(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.
(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.
