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The following guidance, developed by MPCA’s Stormwater Program in conjunction with MPCA’s TMDL Program, discusses recommended procedures for addressing wasteload allocations for current or future municipal stormwater discharges regulated under a National Pollutant Discharge Elimination System (NPDES) permit. The guidance clarifies previous policy for setting wasteload allocations for stormwater and will be modified to address new issues as they arise in TMDLs. The guidance provides clarity about existing stormwater discharges that are covered under a NPDES permit and is specific to municipal stormwater discharges (not industrial or construction).
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==Summary of guidance==
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*The Wasteload Allocation (WLA) must include all drainage from within a regulated municipality or township that discharges from a Municipal Separate Storm Sewer System (MS4) owned or operated by the municipality or township. The WLA may include all drainage from within a regulated municipality or township that is likely to be served by a regulated Municipal Separate Storm Sewer System (MS4) in the future and will be owned or operated by the municipality or township.
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*For regulated counties, watershed districts, and non-traditional MS4s, the WLA should only include the area of the regulated MS4 (i.e. road right-of-ways) and property owned or operated by the regulated entity.
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*Current or future  drainage fromoutside a regulated municipality or township must be included in the Load Allocation (LA).
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*A separate Reserve Capacity cannot be developed for regulated stormwater. Future discharges may be included in the WLA or the Load Allocation (LA).
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*Future discharges from MS4s that are currently permitted can be determined using land use plans or similar documents.
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*MS4s not currently under permit coverage but that will be under NPDES permit coverage, based on one or more criteria described later in this document, may be accounted for in the WLA. These MS4s should receive individual WLAs.
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*Load may be transferred from either the LA or WLA to a WLA. The TMDL should state that the process for transferring load will be consistent with the method used to establish the TMDL.
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*Direct discharges from nonpoint sources to an impaired water cannot be regulated under a NPDES permit. However, for purposes of practicality, loads associated with these discharges may be placed into the WLA if they are not easily quantifiable and constitute a small percentage of the total WLA.
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*The WLA for stormwater may include discharges from municipal, construction, and industrial stormwater if all industrial and construction stormwater discharges occur within the current or future boundaries of a regulated municipality or township.
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==Definition of wasteload allocation==
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The Wasteload Allocation (WLA) is the portion of a receiving water's loading capacity that is allocated to one of its existing or future point sources of pollution. WLAs constitute a type of water quality-based effluent limitation (40 CFR 130.2). NPDES-permitted stormwater discharges must be included in the WLA.
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==Definition of regulated MS4s==
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To understand the basis for making decisions about what should or should not go into the WLA, it is necessary to understand the definition of an MS4.
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*An MS4 is any publicly owned or operated separate storm sewer system. An MS4 is not a municipality, township, county, etc. – it is the conveyance system owned or operated by one of those public entities.
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*Regulated MS4s are those stormwater systems covered under a NPDES permit. MS4s include the following:
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**MS4s owned or operated by municipalities – the permit covers any MS4 within the entire jurisdictional area of a regulated municipality;
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**MS4s owned or operated by townships – the permit covers any MS4 within the entire jurisdictional area of a regulated township;
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**MS4s owned or operated by counties – only MS4s owned or operated by a county within a U.S. Census Bureau Urban Area are covered under permit;
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**MS4s owned or operated by a watershed district – only MS4s owned or operated by a watershed district within a U.S. Census Bureau Urban Area are covered under permit;
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**MS4s owned or operated by MnDOT (Minnesota Department of Transportation) – only MS4s owned or operated by MnDOT within a U.S. Census Bureau Urban Area are covered under permit; and
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**MS4s owned or operated by a nontraditional entity such as a hospital or university – only MS4s owned or operated by a nontraditional entity within a U.S. Census Bureau Urban Area are covered under permit.
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The figure below illustrates the  eight Urban Areas that occur in Minnesota based on the  2010 U.S. Census. They include the Twin Cities, St. Cloud, Duluth, Rochester, Mankato, Fargo-Moorhead, Grand Forks-East Grand Forks, and La Crosse-La Crescent metropolitan areas.
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*It is only the conveyance system owned or operated by the regulated entity that is covered under permit.
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[[file:CensusUA.png|thumb|alt = census urban area|Location of Minnesota's eight urban areas, based on the 2010 U.S. Census.]]

Revision as of 17:10, 14 January 2015

This site is currently undergoing revision. For more information, open this link.
This site is under construction. Anticipated completion date is early January, 2015.

The following guidance, developed by MPCA’s Stormwater Program in conjunction with MPCA’s TMDL Program, discusses recommended procedures for addressing wasteload allocations for current or future municipal stormwater discharges regulated under a National Pollutant Discharge Elimination System (NPDES) permit. The guidance clarifies previous policy for setting wasteload allocations for stormwater and will be modified to address new issues as they arise in TMDLs. The guidance provides clarity about existing stormwater discharges that are covered under a NPDES permit and is specific to municipal stormwater discharges (not industrial or construction).

Summary of guidance

  • The Wasteload Allocation (WLA) must include all drainage from within a regulated municipality or township that discharges from a Municipal Separate Storm Sewer System (MS4) owned or operated by the municipality or township. The WLA may include all drainage from within a regulated municipality or township that is likely to be served by a regulated Municipal Separate Storm Sewer System (MS4) in the future and will be owned or operated by the municipality or township.
  • For regulated counties, watershed districts, and non-traditional MS4s, the WLA should only include the area of the regulated MS4 (i.e. road right-of-ways) and property owned or operated by the regulated entity.
  • Current or future drainage fromoutside a regulated municipality or township must be included in the Load Allocation (LA).
  • A separate Reserve Capacity cannot be developed for regulated stormwater. Future discharges may be included in the WLA or the Load Allocation (LA).
  • Future discharges from MS4s that are currently permitted can be determined using land use plans or similar documents.
  • MS4s not currently under permit coverage but that will be under NPDES permit coverage, based on one or more criteria described later in this document, may be accounted for in the WLA. These MS4s should receive individual WLAs.
  • Load may be transferred from either the LA or WLA to a WLA. The TMDL should state that the process for transferring load will be consistent with the method used to establish the TMDL.
  • Direct discharges from nonpoint sources to an impaired water cannot be regulated under a NPDES permit. However, for purposes of practicality, loads associated with these discharges may be placed into the WLA if they are not easily quantifiable and constitute a small percentage of the total WLA.
  • The WLA for stormwater may include discharges from municipal, construction, and industrial stormwater if all industrial and construction stormwater discharges occur within the current or future boundaries of a regulated municipality or township.

Definition of wasteload allocation

The Wasteload Allocation (WLA) is the portion of a receiving water's loading capacity that is allocated to one of its existing or future point sources of pollution. WLAs constitute a type of water quality-based effluent limitation (40 CFR 130.2). NPDES-permitted stormwater discharges must be included in the WLA.

Definition of regulated MS4s

To understand the basis for making decisions about what should or should not go into the WLA, it is necessary to understand the definition of an MS4.

  • An MS4 is any publicly owned or operated separate storm sewer system. An MS4 is not a municipality, township, county, etc. – it is the conveyance system owned or operated by one of those public entities.
  • Regulated MS4s are those stormwater systems covered under a NPDES permit. MS4s include the following:
    • MS4s owned or operated by municipalities – the permit covers any MS4 within the entire jurisdictional area of a regulated municipality;
    • MS4s owned or operated by townships – the permit covers any MS4 within the entire jurisdictional area of a regulated township;
    • MS4s owned or operated by counties – only MS4s owned or operated by a county within a U.S. Census Bureau Urban Area are covered under permit;
    • MS4s owned or operated by a watershed district – only MS4s owned or operated by a watershed district within a U.S. Census Bureau Urban Area are covered under permit;
    • MS4s owned or operated by MnDOT (Minnesota Department of Transportation) – only MS4s owned or operated by MnDOT within a U.S. Census Bureau Urban Area are covered under permit; and
    • MS4s owned or operated by a nontraditional entity such as a hospital or university – only MS4s owned or operated by a nontraditional entity within a U.S. Census Bureau Urban Area are covered under permit.

The figure below illustrates the eight Urban Areas that occur in Minnesota based on the 2010 U.S. Census. They include the Twin Cities, St. Cloud, Duluth, Rochester, Mankato, Fargo-Moorhead, Grand Forks-East Grand Forks, and La Crosse-La Crescent metropolitan areas.

  • It is only the conveyance system owned or operated by the regulated entity that is covered under permit.
Location of Minnesota's eight urban areas, based on the 2010 U.S. Census.