Current through August 26, 2024
(1) BASIS
FOR LIMITATIONS.
(a) The department shall
calculate potential water quality based effluent limitations for point source
dischargers of phosphorus using the procedures in this section.
(b) Water quality based effluent limitations
for phosphorus shall be calculated based on the applicable phosphorus criteria
in s. NR 102.06 at the point of discharge, except the department may calculate
the limitation to protect downstream waters.
(2) DISCHARGES TO STREAMS AND
RIVERS.
(a)
Limitation calculation. For discharges of phosphorus to
flowing streams and rivers, the water quality based effluent limitation shall
be calculated using the following conservation of mass equation:
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Where:
Limitation = Water quality based effluent limitation (in
units of mass per unit of volume),
WQC = The water quality criterion concentration (in units
of mass per unit volume) from s. NR 102.06,
Qs = Receiving water design flow (in units of volume per
unit time) as specified in par. (b),
Qe = Effluent flow (in units of volume per unit time) as
specified in par. (c),
f = Fraction of the effluent flow that is withdrawn from
the receiving water, and
Cs = Upstream concentration (in units of mass per unit
volume) as specified in par. (d).
(b)
Receiving water design flow
(Qs). Based on the availability of information and the professional
judgment of the department, the value of Qs to be used in calculating the
effluent limitation for discharges to flowing waters shall be determined using
one of the following:
1. The average minimum
7-day flow which occurs once every 2 years (7-day Q2)
based on information derived by the U. S. geological survey or other department
approved information source, using data from a representative gauging station
with a period of record of at least 10 years.
2. If provided by the permittee and approved
by the department, the average low 30-day flow which occurs once every 3 years
(30-day Q3) based on information derived by the U. S.
geological survey or other department approved information source, using data
from a representative gauging station with a period of record of at least 10
years.
3. Other flow deemed more
representative of flow conditions and approved by the
department.
(c)
Effluent flows (Qe).
1. For
dischargers subject to ch. NR 210 and which discharge for 24 hours per day on a
year-round basis, Qe shall equal the maximum effluent flow, expressed as a
daily average, that is anticipated to occur for 12 continuous months during the
design life of the treatment facility unless it is demonstrated to the
department that this design flow rate is not representative of projected flows
at the facility.
2. For other
dischargers not subject to ch. NR 210, Qe shall equal, based on the best
professional judgment of the department, one of the following:
a. The maximum effluent flow, expressed as a
365 day rolling average of daily discharges that has occurred for 12 continuous
months and represents normal operations.
b. The maximum effluent flow, expressed as a
30 day rolling average, which has occurred for 30 continuous days and
represents normal operations.
3. For seasonal discharges, discharges
proportional to stream flow, or other non-continuous discharge situations, Qe
shall be determined on a case by case basis.
(d)
Upstream concentrations
(Cs). The representative upstream concentration of phosphorus shall be
used in specific water quality based effluent limit calculations. The
representative upstream concentration shall be a concentration derived by the
department based on data from the specific stream or from a similar location.
Where data are collected on the upstream location, the site's upstream
concentration shall be calculated as a median using the procedures specified in
s. NR 102.07 (1) (b) to (c). Neither the two-sided 80 percent confidence
interval around the median specified in s. NR 102.07 (2) nor the combined
assessment procedures specified in s. NR 102.60 are applicable for purposes in
this paragraph. Upstream concentrations may not be measured at a location
within the direct influence of a point source discharge. The determination of
upstream concentrations shall be evaluated at each permit reissuance.
Note: The department has guidance on
collection methods for ambient water sampling and may develop guidance for the
evaluation of representative data. The guidance may be obtained from the
offices of the department of natural resources, bureau of water quality at 101
South Webster Street, P.O. Box 7921, Madison, Wisconsin
53707.
(3)
DISCHARGES TO INLAND LAKES AND RESERVOIRS. For discharges of
phosphorus directly to inland lakes, reservoirs, and other receiving waters
which do not exhibit a unidirectional flow at the point of discharge, the
department shall set the effluent limit equal to the criterion for the
receiving water or the downstream water.
Note: As described in s. NR 217.16, effluent
limitations for discharges to lakes may also be based on the wasteload
allocation of a total maximum daily load, where the total maximum daily load
has been approved by US EPA.
(4) DISCHARGES DIRECTLY TO GREAT LAKES. For
discharges directly to the Great Lakes, the department shall set effluent
limits consistent with nearshore or whole lake model results approved by the
department. The department may set an interim effluent limit based on the best
readily available phosphorus removal technology commonly used in Wisconsin.
Note: At the time this rule was promulgated,
December 1, 2010, the best readily available phosphorus removal technology
indicates a limit of 0.6 mg/L.
(5) OTHER METHODS OF LIMIT CALCULATION. The
department may use other models and equations for calculating a water quality
based effluent limitation if, in the best professional judgment of the
department, the model provides a more accurate representation of the
conditions.
(6) MULTIPLE
DISCHARGES.
(a) Except as provided in par.
(b), whenever the department determines that more than one discharge may be
affecting the water quality of the same receiving water, the resultant combined
allowable load shall be divided among the various discharges using an
allocation method based on site-specific considerations. Whenever the
department makes a determination under this subsection, the department shall
notify all permittees who may be affecting the water quality of the same
receiving water of the determination and any limitations developed under this
subsection. Permittees shall be given the opportunity to comment to the
department on any determination made under this subsection.
(b) This subsection does not apply if there
is a US EPA approved TMDL for phosphorus for the receiving water. If there is a
US EPA approved TMDL, the combined allowable load shall be divided in
accordance with the approved TMDL.
(7) MINIMUM EFFLUENT
LIMITATIONS. If the water quality based effluent limitation
calculated pursuant to the procedures in this section is less than the
phosphorus criterion specified in s. NR 102.06 for the water body, the effluent
limit shall be set to be equal to the criterion.
(8) NEW DISCHARGERS. If a
new discharger is proposing a discharge of phosphorus to a receiving or
downstream water that is a phosphorus impaired water, the new discharger may
not discharge phosphorus except as follows:
(a) The new discharge of phosphorus is
allocated part of the reserve capacity or part of the wasteload allocation in a
US EPA approved TMDL;
(b) The new
discharger can demonstrate the new discharge of phosphorus will improve water
quality in the phosphorus impaired segment; or
(c) The new discharger can demonstrate that
the new phosphorus load will be offset through a phosphorus trade or other
means with another discharge of phosphorus to the 303 (d) listed water. The
offset must be approved by the department and must be implemented prior to
discharge.
Section
283.84,
Stats., establishes requirements for pollutant
trades.
