Ohio Administrative Code
Title 3745 - Ohio Environmental Protection Agency
Chapter 3745-2 - Attainment and Protection of Surface Water Quality Standards (WQS)
Section 3745-2-12 - Total maximum daily loads

(1) At a minimum, total maximum daily loads (TMDLs) shall be established in accordance with the listing and priority setting process established in Section 303(d) of the act and 40 C.F.R. 130.7.

(2) The director shall do the following for stakeholder involvement during TMDL development in accordance with section 6111.562 of the Revised Code:

(3) Official draft TMDL. The director shall prepare an official draft TMDL prior to establishing a final TMDL, as follows:

(4) Final TMDL. After completion of the items in paragraph (A)(3) of this rule if the director determines it is appropriate to complete the TMDL, the director shall establish a final TMDL and submit the final TMDL to U.S. EPA for approval. A final TMDL may be challenged in accordance with section 6111.564 of the Revised Code.

(5) TMDL modifications. The director may modify an official draft, final or U.S. EPA approved TMDL. A modification, other than a modification to a draft or final TMDL consistent with comments received, is subject to the requirements in paragraph (A)(3) of this rule.

(6) Where a TMDL is not required by paragraph (A)(1) of this rule or it is not technically feasible to complete development of a TMDL prior to NPDES permit issuance or renewal deadlines for a discharge to a TMDL assessment area, Ohio EPA may develop water quality based effluent limits (WQBELs) for a discharge in the absence of a TMDL pursuant to rules 3745-2-04 to 3745-2-11 of the Administrative Code.

(1) At a minimum, the following factors shall be considered when determining an assessment area for a TMDL:

(2) A TMDL shall be determined as the sum of all existing or projected loads of a pollutant to the TMDL assessment area from point sources, nonpoint sources and background sources. The sum of the loads shall not be greater than the loading capacity of the receiving water for the pollutant minus a specified margin of safety (MOS) and any capacity reserved for future growth.

(3) The background concentration of a pollutant for the purpose of establishing a TMDL shall be determined in accordance with rule 3745-2-05 of the Administrative Code. The director may apply alternative procedures to determine background concentrations if necessary to account for all conditions considered in the TMDL, including, but not limited to, cases where background concentrations vary substantially with flow such that a background concentration derived in accordance with rule 3745-2-05 of the Administrative code may not be appropriate.

(4) The loading capacity for the purpose of establishing a TMDL shall be determined as the largest load of a pollutant that a water body can receive without violating water quality standards at any applicable site within the TMDL implementation plan assessment area (outside of applicable mixing zones). Separate loading capacities may be determined for each flow condition or season applicable to the TMDL. Pollutant loads for sources which only affect the receiving water at certain flow conditions shall be determined to maintain only the loading capacities applicable at those conditions.

(5) Each TMDL shall include a MOS sufficient to account for technical uncertainties in establishing the TMDL. The TMDL implementation plan 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 conservation modeling assumptions to establish WLAs and LAs.

(6) TMDLs may include reserved allocations of loading capacity to accommodate various needs including, but not limited to, future growth, additional sources and environmental reserves. Where adequate 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 this rule and section 6111.563 of the Revised Code to include an allocation for the new or expanded discharge.

(7) Where appropriate and where sufficient data are available, TMDLs shall reflect contributions to the water column from sediments inside and outside of any applicable mixing zones. 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 criteria.

(8) TMDLs shall be based on the assumption that a pollutant does not degrade. However, the director may take into account degradation of the pollutant if each of the following conditions are met:

(9) TMDLs for metals shall be determined based on the total recoverable form of that metal provided by all sources considered in that TMDL. The loading capacity for that TMDL shall be determined to maintain the total recoverable criteria applicable to that metal, with the following exceptions:

(10) TMDLs shall reflect, where appropriate and where sufficient data are available, point source and nonpoint source pollutant loads resulting from wet weather events.

(11) In addition to the requirements of paragraphs (B)(1) to (B)(10) of this rule, the director shall consider and evaluate the factors in divisions (B) and (C) of section 6111.562 of the Revised Code.

(1) For the purpose of establishing a TMDL, LAs shall be based on at least the following information:

(2) For LAs established on the basis of paragraph (C)(1)(c) of this rule, monitoring data 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 implementation plan and to revise the point source allocations and LAs as necessary to ensure that water quality standards will be achieved within the time-period established in the TMDL.

(3) For nonpoint sources considered in a TMDL that may affect the receiving water at stream flows at or below the stream design flows applicable under rule 3745-2-05 of the Administrative Code, LAs established in a TMDL shall be determined in accordance with rule 3745-2-05 of the Administrative Code such that water quality criteria are maintained at the design conditions.

(4) For nonpoint sources considered in a TMDL that only affect the receiving water at stream flows higher than the stream design flows applicable under rule 3745-2-05 of the Administrative Code, LAs may be established using stream flows and procedures that the director determines are appropriate for that nonpoint source and ensure that applicable water quality standards will be maintained whenever that nonpoint source load occurs.

(1) If TMDLs are established in TMDL implementation plans for different segments of the same watershed and include allocations for the same pollutant for the same point source, then WLAs for that pollutant and point source shall be consistent with the most stringent of those allocations.

(2) For point sources considered in a TMDL that discharge at stream flows at or below the stream design flows applicable under rule 3745-2-05 of the Administrative Code, WLAs shall be determined in accordance with rule 3745-2-05 of the Administrative Code such that water quality criteria are maintained at the design conditions.

(3) For point sources considered in a TMDL that only discharge at stream flows higher than the stream design flows applicable under rule 3745-2-05 of the Administrative Code, WLAs may be established using stream flows and procedures that the director determined are appropriate for that point source and ensure that applicable water quality standards will be maintained whenever that point source load occurs.

(4) WLAs determined as part of a TMDL shall be used to determine WQBELs for that discharge in accordance with rule 3745-2-06 of the Administrative Code.

(1) TMDLs shall be established and implemented through a TMDL implementation plan. An implementation plan shall address attainment of applicable water quality standards, determined in accordance with rule 3745-2-04 of the Administrative Code (or as otherwise applicable in accordance with Chapter 3745-1 of the Administrative Code) for each pollutant for which a TMDL is established.

(2) Where an assessment and remediation plan meets the requirements of this rule and the public participation requirements applicable to TMDLs, Ohio EPA may use the assessment and remediation plan in lieu of a TMDL implementation plan. Assessment and remediation plans may include, but are not limited to, the lake Erie lakewide management plan, remedial action plans and water quality management plans. Any part of an assessment and remediation plan that satisfies one or more requirements under Section 303(d) of the act or the act's implementing regulations may be part of a TMDL implementation plan.

(3) A TMDL implementation plan may be based on attaining water quality standards over a period of time, with specific controls on individual sources being implemented in stages. Where implementing a TMDL implementation plan will not immediately attain water quality standards, the TMDL implementation plan shall reflect reasonable assurances that water quality standards will be attained in a reasonable period of time. At a minimum, the following factors shall be considered by Ohio EPA in determining the reasonable period of time in which water quality standards will be met: