Section 212.73. TMDL development requirements for impaired waters.

 

(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.

(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.

(4)   Monitoring data. Monitoring data shall be collected to support the development of the TMDL and track implementation of a TMDL. Monitoring data shall be used for all of the following:

(a) To demonstrate progress towards achieving water quality standards such as quantifying pollutant reductions made through implementation of the TMDL and evaluating the effectiveness of controls being used to implement the TMDL.

(b) To validate the assumptions and scientific analysis used to establish the TMDL or revise the TMDL, if necessary.

(5)   Reasonable assurance. A TMDL, implementation plan for a TMDL, or remediation plan shall provide reasonable assurances that water quality standards will be attained within a reasonable timeframe. Determining the reasonable period of time in which water quality standards will be met is a case-specific determination considering a number of factors including, but not limited to: receiving water characteristics including persistence, behavior, and ubiquity of pollutants of concern; the types of remedial activities necessary; and available regulatory and non-regulatory controls.

History: CR 15-085 : cr. Register August 2016 No. 728 , eff. 9-1-16.

Note

The impaired waters listing and priority setting process is specified in the Wisconsin Consolidated Assessment and Listing Methodology (WisCALM). Microsoft Windows NT 6.1.7601 Service Pack 1 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. Microsoft Windows NT 6.1.7601 Service Pack 1