipal separate storm sewer system (MS4)?]] | *[[What is a municipal separate storm sewer system (MS4)?]] |
The municipal separate storm sewer system (MS4) stormwater program is designed to reduce the amount of sediment and pollution that enters surface and ground water from storm sewer systems. Public entities that own or operate an MS4 play a key role in preventing or reducing the negative impacts stormwater runoff has on our valuable water resources.
Proper stormwater runoff management in urbanized areas is especially important for restoring and protecting surface waters. Urbanized areas are more likely to have activities that contribute pollutants to stormwater runoff, like applying anti/deicing mixtures to roads; fueling vehicles; grease, oil, and other spills; landscaping; and using pesticides and fertilizers. Urbanized areas have a large amount of impervious surfaces, or surfaces that rain and snowmelt cannot pass through, such as streets, driveways, rooftops, parking lots and sidewalks. Stormwater runoff from these surfaces travels faster and in higher amounts, damaging rivers, streams, and wetlands; destroying aquatic habitats; increasing the amount of pollutants that enter surface waters; and limiting groundwater recharge.
Visit the MS4 General Permit reissuance page for updates on the new MS4 General Permit.
When seeking to manage a Municipal Storm Sewer System (MS4), an effective Stormwater Pollution Prevention Program (SWPPP) has six different components known as Minimum Control Measures (MCMs). Follow this link to learn more about each MCM along with resources and guidance.
Total Maximum Daily Loads (TMDLs) are EPA approved amounts of pollutant loading that can occur and have a water body meet water quality standards. Follow this link to learn more about them along with guidance and resources.
The U.S. Environmental Protection Agency (EPA) mandates the Minnesota Pollution Control Agency (MPCA) to evaluate MS4 permittees for compliance with the MS4 General Permit. The MPCA does this through compliance audits. To find out more information about the audit process see the pages below: