Section 327 IAC 5-2-11.4 - Great Lakes system dischargers total maximum daily loads; wasteload allocations for point sources; load allocations for nonpoint sources; preliminary wasteload allocationsAuthority: IC 13-14-8; IC 13-14-9; IC 13-15-1-2; IC 13-15-2-1; IC 13-18-3
Affected: IC 13-11-2; IC 13-18-4-7; IC 13-18-4-8
Sec. 11.4.
(a) This subsection applies to the establishment of TMDLs for all pollutants and pollutant parameters in the Great Lakes system. Where specified, the following conditions also apply to WLAs calculated in the absence of TMDLs and to preliminary WLAs:(1) At a minimum, TMDLs shall be established in accordance with the listing and priority setting process established in Section 303(d) of the Clean Water Act (CWA) and at 40 CFR 130.7. Where water quality standards cannot be attained immediately, TMDLs must reflect reasonable assurances that water quality standards will be attained in a reasonable period of time. TMDLs may be based on attaining water quality standards over a period of time, with specific controls on individual sources being implemented in stages. 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, the following: (A) Receiving water characteristics.(B) Persistence, behavior, and ubiquity of pollutants of concern.(C) Type of remediation activities necessary.(D) Available regulatory and nonregulatory controls.(E) Requirements for attainment of water quality standards.(2) An assessment and remediation plan that the commissioner has certified as meeting the requirements of this section pertaining to TMDLs and public participation requirements applicable to TMDLs, and that has been approved by EPA as meeting those requirements under 40 CFR 130.6, may be used in lieu of a TMDL for purposes of this section. Assessment and remediation plans under this section may include, but are not limited to, the following: (A) Lakewide Management Plans.(B) Remedial Action Plans.(C) State Water Quality Management Plans. Also, any part of an assessment and remediation plan that also satisfies one (1) or more requirements under Section 303(d) of the CWA or implementing regulations may be incorporated by reference into a TMDL as appropriate. Assessment and remediation plans under this section shall be tailored to the level of detail and magnitude for the watershed and pollutant being assessed.
(3) TMDLs, WLAs calculated in the absence of a TMDL, and preliminary WLAs must ensure attainment of applicable water quality standards including all numeric and narrative water quality criteria set forth in 327 IAC 2-1.5-8 and 327 IAC 2-1.516, and Tier I criteria and Tier II values established under 327 IAC 2-1.5-11 through 327 IAC 2-1.5-16.(4) If a discharge contains one (1) or more substances for which a TMDL, WLA calculated in the absence of a TMDL, or preliminary WLA was based on an HCC, HCV, HNC, or HNV, human health shall be protected from the potential adverse additive effects of mixtures of substances in an effluent in accordance with the following procedures: (A) If an effluent for a particular discharger contains more than one (1) substance for which an HCC exists or for which an HCC or an HCV can be calculated, the additivity of the mixture of carcinogens shall be addressed as follows:(i) Except as provided in item (ii), the TMDL, WLA calculated in the absence of a TMDL, or preliminary WLA based on an HCC or HCV shall be established to protect against additive effects possibly associated with simultaneous multiple chemical human exposure to carcinogens such that the following condition is met: Click here to view
Where: C = The adjusted TMDL, WLA calculated in the absence of a TMDL, or preliminary WLA concentration of each separate carcinogen that shall be used in the calculation of reasonable potential in section 11.5 of this rule and water quality-based effluent limitations (WQBELs) in section 11.6 of this rule.
WLA = The TMDL, WLA calculated in the absence of a TMDL, or preliminary WLA concentration based on the HCC or HCV for each respective carcinogen.
n = Number of WLAs based on an HCC or HCV.
(ii) Notwithstanding item (i): (AA) the commissioner may consider, upon submission of the discharger, the use of an alternate, scientifically-based, procedure for ensuring the aggregate risk of the mixture of carcinogens remains below one (1) in one hundred thousand (100,000); or(BB) if information is available to the commissioner demonstrating that available scientific information does not support the assumption of additivity, the TMDL, WLA calculated in the absence of a TMDL, or preliminary WLA shall not be adjusted for each such substance.(B) If an effluent for a particular discharger contains more than one (1) substance for which an HNC exists or for which an HNC or HNV can be calculated, the additivity of the mixture of substances shall be addressed as follows: (i) The incremental adverse effect of each substance shall be assumed to not be additive except as provided in item (ii).(ii) If scientific information available to the commissioner demonstrates that the adverse effects of the components are additive, the TMDL, WLA calculated in the absence of a TMDL, or preliminary WLA based on an HNC or HNV for each additive noncarcinogenic substance shall be established to protect against additive effects possibly associated with simultaneous multiple chemical human exposure such that the following condition is met: Click here to view
Where: N = The adjusted TMDL, WLA calculated in the absence of a TMDL, or preliminary WLA concentration of each separate additive noncarcinogenic substance that shall be used in the calculation of reasonable potential in section 11.5 of this rule and WQBELs in section 11.6 of this rule.
WLA = The TMDL, WLA calculated in the absence of a TMDL, or preliminary WLA concentration based on the HNC or HNV for each respective additive noncarcinogenic substance.
n = Number of WLAs based on an HNC or HNV for additive noncarcinogenic substances.
(C) Notwithstanding clauses (A) and (B), the toxicity equivalency factors (TEFs) and bioaccumulation equivalency factors (BEFs) for the chlorinated dibenzo-p-dioxins (CDDs) and chlorinated dibenzofurans (CDFs) shall be accounted for as follows: (i) The TEFs and BEFs in Table 11.4-1 in item (iv) shall be used when calculating a 2,3,7,8-TCDD toxicity equivalence concentration in effluent to be used when implementing both HNC and HCC. The chemical concentration of each CDDs and CDFs in effluent shall be converted to a 2,3,7,8-TCDD toxicity equivalence concentration in effluent by: (AA) multiplying the chemical concentration of each CDDs and CDFs in the effluent by the appropriate TEF in Table 11.4-1 in item (iv);(BB) multiplying each product from subitem (AA) by the BEF for each CDDs and CDFs in Table 11.4-1 in item (iv); and(CC) adding all final products from subitem (BB).(ii) The equation for calculating the 2,3,7,8-TCDD toxicity equivalence concentration in effluent is: Click here to view
Where: (TEC)tcdd = 2,3,7,8-TCDD toxicity equivalence concentration in effluent.
(C) x = Concentration of total chemical x in effluent.
(TEF) x = TCDD toxicity equivalency factor for x.
(BEF) x = TCDD bioaccumulation equivalency factor for x.
(iii) The 2,3,7,8-TCDD toxicity equivalence concentration in effluent shall be used when developing TMDLs, WLAs in the absence of a TMDL, or preliminary WLAs under this section.(iv) The following values shall be used for TEFs and BEFs for CDDs and CDFs: Table 11.4-1 |
Toxicity Equivalency Factors (TEF) and Bioaccumulation Equivalency Factors (BEF) for CDDs and CDFs |
Congener | TEF | BEF |
2,3,7,8-TCDD | 1.0 | 1.0 |
1,2,3,7,8-PeCDD | 0.5 | 0.9 |
1,2,3,4,7,8-HxCDD | 0.1 | 0.3 |
1,2,3,6,7,8-HxCDD | 0.1 | 0.1 |
1,2,3,7,8,9-HxCDD | 0.1 | 0.1 |
1,2,3,4,6,7,8-HpCDD | 0.01 | 0.05 |
OCDD | 0.001 | 0.01 |
2,3,7,8-TCDF | 0.1 | 0.8 |
1,2,3,7,8-PeCDF | 0.05 | 0.2 |
2,3,4,7,8-PeCDF | 0.5 | 1.6 |
1,2,3,4,7,8-HxCDF | 0.1 | 0.08 |
1,2,3,6,7,8-HxCDF | 0.1 | 0.2 |
2,3,4,6,7,8-HxCDF | 0.1 | 0.7 |
1,2,3,7,8,9-HxCDF | 0.1 | 0.6 |
1,2,3,4,6,7,8-HpCDF | 0.01 | 0.01 |
1,2,3,4,7,8,9-HpCDF | 0.01 | 0.4 |
OCDF | 0.001 | 0.02 |
(5) TMDLs shall include WLAs for point sources and LAs for nonpoint sources, including natural background, such that the sum of these allocations is not greater than the loading capacity of the water for the pollutant addressed by the TMDL, minus the sum of a specified margin of safety (MOS) and any capacity reserved for future growth. The components of the TMDL are as follows: (A) Nonpoint source LAs that shall be based on any of the following: (i) Existing pollutant loadings if changes in loadings are not reasonably anticipated to occur.(ii) Increases in pollutant loadings that are reasonably anticipated to occur.(iii) Anticipated decreases in pollutant loadings if such decreased loadings are technically feasible and are reasonably anticipated to occur within a reasonable time period as a result of implementation of BMPs or other load reduction measures. In determining whether anticipated decreases in pollutant loadings are technically feasible and can reasonably be expected to occur within a reasonable period of time, technical and institutional factors shall be considered. These decisions are case-specific and should reflect the particular TMDL under consideration.(iv) Where appropriate and where sufficient data are available, contributions to the water column from sediments inside and outside of any applicable mixing zones.(v) Where appropriate and where sufficient data are available, nonpoint source discharges resulting from wet weather events. Monitoring data for these LAs shall be collected and analyzed in order to validate the TMDL's assumptions, to verify anticipated load reductions, to evaluate the effectiveness of controls being used to implement the TMDL, and to revise the WLAs and LAs as necessary to ensure that water quality criteria shall be achieved within the time period established in the TMDL.
(B) Each TMDL shall include an MOS sufficient to account for technical uncertainties in establishing the TMDL and shall describe the manner in which the MOS is determined and incorporated into the TMDL. The MOS may be provided by leaving a portion of the loading capacity unallocated or by using conservative modeling assumptions to establish WLAs and LAs. If a portion of the loading capacity is left unallocated to provide an MOS, the amount left unallocated shall be described. If conservative modeling assumptions are relied on to provide an MOS, the specific assumptions providing the MOS shall be identified.(C) TMDLs may include reserved allocations of loading capacity to accommodate future growth and additional sources. Where such reserved 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 shall not be allowed unless the TMDL is revised in accordance with these procedures to include an allocation for the new or expanded discharge.(D) The sum of the WLAs is the portion of the loading capacity not assigned to nonpoint sources including background, or to an MOS, or reserved for future growth. Where appropriate and where sufficient data are available, WLAs shall also be developed for point source discharges resulting from wet weather events. Upon reissuance, NPDES permits for these point sources must include effluent limitations consistent with WLAs in EPA-approved or EPA-established TMDLs.(6) If separate TMDLs are prepared for different segments of the same watershed, and the separate TMDLs each include WLAs for the same pollutant for one (1) or more of the same point sources, then WQBELs for that pollutant for the point sources shall be consistent with the most stringent of those WLAs in order to ensure attainment of all applicable water quality standards.(7) TMDLs shall be sufficiently stringent so as to prevent accumulation of the pollutant of concern in sediments to levels injurious to designated or existing uses, human health, wildlife, and aquatic life.(8) The representative background concentration of pollutants shall be established in accordance with this section to develop TMDLs, WLAs calculated in the absence of a TMDL, and preliminary WLAs. Background loadings may be accounted for in a TMDL through an allocation to a single background category or through individual allocations to the various background sources as follows:(A) As used in this subsection, "background" represents all loadings resulting from the following:(i) Flow from upstream waters into the specified watershed, waterbody, or waterbody segment for which a TMDL, WLA in the absence of a TMDL, or preliminary WLA for the purpose of determining the need for a WQBEL is being developed.(ii) Atmospheric deposition or sediment release or resuspension.(iii) Chemical reactions occurring within the watershed, waterbody, or waterbody segment.(B) When determining what available data are acceptable for use in calculating background, the commissioner shall use best professional judgment, including consideration of the sampling location and the reliability of the data through comparison to reported analytical detection levels. Pollutant degradation and transport information may be considered when utilizing pollutant loading data. Where limited or no acceptable data exist, the commissioner may require the permittee to supply the necessary data. Best professional judgment shall be used to select the one (1) data set that most accurately reflects or estimates background concentrations when data in more than one (1) of the following data sets or categories exist:(i) Acceptable available water column data.(ii) Water column concentrations estimated through use of acceptable available caged or resident fish tissue data.(iii) Water column concentrations estimated through use of acceptable available or projected pollutant loading data.(C) The representative background concentration for a substance in the specified watershed, waterbody, or waterbody segment shall be established as follows: (i) If all the values in the data set selected in clause (B) are at or above the LOD, then the background concentration is the geometric mean of that data set.(ii) If the data set consists of values above and below the LOD, the following procedure shall be used to determine the representative background concentration:(AA) Each value in the data set with a value less than the LOD (nondetect) shall be assigned the value (V). The geometric mean of this adjusted data set is the representative background concentration. The value (V) is determined as follows: Click here to view
(BB) If information is available that indicates an alternate methodology for evaluating the data set would result in a background concentration more representative of actual conditions, this alternative methodology may be used in place of the methodology contained in subitem (AA) upon approval of the commissioner.(iii) When all of the acceptable available data in a data set or category, such as water column, caged or resident fish tissue, or pollutant loading data, are below the LOD for a substance, and the most sensitive approved analytical method available for that substance was used, then all the data for that pollutant in that data set shall be assumed to be zero (0).(iv) Notwithstanding items (i) through (iii), the representative background concentration of whole effluent toxicity (WET) shall be assumed to be zero (0) unless data are available that indicates that the discharge of the WET and any background WET are additive.(9) The effluent flow used to develop TMDLs, WLAs calculated in the absence of a TMDL, and preliminary WLAs shall be determined as follows: (A) For municipal, semipublic, and other sanitary or domestic wastewater discharges, the average design flow of the treatment facility shall be used.(B) For industrial dischargers, the highest monthly average flow from the previous two (2) years of monitoring shall be used.(C) Notwithstanding clauses (A) and (B), an alternate effluent flow value may be used, upon approval by the commissioner, if the discharger provides flow data that supports the alternate value (such as when a TMDL or WLA is calculated for wet weather conditions as provided in section 11.6(g)(4) of this rule). This flow data shall be included with the application for a new permit, a renewal of an existing permit, or with a request for modification of an existing permit, or when requested by the commissioner.(D) TMDLs, WLAs calculated in the absence of a TMDL, and preliminary WLAs shall indicate the point source effluent flows used in the analyses.(10) The portion of the receiving waterbody allocated for mixing for TMDLs, WLAs calculated in the absence of a TMDL, and preliminary WLAs shall be determined in accordance with subsection (b).(11) TMDLs, WLAs in the absence of a TMDL, and preliminary WLAs shall be based on the assumption that a pollutant does not degrade. However, the commissioner may take into account degradation of the pollutant if each of the following conditions are met: (A) Scientifically valid field studies or other relevant information demonstrate that degradation of the pollutant is expected to occur under the full range of environmental conditions expected to be encountered.(B) Scientifically valid field studies or other relevant information addresses other factors that affect the level of pollutants in the water column, including, but not limited to, the following:(i) Resuspension of sediments.(ii) Chemical speciation.(iii) Biological and chemical transformation.(C) Notwithstanding clauses (A) and (B), TMDLs, WLAs in the absence of a TMDL, and preliminary WLAs conducted for chlorine and WET shall be based on the assumption that the parameter does degrade unless data for the waterbody are available indicating otherwise.(12) As used in this section, "loading capacity" refers to the greatest amount of loading that a water can receive without violating water quality standards. The loading capacity is initially calculated at the farthest downstream location in the watershed drainage basin. The maximum allowable loading consistent with the attainment of each applicable numeric criterion or value for a given pollutant is determined by multiplying the applicable criterion or value by the flow at the farthest downstream location in the tributary basin at the design flow condition described under subsection (b) and by using appropriate conversion factors. This loading is then compared to the loadings at sites within the basin to assure that applicable numeric criteria or values for a given pollutant are not exceeded at all applicable sites. The lowest load is then selected as the loading capacity.(13) The ambient water quality characteristics used to develop TMDLs, WLAs calculated in the absence of a TMDL, and preliminary WLAs shall be determined as follows: (A) For ammonia (as N), chloride, metals dependent on hardness, and pentachlorophenol, the appropriate water quality characteristics shall be obtained at a location downstream of the point of discharge, or for Lake Michigan, outside the applicable mixing zone and shall be determined as follows:(i) For ammonia (as N), the seventy-fifth percentile of the pH and temperature. If a seasonal TMDL, WLA calculated in the absence of a TMDL, or preliminary WLA is developed for ammonia, the pH and temperature data shall be obtained from the appropriate seasonal period.(ii) For chloride, the fiftieth percentile of the hardness and sulfate.(iii) For metals dependent on hardness, the fiftieth percentile of the hardness.(iv) For pentachlorophenol, the fiftieth percentile of the pH.(B) If any of the data required under clause (A) are not available for the waterbody, the data shall either be obtained from similar nearby streams or the permittee will be required to obtain the necessary data. For discharges to Lake Michigan, data from Lake Michigan shall be required.(C) The use of the data required in clause (A) is intended to determine values of those water quality characteristics that are representative of those characteristics at design conditions. If it is demonstrated that an alternate method of determining these characteristics for a specific receiving waterbody would result in values more representative of the characteristics at design conditions, then this alternate method may be used to determine the water quality characteristics.(b) The following requirements shall be applied in establishing the portion of the receiving waterbody allocated for mixing for TMDLs, WLAs in the absence of TMDLs, and preliminary WLAs: (1) The following procedures shall be used to establish the portion of the receiving waterbody allocated for mixing for TMDLs, WLAs in the absence of TMDLs, and preliminary WLAs for a BCC: (A) For purposes of this subsection, new and existing discharges are determined as follows: (i) New discharges are defined as: (AA) discharges from new Great Lakes dischargers; or(BB) new or expanded discharges from an existing Great Lakes discharger.(ii) Existing discharges are defined as all discharges of BCCs not included in item (i).(B) There shall be no mixing zone available for a new discharge of a BCC to the Great Lakes system. WLAs established through TMDLs, WLAs in the absence of TMDLs, and preliminary WLAs for a new discharge of a BCC shall be set equal to the most stringent applicable water quality criteria or values for the BCC.(C) A mixing zone may be allocated for a BCC for an existing discharge to the Great Lakes system under subdivisions (2) and (3) until January 1, 2004, except for a discharge into the open waters of Lake Michigan. WLAs established through TMDLs, WLAs established in the absence of TMDLs, and preliminary WLAs for all discharges, both new and existing, into the open waters of Lake Michigan shall be set equal to the most stringent applicable water quality criteria or values for the BCC.(D) Except as provided in clauses (E) and (F), NPDES permits shall not authorize mixing zones for existing discharges of a BCC to the Great Lakes system after January 1, 2004. After January 1, 2004, WLAs established through TMDLs, WLAs established in the absence of TMDLs, and preliminary WLAs for all discharges of a BCC to the Great Lakes system shall be set equal to the most stringent applicable water quality criteria or values for the BCC.(E) The commissioner may grant mixing zones for any existing discharge of a BCC to the Great Lakes system beyond the date specified in clause (D) where it can be demonstrated, on a case-by-case basis, that failure to grant a mixing zone would preclude water conservation measures that would lead to the overall load reduction of the BCC, even though higher concentrations of the BCC occur in the effluent. Such mixing zones must also be consistent with subdivisions (2) and (3).(F) The commissioner may grant mixing zones, consistent with subdivisions (2) and (3), beyond the date specified in clause (D) for any existing discharge of a BCC to the Great Lakes system upon the request of a discharger subject to the following limited circumstances: (i) The commissioner determines the following:(AA) The discharger is in compliance with and will continue to implement all applicable technologybased treatment and pretreatment requirements of Sections 301, 302, 304, 306, 307, 401, and 402 of the CWA, and is in compliance with its existing NPDES WQBELs, including those based on a mixing zone.(BB) The discharger has reduced and will continue to reduce the loading of the BCC for which a mixing zone is requested to the maximum extent possible.(ii) In making the determination in item (i), the commissioner shall consider the following information submitted by the discharger:(AA) The availability, feasibility, cost effectiveness, and environmental benefits of additional controls or pollution prevention measures for reducing and ultimately eliminating the BCC for that discharger, including those used by similar dischargers. As used in this item, "pollution prevention" has the meaning set forth in the federal Pollution Prevention Act of 1990 (42 U.S.C. 13101 et seq.).(BB) Whether the discharger or affected communities will suffer unreasonable economic effects if the mixing zone is eliminated.(CC) The extent to which the discharger will implement an ambient monitoring plan to ensure compliance with water quality criteria at the edge of any authorized mixing zone or to ensure consistency with any applicable TMDL or such other strategy consistent with this section.(DD) Other information the commissioner deems appropriate.(iii) Any exceptions to the mixing zone elimination provision for an existing discharge of a BCC granted under this clause shall comply with the following:(AA) Not result in any less stringent limitations than those existing upon or after the effective date of this rule.(BB) Not likely jeopardize the continued existence of any endangered or threatened species listed under Section 4 of the ESA or result in the destruction or adverse modification of such species' critical habitats.(CC) Be limited to one (1) permit term unless the commissioner makes a new determination in accordance with this subdivision for each successive permit application in which a mixing zone for the BCC is sought.(DD) Reflect all information relevant to the size of the mixing zone considered under item (ii).(EE) Protect all designated and existing uses of the receiving water.(FF) Meet all applicable aquatic life, wildlife, and human health criteria and values at the edge of the mixing zone and, as appropriate, within the mixing zone or be consistent with any appropriate TMDL or such other strategy consistent with this section.(GG) Ensure the discharger has developed and conducted a pollutant minimization program for the BCC if required to do so under section 11.6 of this rule.(HH) Ensure that alternative means for reducing BCCs elsewhere in the watershed are evaluated.(G) For each draft NPDES permit that would allow a mixing zone for one (1) or more BCCs after January 1, 2004, the fact sheet or statement of basis for the draft permit, shall: (i) specify the mixing provisions used in calculating the permit limits; and(ii) identify each BCC for which a mixing zone is proposed.(2) The following addresses conditions for deriving TMDLs, WLAs in the absence of TMDLs, and preliminary WLAs for open waters of Lake Michigan, inland lakes, and other waters of the Great Lakes system with no appreciable flow relative to their volumes: (A) For discharges into the open waters of Lake Michigan, the following requirements apply: (i) To prevent acute toxicity to aquatic life, WLAs established in a TMDL, WLAs in the absence of a TMDL, and preliminary WLAs shall be determined as follows: (AA) For allocations based on an acute aquatic life criterion or value, the CMC or SMC shall not be exceeded outside the zone of initial dilution and the FAV shall not be exceeded in the undiluted discharge, unless a mixing zone demonstration is conducted and approved under subdivision (4), in which case the CMC or SMC shall be met outside the applicable alternate mixing zone.(BB) For allocations implementing the narrative acute WET criterion, one and zero-tenths (1.0) TUa shall not be exceeded in the undiluted discharge, unless a mixing zone demonstration is conducted and approved under subdivision (4), in which case three-tenths (0.3) TUa shall be met outside the applicable alternate mixing zone.(ii) To prevent chronic toxicity to aquatic life, human health, and wildlife, WLAs established in a TMDL, WLAs in the absence of a TMDL, and preliminary WLAs shall be determined as follows: (AA) For allocations based on a chronic criterion or value (CCC or SCC; HNC or HNV; HCC or HCV; or WC or WV), the chronic criterion or value shall not be exceeded in the undiluted discharge unless a mixing zone demonstration is conducted and approved under subdivision (4), in which case the chronic criterion or value shall be met outside the applicable alternate mixing zone.(BB) For allocations implementing the narrative chronic WET criterion, one and zero-tenths (1.0) TUc shall not be exceeded in the undiluted discharge unless a mixing zone demonstration is conducted and approved under subdivision (4), in which case one and zero-tenths (1.0) TUc shall be met outside the applicable alternate mixing zone.(iii) WLAs established in a TMDL, WLAs in the absence of a TMDL, and preliminary WLAs based on the criterion for chloride, sulfate, total dissolved solids, fluoride, or dissolved iron under 327 IAC 2-1.5-8(j) shall ensure that the criterion not be exceeded in the undiluted discharge unless a mixing zone demonstration is conducted and approved under subdivision (4), in which case the criterion shall be met outside the applicable alternate mixing zone.(iv) If mixing zones from two (2) or more proximate sources interact or overlap, the combined effect must be evaluated to ensure that applicable criteria and values will be met in the area where any applicable mixing zones overlap.(v) In no case shall a mixing zone be granted that exceeds the area where discharge-induced mixing occurs.(B) For discharges into inland lakes and other waters of the Great Lakes system with no appreciable flow relative to their volumes (other than the open waters of Lake Michigan), no mixing zone will be allowed and water quality criteria or values will apply to the undiluted discharge.(C) Appropriate mixing zone assumptions to be used in calculating load allocations for nonpoint sources shall be determined on a case-by-case basis.(D) In no case shall a mixing zone be granted that would likely jeopardize the continued existence of any endangered or threatened species listed under Section 4 of the ESA or result in the destruction or adverse modification of such species' critical habitats.(3) The following describes conditions for deriving TMDLs, WLAs in the absence of TMDLs, and preliminary WLAs for tributaries of the Great Lakes system that exhibit appreciable flows relative to their volumes: (A) The following stream design flows shall be used unless data exist to demonstrate that an alternative stream design flow is appropriate for stream-specific and pollutant-specific conditions: (i) For purposes of calculating a TMDL, WLAs in the absence of a TMDL, or preliminary WLAs, using a steady-state model, the stream design flows shall be as follows:(AA) For an acute aquatic life criterion or value, the one (1) day, ten (10) year stream design flow (Q1,10).(BB) To implement the narrative acute WET criterion, when a mixing zone demonstration is conducted and approved under subdivision (4), the one (1) day, ten (10) year stream design flow (Q1,10).(CC) For a chronic aquatic life criterion or value, the seven (7) day, ten (10) year stream design flow (Q7,10).(DD) To implement the narrative chronic WET criterion, the seven (7) day, ten (10) year stream design flow (Q7,10).(EE) For a drinking water human health criterion or value, the harmonic mean flow at the point of the public water system intake.(FF) For a nondrinking water human health criterion or value, the harmonic mean flow at the point of discharge.(GG) For a WC or WV, the ninety (90) day, ten (10) year stream design flow (Q90,10).(ii) TMDLs, WLAs in the absence of TMDLs, and preliminary WLAs calculated using dynamic modelling do not need to incorporate the stream design flows specified in item (i).(iii) TMDLs, WLAs in the absence of TMDLs, and preliminary WLAs calculated for intermittent or controlled discharges may use alternate stream design flows if these alternate design flows will ensure compliance with water quality criteria and values.(B) To prevent acute toxicity, WLAs and LAs established in a TMDL, WLAs in the absence of a TMDL, and preliminary WLAs shall be determined as follows:(i) For allocations based on an acute aquatic life criterion or value, the CMC or SMC shall not be exceeded outside the zone of initial dilution and the FAV shall not be exceeded in the undiluted discharge unless a mixing zone demonstration is conducted and approved under subdivision (4), in which case the CMC or SMC shall be met outside the applicable alternate mixing zone.(ii) For allocations implementing the narrative acute WET criterion, one and zero-tenths (1.0) TUa shall not be exceeded in the undiluted discharge unless a mixing zone demonstration is conducted and approved under subdivision (4), in which case three-tenths (0.3) TUa shall be met outside the applicable alternate mixing zone.(C) To protect aquatic life, wildlife, and human health from chronic effects, including chronic WET, WLAs and LAs established in a TMDL, WLAs in the absence of a TMDL, and preliminary WLAs shall be calculated using a dilution fraction no greater than twenty-five percent (25%) of the stream design flow unless a mixing zone demonstration under subdivision (4) is conducted and approved.(D) If mixing zones from two (2) or more proximate sources interact or overlap, the combined effect must be evaluated to ensure that applicable criteria and values will be met in the area where any applicable mixing zones overlap.(E) In no case shall a permitting authority grant a mixing zone that would likely jeopardize the continued existence of any endangered or threatened species listed under Section 4 of the ESA or result in the destruction or adverse modification of such species' critical habitats.(4) An alternate mixing zone that is allowed under subdivision (2) or (3) may be granted upon the request of the discharger subject to the following requirements:(A) Alternate mixing zones are granted on a pollutant-by-pollutant and criterion-by-criterion basis. Any discharger seeking a mixing zone other than that specified by subdivision (2) or (3) shall submit an application for an alternate mixing zone for consideration by the commissioner. The alternate mixing zone application must do the following:(i) Document the characteristics and location of the outfall structure, including whether technologically-enhanced mixing will be utilized.(ii) Document the amount of dilution occurring at the boundaries of the proposed mixing zone and the size, shape, and location of the area of mixing, including the manner in which diffusion and dispersion occur.(iii) For sources discharging to the open waters of Lake Michigan, define the location at which discharge-induced mixing ceases.(iv) For sources discharging to tributaries of the Great Lakes system that exhibit appreciable flows relative to their volumes and seeking an alternate mixing zone for an acute aquatic life criterion or value or for acute WET, define the location at which discharge-induced mixing ceases under stream design flow conditions.(v) Document the physical, including substrate character and geomorphology, chemical, and biological characteristics of the receiving waterbody, including whether the receiving waterbody supports indigenous, endemic, or naturally occurring species.(vi) Document the physical, chemical, and biological characteristics of the effluent.(vii) Document the synergistic effects of overlapping mixing zones or the aggregate effects of adjacent mixing zones.(viii) Show whether organisms would be attracted to the area of mixing as a result of the effluent character.(B) The commissioner may grant the alternate mixing zone if the discharger demonstrates the following:(i) The mixing zone would not interfere with or block passage of fish or aquatic life.(ii) The level of the pollutant permitted in the waterbody would not likely jeopardize the continued existence of any endangered or threatened species listed under Section 4 of the ESA or result in the destruction or adverse modification of such species' critical habitats.(iii) The mixing zone would not extend to drinking water intakes.(iv) The mixing zone would not impair or otherwise interfere with the designated or existing uses of the receiving water or downstream waters.(v) The mixing zone would not promote undesirable aquatic life or result in a dominance of nuisance species.(vi) By allowing the additional mixing:(AA) substances will not settle to form objectionable deposits;(BB) floating debris, oil, scum, and other matter in concentrations that form nuisances will not be produced; and(CC) objectionable color, odor, taste, or turbidity will not be produced.(C) In no case shall an alternate mixing zone for an acute aquatic life criterion or value or for acute WET be granted unless the discharger utilizes a submerged, high rate diffuser outfall structure (or the functional equivalent) that provides turbulent initial mixing and minimizes organism exposure time.(D) In no case shall an alternate mixing zone for an acute aquatic life criterion or value or for acute WET be granted that exceeds the area where discharge-induced mixing occurs.(E) In no case shall an alternate mixing zone for a discharge into the open waters of Lake Michigan be granted that exceeds the area where discharge-induced mixing occurs.(F) Upon receipt of an application for an alternate mixing zone, the commissioner shall provide notice, request comment, and, if requested, schedule and hold a public meeting on the application in accordance with section 11.2 of this rule.(5) Except for discharges into the open waters of Lake Michigan, notwithstanding subdivisions (2) through (4), the commissioner may deny any mixing zone for:(B) certain substances in a discharge; or(C) a criterion or value for any substance in a discharge; based upon a determination of adverse human health, aquatic life, or wildlife effects. The commissioner shall identify and document the rationale for this decision.
(6) For discharges into the open waters of Lake Michigan, if all of the conditions for approval of an alternate mixing zone are met in accordance with subdivision (4), the alternate mixing zone shall be granted unless the commissioner determines that the mixing zone should be denied based upon a consideration of harm to human health, aquatic life, or wildlife. The commissioner shall evaluate all available information, including information submitted by the public, relevant to the consideration of harm to human health, aquatic life, or wildlife. The commissioner shall identify the harm to human health, aquatic life, or wildlife, and document the rationale for this decision.(7) The commissioner's evaluation of a mixing zone for a discharge into the open waters of Lake Michigan under subdivisions (2), (4), and (6) shall constitute the evaluation required by IC 13-18-4-7. Any decision regarding the granting or denial of a mixing zone for a discharge into Lake Michigan shall be included in the public notice of the tentative decision on the draft new, renewed, or modified permit. The basis for the tentative decision, including the commissioner's rationale for concluding whether or not the requirements of IC 13-18-4-7 are satisfied, shall be included in the briefing memo or fact sheet that accompany the tentative decision on the draft new, renewed, or modified permit.(c) WLAs calculated in the absence of a TMDL and preliminary WLAs shall be determined using the conservation of mass equations as follows unless an alternate methodology is approved by the commissioner: (1) For the calculations contained within this subsection, the following apply:(A) WQCc = The chronic water quality criterion or value. A chronic water quality criterion or value is any of the following: (i) CCC or SCC. If the CCC or SCC for a metal is expressed in the form of dissolved metal, the CCC or SCC shall be set equal to Cinstream determined for the CCC or SCC in accordance with subdivision (6).(ii) The numeric interpretation of the narrative chronic WET criterion (one and zero-tenths (1.0) TUc).(vi) The criterion for chloride, sulfate, total dissolved solids, fluoride, or dissolved iron under 327 IAC 2-1.5-8(j).(B) WQCa = The CMC or SMC or, if a mixing zone demonstration for acute WET is conducted and approved under subsection (b)(4), three-tenths (0.3) TUa for WET. If the CMC or SMC for a metal is expressed in the form of dissolved metal, the CMC or SMC shall be set equal to Cinstream determined for the CMC or SMC in accordance with subdivision (8).(C) FAV = Two (2) times the CMC or SMC. If the CMC or SMC for a metal is expressed in the form of dissolved metal, the FAV shall equal two (2) times Cinstream determined for the CMC or SMC in accordance with subdivision (8).(D) Qe = The facility effluent flow as determined by subsection (a)(9).(E) Qw = The portion of the receiving waterbody allocated for mixing under subsection (b). If Cb is greater than the water quality criterion or value, a value of zero (0) shall be used for Qw.(F) Cb = The representative background concentration determined by subsection (a)(8).(H) Qz = The portion of the receiving waterbody allocated for mixing in the zone of initial dilution. For discharges into tributaries that exhibit appreciable flows relative to their volumes, Qz = Qe or the Q1, 10, whichever is less. For discharges into the open waters of Lake Michigan, Qz = Qe. If Cb is greater than WQCa, a value of zero (0) shall be used for Qz.(2) WLAs for discharges into tributaries that exhibit appreciable flows relative to their volumes based on protection from acute aquatic effects shall be determined as follows: (A) For a discharge without an approved alternate mixing zone under subsection (b)(4), the equation resulting in the lesser WLA shall be used:(i) WLA = FAV (or 1.0 TUa for WET); or(B) For a discharge with an approved alternate mixing zone under subsection (b)(4), the following equation shall be used: WLA = (WQCa)(DF) - (Cb)(DF-1)
(3) WLAs for discharges into tributaries that exhibit appreciable flows relative to their volumes based on protection from chronic effects shall be determined as follows: Click here to view
(4) WLAs for discharges into the open waters of Lake Michigan based on protection from acute aquatic effects shall be determined as follows: (A) For a discharge without an approved alternate mixing zone under subsection (b)(4), the equation resulting in the lesser WLA shall be used:(i) WLA = FAV (or 1.0 TUa for WET); or(B) For a discharge with an approved alternate mixing zone under subsection (b)(4), the following equation shall be used: WLA = (WQCa)(DF) - (Cb)(DF-1)
(5) WLAs for discharges into the open waters of Lake Michigan based on protection from chronic effects shall be determined as follows:(A) For a discharge without an approved alternate mixing zone under subsection (b)(4), the following equation shall be used: WLA = WQCc
(B) For a discharge with an approved alternate mixing zone under subsection (b)(4), the following equation shall be used: WLA = (WQCc)(DF) - (Cb)(DF-1)
(6) WLAs for discharges into inland lakes and other waters of the Great Lakes system with no appreciable flow relative to their volumes (other than the open waters of Lake Michigan) based on protection from acute aquatic effects shall be determined as follows: WLA = WQCa
(7) WLAs for discharges into inland lakes and other waters of the Great Lakes system with no appreciable flow relative to their volumes (other than the open waters of Lake Michigan) based on protection from chronic effects shall be determined as follows: WLA = WQCc
(8) The following procedures shall be used to calculate Cinstream, the total recoverable metal concentration outside the mixing zone that equates to an acute or chronic aquatic life water quality criterion or value expressed in the form of dissolved metal:(A) For a CMC or SMC expressed in the form of dissolved metal, Cinstream shall be calculated by dividing the CMC or SMC by the acute translator found in clause (D).(B) For a CCC or SCC expressed in the form of dissolved metal, Cinstream shall be calculated by dividing the CCC or SCC by the chronic translator found in clause (D).(C) If all approved analytical methods for the metal inherently measure only its dissolved form, such as hexavalent chromium, Cinstream shall not be calculated and the acute and chronic aquatic life water quality criteria or values expressed in the form of dissolved metal shall be used in the calculation of WLAs.(D) Unless a site-specific translator is determined in accordance with clause (E), the following translators shall be used: Table 11.4-2 |
Metals Translators |
Dissolved to Total Recoverable |
| Acute | Chronic |
Substances | Translators | Translators |
Arsenic (III) | 1.000 | 1.000 |
Cadmium | 1.136672-[(ln hardness)(0.041838)] | 1.101672-[(ln hardness)(0.041838)] |
Chromium (III) | 0.316 | 0.860 |
Copper | 0.960 | 0.960 |
Mercury | 0.85 | 0.85 |
Nickel | 0.998 | 0.997 |
Selenium | 0.922 | 0.922 |
Zinc | 0.978 | 0.986 |
(E) A discharger or proposed discharger may request the use of an alternate translator by using site-specific data. The discharger must conduct a site-specific study to identify the ratio of the dissolved fraction to the total recoverable fraction for a metal in the receiving waterbody outside the mixing zone. If the discharger provides an acceptable study, and other provisions of 327 IAC 2-1.5 and this article are satisfied (such as antibacksliding and antidegradation), the commissioner shall use the site-specific translator. A translator derived for one (1) discharge into a waterbody segment may be applied to other discharges on the same waterbody segment if the translator would adequately represent the site-specific conditions applicable to the other discharges.(d) Notwithstanding subsections (a) through (c), the pollutants contained in this subsection shall be addressed as follows: (1) The pH requirements contained in 327 IAC 2-1.5-8(c)(2) and 327 IAC 2-1.5-8(j) apply to the undiluted discharge.(2) The bacteriological criteria contained in 327 IAC 2-1.5-8(e) apply to the undiluted discharge.(3) Models, approved by the commissioner, that ensure compliance with the applicable water quality criteria for the following parameters shall be used: (A) Dissolved oxygen criteria contained in 327 IAC 2-1.5-8(c)(3), 327 IAC 2-1.5-8(d)(1), and 327 IAC 2-1.5-8(j).(B) Thermal requirements contained in 327 IAC 2-1.5-8(c)(4) and 327 IAC 2-1.5-8(d)(2).(C) Criteria for the protection of public water supplies contained under 327 IAC 2-1.5-8(f).(D) Criteria for the protection of industrial water supplies contained in 327 IAC 2-1.5-8(g).Water Pollution Control Board; 327 IAC 5-2-11.4; filed Jan 14, 1997, 12:00 p.m.: 20 IR 1441; errata filed Aug 11, 1997, 4:15 p.m.: 20 IR 3379; filed Feb 14, 2005, 10:05 a.m.: 28 IR 2102; errata filed Jul 6, 2005, 3:12 p.m.: 28 IR 3582; filed Jul 9, 2012, 2:54 p.m.: 20120808-IR-327110320FRAReadopted filed 10/18/2024, 1:57 p.m.: 20241113-IR-327230810RFA