NR 217.13
NR 217.13 Calculation of water quality based effluent limitations for phosphorus. NR 217.13(1)(a)(a) The department shall calculate potential water quality based effluent limitations for point source dischargers of phosphorus using the procedures in this section.
NR 217.13(1)(b)
(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.
NR 217.13(2)(a)
(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:
Limitation = [(WQC) (Qs+(1-f)Qe) - (Qs- fQe) (Cs)]/Qe
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f = Fraction of the effluent flow that is withdrawn from the receiving water, and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).
NR 217.13(2)(b)
(b) Receiving water design flow (Qs). Based on the availability of information and the professional judgment of the department, the value of Q
s to be used in calculating the effluent limitation for discharges to flowing waters shall be determined using one of the following:
NR 217.13(2)(b)1.
1. The average minimum 7-day flow which occurs once every 2 years (7-day Q
2) 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.
NR 217.13(2)(b)2.
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 Q
3) 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.
NR 217.13(2)(b)3.
3. Other flow deemed more representative of flow conditions and approved by the department.
NR 217.13(2)(c)1.1. For dischargers subject to ch.
NR 210 and which discharge for 24 hours per day on a year-round basis, Q
e 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.
NR 217.13(2)(c)2.
2. For other dischargers not subject to ch.
NR 210, Q
e shall equal, based on the best professional judgment of the department, one of the following:
NR 217.13(2)(c)2.a.
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.
NR 217.13(2)(c)2.b.
b. The maximum effluent flow, expressed as a 30 day rolling average, which has occurred for 30 continuous days and represents normal operations.
NR 217.13(2)(c)3.
3. For seasonal discharges, discharges proportional to stream flow, or other non-continuous discharge situations, Q
e shall be determined on a case by case basis.
NR 217.13(2)(d)
(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.
NR 217.13 Note
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.
NR 217.13(3)
(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.
NR 217.13 Note
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.
NR 217.13(4)
(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.
NR 217.13 Note
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.
NR 217.13(5)
(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.
NR 217.13(6)(a)(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.
NR 217.13(6)(b)
(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.
NR 217.13(7)
(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.
NR 217.13(8)
(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:
NR 217.13(8)(a)
(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;
NR 217.13(8)(b)
(b) The new discharger can demonstrate the new discharge of phosphorus will improve water quality in the phosphorus impaired segment; or
NR 217.13(8)(c)
(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.
NR 217.13 Note
Note: Section
283.84, Stats., establishes requirements for pollutant trades.
NR 217.13 History
History: CR 10-035: cr.
Register November 2010 No. 659, eff. 12-1-10;
CR 19-094: am. (2) (d) Register September 2022 No. 801, eff. 10-1-22; correction in (2) (d) made under s. 35.17, Stats., Register September 2022 No. 801.
NR 217.14
NR 217.14 Expression of limitations. NR 217.14(1)(a)(a) Water quality based effluent limitations, when required pursuant to s.
NR 217.15, shall be expressed in a discharge permit as a concentration. A mass limit shall also be included in a permit for discharges of phosphorus to any of the following receiving or downstream waters:
NR 217.14(1)(b)
(b) The department may establish mass limitations in permits for any other discharges of phosphorus if a concentration limit for phosphorus is included in the permit, and where an increase in phosphorus load is likely to result in adverse effects on water quality in the receiving water or downstream water.
NR 217.14(1)(c)
(c) For discharges to lakes, the department shall also include an annual mass limit for phosphorus in the permit.
NR 217.14(1)(d)
(d) If there is a US EPA approved TMDL for the receiving water, the department shall include a mass limit expressed in the manner consistent with the requirements of the TMDL. As provided in s.
NR 217.16, this TMDL based mass limit may be included in the permit in addition to, or in lieu of the mass limit established pursuant to this section.
NR 217.14 Note
Note: In accordance with s.
283.84, Stats., the department may approve the use of phosphorus trading as a means for a point source to achieve compliance with the water quality based effluent limitation, including a TMDL based limitation. The trade shall be incorporated into the terms of the WPDES permit for the point source and must be approved by the department prior to implementation.
NR 217.14(2)
(2)
Concentration based limitations. Concentration effluent limitations calculated under s.
NR 217.13 shall be expressed as a monthly average in permits, except for concentrations of less than or equal to 0.3 mg/L for which limitations may be expressed as six-month averages. If a concentration limitation expressed as a six-month average is included in a permit, a monthly average concentration limitation equal to three times the water based effluent limitation calculated under s.
NR 217.13 shall also be included in the permit.
NR 217.14(3)
(3)
Mass based limitations. Concentration effluent limitations calculated under s.
NR 217.13 shall be converted into mass effluent limitations using the effluent flow identified in s.
NR 217.13 and an appropriate conversion factor, and expressed as a monthly average in the permit, except for concentration based limitations of less than or equal to 0.3 mg/L for which mass limitations may be expressed as six-month averages.
NR 217.14 History
History: CR 10-035: cr.
Register November 2010 No. 659, eff. 12-1-10;
CR 15-085: am. (2), (3)
Register August 2016 No. 728, eff. 9-1-16.
NR 217.15
NR 217.15 Determination of necessity for water quality based effluent limitations for phosphorus. NR 217.15(1)(a)
(a)
General. The department shall include a water quality based effluent limitation for phosphorus in a permit whenever the discharge or discharges from a point source or point sources contain phosphorus at concentrations or loadings which will cause, has the reasonable potential to cause or contribute to, an exceedance of the water quality standards in s.
NR 102.06 in either the receiving water or downstream waters. The department shall use the procedures in this section to make this determination.
NR 217.15(1)(b)
(b) Permittees with existing phosphorus limitations. If a permittee has a technology based phosphorus limitation in a permit that is less restrictive than a water quality based effluent limitation for phosphorus calculated pursuant to s.
NR 217.13, then the department shall include the water quality based effluent limitation in the permit.
NR 217.15(1)(c)
(c) Permittees without existing phosphorus limitations. If a permittee discharges phosphorus, but does not have a technology based
limitation for phosphorus in its permit, the department shall use the procedures in this paragraph to determine whether a discharge will cause, has the reasonable potential to cause or contribute to an exceedance of the phosphorus water quality criterion in s.
NR 102.06 in the receiving or downstream waters, and whether to include a water quality based effluent limit for phosphorus in the WPDES permit.
NR 217.15(1)(c)1.
1. Using at least 11 daily discharge concentrations of phosphorus, if the upper 99
th percentile of the 30 day average discharge concentration of phosphorus exceeds the potential phosphorus limitation calculated under s.
NR 217.13, then the water quality based effluent limitation for phosphorus shall be included in the WPDES permit. If the upper 99
th percentile of the 30 day average discharge concentration of phosphorus is less than the potential phosphorus limitation calculated under s.
NR 217.13, then a water quality based effluent limitation for phosphorus is not required in the WPDES permit. The upper 99
th percentile of available discharge concentrations shall be calculated pursuant to s.
NR 106.05 (5).
NR 217.15(1)(c)2.
2. If 11 daily discharge concentrations of phosphorus are not available for a permittee, then a water quality based effluent limitation for phosphorus shall be included in the permit when the mean of available effluent concentrations is greater than one-fifth of the limit.
NR 217.15(1)(c)3.
3. If no phosphorus effluent data is available for an existing permittee, the department may require phosphorus sampling as part of a permit application for reissuance to determine whether a water quality based effluent limit is necessary in the WPDES permit under par.
(a), or the department may use effluent data information from similar point sources to make the determination under par.
(a).
NR 217.15 Note
Note: The department will develop guidance regarding the administration of this section to ensure that permitted discharges with a reasonable potential to cause or contribute to exceedances of the applicable phosphorus water quality criterion in s.
NR 102.06 are identified.
NR 217.15(1)(d)
(d) Sampling. Prior to permit reissuance, a permittee discharging any phosphorus shall collect effluent samples of phosphorus at a frequency specified by the department in the permit application for reissuance.
NR 217.15(1)(e)
(e) New dischargers. The department shall include a water quality based phosphorus limitation in a permit for a new discharger if the department determines the new discharger will discharge phosphorus at concentrations or loadings which may cause or contribute to exceedances of the water quality criteria in s.
NR 102.06 in either the receiving water or downstream waters. To estimate the amount of phosphorus discharged by a new discharger, the department may consider projected discharge information from the permit applicant and phosphorus discharge information from similar sources.
NR 217.15(2)
(2) If the department determines a water quality based effluent limitation is not necessary in a permit based on the procedures in this section, the department may still require monitoring for phosphorus discharges.
NR 217.15 History
History: CR 10-035: cr.
Register November 2010 No. 659, eff. 12-1-10; correction in (1) (c) 1. made under s.
13.92 (4) (b) 7., Stats.,
Register November 2010 No. 659.
NR 217.16
NR 217.16 Relationship of WQBELs and TMDL based limitations. NR 217.16(1)(1)
In addition to a water quality based effluent limitation calculated pursuant to s.
NR 217.13, the department may derive a water quality based effluent limitation for phosphorus consistent with the wasteload allocation and assumptions of a US EPA approved TMDL that is designed to achieve water quality standards in ch.
NR 102. This TMDL based limitation may be included in a permit in addition to, or in lieu of, the water quality based limitation calculated under s.
NR 217.13. When deciding whether to use a TMDL based limit as a substitute for the limitation calculated under s.
NR 217.13, the department shall consider the following factors:
NR 217.16(1)(a)
(a) The degree to which nonpoint sources contribute phosphorus to the impaired water;
NR 217.16(1)(b)
(b) Whether waters upstream of the impaired waters are meeting the phosphorus criteria; and
NR 217.16(1)(c)
(c) Whether waters downstream of the impaired water are meeting the phosphorus criteria.
NR 217.16(2)
(2) If the phosphorus limitation based on an approved TMDL is less stringent than the water quality based effluent limitation calculated in s.
NR 217.13, the department may include the TMDL based limit in lieu of the limit calculated in s.
NR 217.13 if the limit calculated under s.
NR 217.13 has not yet taken effect. If the department includes the TMDL based limitation for phosphorus in the WPDES permit in lieu of the limit calculated in s.
NR 217.13, the TMDL based limit may remain in the permit for up to two permit terms to allow time for implementation of the TMDL, or the implementation period specified in the TMDL, whichever is less. The department may include a schedule of compliance to achieve a TMDL based limit if the department determines a schedule of compliance is necessary. If after two permit terms, the department determines the nonpoint source load allocation has not been substantially reduced, the department may
impose the more stringent water quality based effluent limitation calculated under s.
NR 217.13, or may include the TMDL based limitation for an additional permit term if the department determines there will be significant nonpoint source load reductions within the upcoming permit term. If the department decides to remove a TMDL based phosphorus limit from a permit and instead include a more stringent water quality based phosphorus limit in the permit calculated under s.
NR 217.13, the department may provide a schedule of compliance for the more stringent limit if the department determines additional time is needed for the permittee to comply with the revised limit. Such schedules shall require compliance as soon as possible, but in no case no more than five years from the date that the permit is reissued or modified to include the revised effluent limitations.
NR 217.16(3)
(3) If a phosphorus water quality based limit calculated under s.
NR 217.13 has already taken effect in a permit, the department may replace the limit with a less stringent TMDL based limit, if allowed pursuant to antidegradation procedures in ch.
NR 207.
NR 217.16 Note
Note: The TMDL based limitation may be less stringent than the water quality based effluent limitation calculated under s.
NR 217.13 in cases where nonpoint sources are the significant phosphorus sources responsible for the impairment.
NR 217.16(4)
(4) If the phosphorus limitation based on an approved TMDL is more stringent than the water quality based effluent limitation calculated under s.
NR 217.13, the department shall include the more stringent TMDL based limitation in the WPDES permit.
NR 217.16 History
History: CR 10-035: cr.
Register November 2010 No. 659, eff. 12-1-10.
NR 217.17(1)(a)(a) Except as provided in sub.
(4), the department may provide a schedule of compliance for a water quality based phosphorus limitation in a WPDES permit, where based on available information the department finds that:
NR 217.17(1)(a)1.
1. The schedule of compliance will lead to compliance with the water quality based effluent limitation as soon as possible; and
NR 217.17(1)(a)2.
2. The schedule of compliance is appropriate and necessary because the permittee cannot immediately achieve compliance with the water quality based effluent limitation based on existing operation of its treatment system.
NR 217.17 Note
Note: Before any compliance schedule is established in a permit pursuant to this subchapter, the department must make the finding in par (a).
NR 217.17(1)(b)
(b) In determining whether a compliance schedule is appropriate and determining the length of the compliance schedule, the department shall consider all of the following factors:
NR 217.17(1)(b)1.
1. Whether there is any need for modifications to the treatment facilities, operations or measures to meet the water quality based effluent limitation, and if so, how long it will take to implement the modifications. If the department determines that a permittee only needs to make operational changes to achieve compliance with a limitation, the compliance schedule shall be as brief as possible and only allow time for operational start-up adjustments.
NR 217.17(1)(b)2.
2. The amount of time the discharger has already had to meet the water quality based effluent limitation under prior permits.
NR 217.17(1)(b)3.
3. The extent to which the discharger has made good faith efforts to comply with the water quality based effluent limitation and other requirements in prior permits, if applicable.
NR 217.17(1)(b)4.
4. The extent to which the phosphorus removal process technologies have been developed and proven to be effective.
