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==Appendix A - Examples== | ==Appendix A - Examples== | ||
− | + | Under review. | |
+ | |||
+ | ==Appendix B - New candidates for NPDES coverage.== | ||
+ | Under review. | ||
+ | |||
+ | ==Appendix C - Met Council Land Use Classifications== | ||
+ | The following land uses are discussed in Met Council’s various planning documents. The list contains a mixture of land use. For each item in the list, a short statement discussing the relationship with the WLA is included in italics. | ||
+ | *01 - Single Family Residential: Includes all individual, free standing single family housing (including manufactured housing). Within the MUSA (metropolitan urban service area) and in residential developments outside the MUSA, the lot lines visible on the photos were used for determining residential land use boundaries. Where residential developments were visibly not complete, the undeveloped area was classified as vacant. For the scattered, rural residential areas outside the MUSA, only the portion of lots used for residences was assigned to the residential category. ''MPCA comment: This includes a wide range of land uses, some of which may be agricultural. Within the MUSA, it is generally appropriate to place this in the WLA.'' | ||
+ | *02 - Multi-Family Residential: Includes all multiple dwelling units such as duplexes, bungalows, twin homes, townhouses, quad homes and apartment complexes. Also, buildings that are primarily apartments that have some group dining facilities are included (however, not those buildings that fit the census definition of 'Group Quarters', such as, dormitories, nursing homes or medical care facilities). ''MPCA comment: It will generally be appropriate to place this in the WLA, particularly within the MUSA.'' | ||
+ | *03 – Commercial: Includes all retail sales, services, hotels and motels, health care facilities (e.g. medical and dental clinics and offices and medical laboratories, but not hospitals and nursing homes) and recreational services that are predominantly privately owned and operated for profit (e.g. theaters, bowling alleys, equestrian ranches) except golf courses. Hospitals and nursing homes are included in the 'Public & Semi-Public' category and golf courses are in the 'Parks & Recreation Areas' class. For large shopping centers, only actual developed areas are shown. This is done so that over the years new development can be shown (e.g. restaurants or gas stations on perimeter roads). ''MPCA comment: Within the MUSA, it is generally appropriate to place this in the WLA.'' | ||
+ | *04 – Industrial: Includes the Federal Standard Industrial Classification (SIC) codes 14 through 50. This includes manufacturing, transportation, construction, communications, utilities, and wholesale trade. Also included in the 'Industrial' category are some horticultural specialty land uses (e.g. large greenhouses that do not sell to the public). As of 1997, gravel pits and quarrying have been placed in a new category called 'Extractive' and all publicly owned areas that are predominantly of industrial nature have been placed in a new category called 'Public Industrial.' ''MPCA comment: Within the MUSA, it is generally appropriate to place this in the WLA.'' | ||
+ | *05 - Public Semi-Public: Includes the land under and adjacent to schools (public and private), hospitals, churches, cemeteries, ice arenas and all facilities of local, state and federal governments, including convalescent homes, mental institutions and penal facilities maintained by any level of government. All lands within the boundaries of these institutions and facilities are included in this category. However, in certain instances unused lands were included in the 'Public & Semi-Public Vacant' category (e.g. the University of Minnesota's property in Rosemount, or part of the land adjacent to the Minnesota Veterans Home in Hastings). ''MPCA comment: Within the MUSA, it is generally appropriate to place this in the WLA.'' | ||
+ | *06 – Airports: All types of airports. ''MPCA comment: Within the MUSA, it is generally appropriate to place this in the WLA.'' | ||
+ | *07 - Parks & Recreation Areas: Includes all parks (city, regional and state), wildlife refuges, playgrounds, zoos, gun clubs, golf courses and similar areas (this includes DNR wildlife management areas and scientific and natural areas). Parks are delineated using their actual boundaries taken directly off comprehensive plans, park maps or county parcel data. ''MPCA comment: Within the MUSA, it is generally appropriate to place this in the WLA.'' | ||
+ | *08 - Vacant/Agricultural: Includes land identifiable from aerial photos as open and in agriculture uses, other uses where no buildings are present or unused land. Please note that indoor horticultural specialty land uses (the growing of nursery stock, flowers, seeds, sod and food crops in large greenhouses that do not sell to the public; and large concentrations of agricultural buildings (e.g., barns, sheds and silos)) are included in the 'Industrial' category where they can be delineated. Where residential uses are on larger lots, the residential land use category may include only the house and mowed portion of the parcel, with the rest being placed in this Vacant and Agricultural category. ''MPCA comment: This contains a mixture of land uses. Agricultural areas should be placed into the LA. Vacant areas should be placed into the appropriate category based on the adjacent land use.'' | ||
+ | *09 - Major Four Lane Highways: Includes only the major interstate freeways and 4 lane divided highways with rights-of-way of 200 feet or greater. Also included in 1997 are all 4-lane roads with a Metropolitan Council functional class designation of 'Principal Arterial.' ''MPCA comment: These will generally be owned and operated by MnDOT. Regulated portions (within urban areas) should be included in the WLA.'' | ||
+ | *10 - Open Water Bodies: Includes lakes of 5 or more acres and rivers 200 feet or wider. ''MPCA comment: Water bodies are typically excluded from the WLA and LA.'' | ||
+ | *11 – Farmsteads: Includes only that portion of land that encompasses the buildings on the farmstead. ''MPCA comment: Place into the LA.'' | ||
+ | *12 – Extractive: New category in 1997. Includes all gravel pits and quarries. ''MPCA comment: Placed into appropriate category based on surrounding land use.'' | ||
+ | *41 - Industrial Parks not Developed: Parcels of land in a designated (named) industrial park but not developed. ''MPCA comment: Placed into appropriate category based on surrounding land use.'' | ||
+ | *51 - Public & Semi-Public Vacant: A government or university owned parcel of land that is undeveloped (e.g. part of arsenal site in Arden Hills or the University property in Rosemount). ''MPCA comment: If it is not a regulated MS4, place into the appropriate category based on surrounding land use.'' | ||
+ | *54 - Public Industrial: New category in 1997. Includes all publicly owned areas that are predominantly of an industrial nature (e.g. waste water treatment plants, city bus garages, and Dept. of Transportation sand and salt stockpiling areas). In the past, some of these have been coded as industrial and others as public. ''MPCA comment: If it is not a regulated MS4, place into the appropriate category based on surrounding land use.'' | ||
+ | *SINGLE FAMILY RESIDENTIAL: Land used exclusively for residential purposes and containing a single dwelling unit. Includes the following four codes: | ||
+ | **111: FARMSTEAD: Land that encompasses the single family residential dwelling and associated buildings of a farm. Associated buildings of a farm may include buildings used for animal husbandry (barns, chicken coops, grain solos, etc.) along with accessory uses, provided that such accessory uses are incidental to the agricultural activities. ''MPCA comment: Place into the LA.'' | ||
+ | **112 - SEASONAL/VACATION: Land meeting the general definition of single-family residential containing a dwelling unit occupied seasonally or used as vacation property. ''MPCA comment: Generally will be in the LA.'' | ||
+ | **113 - SINGLE FAMILY DETACHED: Land meeting the general definition of single-family residential and detached from any other residential dwelling unit (i.e., with open space on all four sides, includes detached town homes). ''MPCA comment: Generally will be in the WLA.'' | ||
+ | **116 - MANUFACTURED HOUSING PARK: Land meeting the general definition of Single-Family, Detached dwelling and designated for the placement of multiple manufactured housing structures. Note: this classification IS NOT used for an individual manufactured home. ''MPCA comment: Generally will be in the WLA.'' | ||
+ | *MULTIFAMILY RESIDENTIAL: Land used exclusively for residential multiple-family dwellings containing a building or multiple buildings. Includes the following two codes: |
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).
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.
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.
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.
Minnesota’s MS4 General Permit defines MS4 as a “conveyance or system of conveyances (including roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, man-made channels, or storm drains)”. This term may lead to confusion, however, since some of these features may also be classified as waters of the state and therefore protected for compliance with water quality standards. Minnesota Rules 7050.0130 Subp. 2 states “… disposal systems or treatment works operated under permit or certificate of compliance of the agency are not "waters of the state." Therefore, an MS4 cannot also be a water of the state. For example, some ditches are assessed as 2B waters and therefore cannot be MS4s. Any waterbody that could be considered a water of the state should be treated as such and therefore be included in the LA unless the MPCA’s stormwater program has made a determination that they are MS4s.
The issuance of a NPDES permit provides reasonable assurance that the WLAs contained in a TMDL will be achieved. This is because 40 C.F.R. 122.44(d)(1)(vii)(B) requires that effluent limits in permits be consistent with "the assumptions and requirements of any available waste load allocation" in an approved TMDL. The MPCA’s Phase 1 permit requires Minneapolis and St. Paul to estimate pollutant loadings and compare those to any applicable WLA. The Phase 2 General Permit requires permittees to demonstrate annual progress toward meeting any applicable WLA to the Maximum Extent Practicable.
MS4 permits only cover water in a publicly-owned or -operated conveyance. Discharges to conveyances are not covered under permit. However, the conveyance must be in compliance with requirements of the permit, which means discharges to a public conveyance must also be managed. Municipalities and townships have necessary regulatory tools to control discharges to their system, although these authorities vary widely from location to location. Factors influencing local regulatory authority include local zoning ordinances, county regulations, and ditch law. Other MS4 permittees typically do not have these regulatory authorities.
MPCA policy on setting WLAsprovides a general framework for addressing WLAs, but experience with TMDLs indicated the policy needed updating. The following guidance provides clarification for the policy. The guidance will need to be updated as new TMDLs are developed and new issues arise.
When assessing which pollutant loads should be placed into the WLA, it is necessary to clearly define what is covered under a NPDES permit. Minnesota’s Phase 2 General Permit states “Only your [the permittee’s] system and the portions of the storm sewer system that are under your operational control are authorized by your permit”([1]). MPCA interprets this to mean an MS4 is responsible for ensuring its discharge is in compliance with water quality based effluent limits (WQBELs), since the discharge is within the publicly owned or operated conveyance system. The permittee must take appropriate measures to bring its MS4 into compliance. All drainage discharging from a regulated MS4 or to a regulated MS4 from property owned or operated by the regulated entity are put into the WLA. Other drainage to a regulated MS4 are also put into the WLA when the permittee has regulatory authority to control the discharges.
TMDLs may narrowly define the sources that are part of the WLA. For example, individual pipes can receive a WLA. This typically will not be the case because there is rarely adequate information to assign WLAs this narrowly. WLAs, however, should be defined as narrowly as data allow. The table below summarizes the above discussion for the general case where contributing sources are not narrowly defined. For a list of MS4s covered by permit, see [2].
The table reveals several complexities. These are discussed below. The flowchart in Figure 1 illustrates a decision process. Examples are provided in Appendix A.
Stormwater discharges (pollutant loads) that typically go to the LA can be included in the WLA if the discharge will eventually be regulated under a NPDES permit. Accounting for future growth in this manner potentially provides incentives to MS4s to implement Low Impact Design (LID) Best Management Practices (BMPs) as development occurs. Incorporating future loads into the WLA also reduces the likelihood that pollutant load will have to be transferred from the Load Allocation (LA) to the WLA which can be problematic if the TMDL report does not clearly establish the procedure for LA to WLA transfers. NOTE: Per EPA’s recent memorandum discussing WLAs for regulated stormwater, LA to WLA transfers are now acceptable without having to re-notice the TMDL, provided the TMDL report explains how the transfer will occur.
MPCA does not advocate individual terms for Reserve Capacity. Reserve Capacity should be built into the WLA or LA. Generally, the WLA will be a lumped total that may include future loads. However, the TMDL can break the WLA down into current and future loads for existing permitted entities. This is not recommended because it makes accounting of loads difficult.
This guidance on future loads applies to nonpoint discharges that currently do not end up in a regulated conveyance system. There are six cases where loads normally put into the LA could be put into the WLA (see below). Note that in all cases, the TMDL report must either assign a WLA to all entities that will come under permit coverage or describe how load transfers will occur once growth occurs. For example, a regulated municipality that will annex a non-regulated township may be given additional WLA to account for growth. If the municipality includes a state highway and a state college, the highway and college should either be given WLAs or the TMDL must describe the mechanism by which WLA will be transferred from the municipality to the other MS4s (see the section on Transfer of Loads).
WLAs assigned for situations 3 through 5 should be individual. WLAs for situation 6 must be individual. Assigning loads for these situations represents an over-allocation based on current land use. The MS4s essentially grow into the allocation. For situations where discharges to impaired waters trigger designation for permit coverage, MPCA’s stormwater program will not designate new MS4s unless they are given a WLA in a U.S. EPA-approved TMDL.
Appendix B contains a list of MS4s that meet designation criteria but have not yet been designated for permit coverage and a list of MS4s that are likely to become mandatory MS4s as a result of a change in an Urban Area. Appendix B is based on 2010 census data.
A memo by the U.S. EPA, dated November 26, 2014, indicates that transfers from the LA to the WLA are acceptable ([3]). This represents a change in U.S. EPA guidance. When LA to WLA transfers are allowed, there is no need to identify future growth areas and account for them in the TMDL. LA to WLA transfers are appropriate for addressing any future growth situation. However, the TMDL report must clearly define the process of such a transfer.
Both LA to WLA and WLA to WLA transfers are acceptable. In no case can the overall TMDL change unless the TMDL is resubmitted to the U.S. EPA.
We strongly recommend all TMDL reports describe a process for transferring either LA or WLA to WLA regardless of the likelihood that such transfers will occur. Example language is provided below. Note item 5, which also addresses future point sources that are not MS4s but discharge stormwater.
Future transfer of watershed runoff loads in this TMDL may be necessary if any of the following scenarios occur within the project watershed boundaries:
Load transfers will be based on methods consistent with those used in setting the allocations in this TMDL [Specify method, if needed, e.g., “Loads will be transferred on a simple land-area basis.”]. In cases where WLA is transferred from or to a regulated MS4, the permittees will be notified of the transfer and have an opportunity to comment.
The last paragraph in this language indicates the method(s) of transfer will be consistent with the method(s) used to establish the allocations in the TMDL. It is preferred that this methodology be included in the above language. For example, the paragraph may state the following:
Load transfers will be based on the method used in setting allocations in the TMDL. Load transfers will therefore be based on the land area requiring WLA and an assumption that loading rates are equivalent for all land uses in the watershed. For example, conversion of 10 percent of the watershed from LA to WLA will result in a 10 percent decrease in the LA and a 10 percent increase in the WLA. In cases where WLA is transferred from or to a regulated MS4, the permittee(s) will be notified of the transfer.
When feasible, it is best to accommodate future loads in the WLA rather than transfer load from the LA. Having growth accounted for in the WLA does not require re-visiting a TMDL every time growth occurs. Placing future loads into the WLA also may provide a better estimate of ultimate loading for an MS4, which in turn may allow permittees to better plan for future loads and future growth.
When determining WLAs using the above guidance, TMDL authors should use the best available data and professional judgment in making determinations about what goes into a WLA. When appropriate, TMDL authors should consult with Stormwater program staff to ensure consistency across all TMDLs. Some factors that may influence the amount of rigor involved in determining the WLA include the following.
In general, we want to avoid a situation where there is a gross over- or under-allocation. An under-allocation occurs when insufficient load is included to accommodate future growth. This forces a permittee to reduce loading from the MS4 within its’ existing area and limits flexibility in choosing BMPs. An over-allocation occurs when too much load is included in the WLA. In this situation, permittees can easily demonstrate they meet their WLA, which results in the permittee not having to implement any BMPs even though their current discharge may contribute to a water quality violation.
Case studies can be found at MPCA’s stormwater webpage ([4]).
Permittees are required to include compliance schedules in their permits when a TMDL WLA is not being achieved at the time of permit application. The TMDL may define the time frame for achieving the TMDL, considering projections of future loads. However, permittees determine a target date they believe each applicable WLA can reasonably be acheived. This date is not enforceable through the MS4 permit.
It is typically not practical to base future loads on knowledge of where stormwater runoff flows. Future loads should therefore be estimated using land use information. In general, areas projected to be urbanized (medium and high density residential, commercial, industrial) can be placed into the WLA because they will likely be served by a regulated MS4. Other land uses, such as agriculture, can be placed into the WLA if there is adequate information to indicate these discharges will be to a regulated MS4 owned or operated by a municipality or township. Some land uses are difficult to assign to the WLA or LA. Appendix C provides a guide for determining how to assign loads based on projected land use.
Conveyance - a system designed for transporting stormwater runoff and owned or operated by a state, city, town, borough, county, parish, district, association, or other public body (created by or pursuant to state law) having jurisdiction over disposal of sewage, industrial wastes, or stormwater. Often referred to as an MS4.
Development Plan - a comprehensive plan that guides future land use.
'Metropolitan Urban Service Area (MUSA) - the area in the seven counties in which the Metropolitan Council ensures that regional services and facilities, such as sewers and major highways, are provided or planned. Currently there is an approved 2020 MUSA line.
MS4 (Municipal Separate Storm Sewer System) - a conveyance or system of conveyances (including roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, man-made channels, or storm drains):
Regulated Stormwater – stormwater discharges covered under a National Pollutant Discharge Elimination System (NPDES) permit.
Urban Area (or Urban Cluster) – a core census block groups or blocks that have a population density of at least 1,000 people per square mile and surrounding census blocks that have an overall density of at least 500 people per square mile.
Under review.
Under review.
The following land uses are discussed in Met Council’s various planning documents. The list contains a mixture of land use. For each item in the list, a short statement discussing the relationship with the WLA is included in italics.