Wisconsin Administrative Code › Department of Natural Resources › NR 200-299 - Environmental Protection - Wisconsin Pollutant Discharge Elimination System › Chapter NR 212 - Waste Load Allocated Water Quality Related Effluent Limitations › Subchapter III - Development of Total Maximum Daily Loads and Effluent Limitations Developed Through Wasteload Allocations › Section NR 212.73 - TMDL development requirements for impaired waters

Current through June 24, 2024
(1) PURPOSE. This
				  section establishes the procedure, methodologies, and requirements to be used
				  for developing TMDLs.
(2)
				  PRIORITIZATION. The department shall create and maintain an impaired waters
				  list of waters that fail to meet water quality standards and, therefore,
				  require the development of TMDLs or alternative remediation plans. The impaired
				  waters list shall include a priority ranking for the development of a TMDL for
				  all listed waters. The priority ranking shall consider the severity of the
				  pollution, the uses to be made of such waters, and whether implementing
				  existing TBELs and WQBELs in permits are sufficient to achieve water quality
				  standards. By April 1 of each even-numbered year, the Department shall submit
				  to the EPA a prioritized ranking of waters on the impaired waters list targeted
				  for TMDL development for a two-year period. Impaired waters addressed by
				  alternative remediation plans may be assigned a low priority for TMDL
				  development on the impaired waters list.
Note:
The impaired waters listing and priority
					 setting process is specified in the Wisconsin Consolidated Assessment and
					 Listing Methodology (WisCALM).
Note:
Examples of remediation plans include,
					 but are not limited to, lake protection and restoration plans, remedial action
					 plans, environmental accountability projects, area-wide water quality
					 management plans, adaptive management plans, and nine key element watershed
					 plans.
(3) TMDL DEVELOPMENT.
(a) The department shall establish TMDLs for
				  impaired waters in accordance with the prioritization in sub. (1). TMDLs shall
				  be established at levels necessary to attain and maintain applicable numeric
				  and narrative water quality standards with seasonal variations and a margin of
				  safety that takes into account any lack of knowledge concerning the
				  relationship between effluent limitations and water quality. TMDLs shall take
				  into account critical conditions for stream flow, loading, and water quality
				  parameters.
(b) TMDLs shall be
				  established to ensure attainment of all designated uses and applicable numeric
				  and narrative water quality standards for the pollutant of concern including
				  applicable numeric and narrative criteria under chs.
				  NR 102 and 105.
(c) TMDLs may be established using a
				  pollutant-by-pollutant or biomonitoring approach. In many cases both techniques
				  may be needed. Site specific information should be used whenever
				  possible.
(d) TMDLs shall include
				  wasteload allocations for point sources and load allocations for nonpoint
				  sources such that the sum of the allocations is not greater than the loading
				  capacity of the water for the pollutants addressed by the TMDL, minus the sum
				  of natural background loads, the reserve capacity and, if specified, an
				  explicit margin of safety. Allocations shall meet the following requirements:
1. Allocations shall be distributed to
				  sources using a baseline loading condition that is defined in the
				  TMDL.
2. If allocations in the TMDL
				  are expressed as a concentration, the TMDL shall also indicate the flows,
				  including effluent flows, assumed in the analyses.
3. If multiple EPA-approved TMDLs are
				  prepared for impaired waters, and the TMDLs include allocations for the same
				  pollutant for one or more of the same sources, then the applicable allocations
				  that are protective of both immediate and downstream segments shall be used for
				  TMDL implementation, including permitting.
4. Pollutant degradation and transport may be
				  considered when developing allocations.
5. Natural background loads may be accounted
				  for in a TMDL through an allocation to a single category or through individual
				  allocations to applicable sources of natural background loads.
6. Nonpoint sources may be accounted for in a
				  TMDL through an allocation to a single category or through individual load
				  allocations to various nonpoint sources.
7. Point source dischargers covered through
				  individual permits shall be assigned individual waste load allocations. Point
				  source dischargers covered through general permits may be accounted for through
				  an allocation to a single category or through individual wasteload
				  allocations.
(e) TMDLs
				  shall include a margin of safety sufficient to account for technical
				  uncertainties in establishing the TMDL and shall describe the manner in which
				  the margin of safety is determined and incorporated into the TMDL. The margin
				  of safety may be provided explicitly by leaving a portion of the loading
				  capacity unallocated, implicitly by using conservative modeling assumptions to
				  establish wasteload allocations and load allocations, or a combination thereof.
				  If a portion of the loading capacity is left unallocated to provide a margin of
				  safety, the amount left unallocated shall be documented. If conservative
				  modeling assumptions are relied on to provide a margin of safety, the specific
				  assumptions providing the margin of safety shall be described.
(f) A portion of the TMDL may be allocated to
				  a reserve capacity to account for new or increased discharges, or other sources
				  not allocated in the TMDL. When such reserve allocations are not included in a
				  TMDL, any increased loadings of the pollutant for which the TMDL was developed
				  that are due to a new or expanded discharge may not be allowed unless the TMDL
				  is revised to include an allocation for the new or expanded discharge or the
				  new or expanded discharge is offset by a reduction of the pollutant in the
				  watershed covered by the TMDL.