# Ohio Admin. Code 3745-2-11: Rule 3745-2-11. Dissolved oxygen modeling > Ohio · Regulations · In force URL: https://www.frixlaw.com/law-library/statutes/STATE_OH_ADC_3745_2_11 ## Section - **Citation:** Ohio Admin. Code 3745-2-11 - **Heading:** Rule 3745-2-11. Dissolved oxygen modeling - **Jurisdiction:** Ohio - **Kind:** Regulations - **Status:** In force - **Text as of:** August 14, 2026 - **Source:** Compiled text - **Location:** Ohio Administrative Code / Agency 3745 / Chapter 3745-2 / Rule 3745-2-11 ## Text 119.03 (A) The loading capacity of a flowing receiving water for dissolved oxygen (D.O.) shall be determined by the use of mathematical water quality models. The models may range from simple solutions based on the Streeter-Phelps equation to complex, time variable models. The model complexity required shall be based on site-specific considerations. Whenever possible, these models should be calibrated and verified using site-specific data. (1) Alternative modeling methods including, but not limited to, continuous simulation or probabilistic analyses may be used if the director determines that they are appropriate and protective of water quality criteria. (2) If the director does not have sufficient site-specific stream data for D.O., the director may conduct a wasteload allocation (WLA) to maintain the criteria for ammonia toxicity. The required effluent ammonia may then be used to make a decision regarding necessary treatment related to overall D.O. impact in the receiving water, based on available information on wastewater treatment processes. (B) The following stream design flows shall be used for dissolved oxygen modeling. (1) May to November: 7Q10 for summer. (2) December to February: 7Q10 for winter. (3) The director may determine design flows for streams that are impacted by reservoirs or other physical alterations by taking into account relevant site-specific factors. Stream design flows for such impacted stream segments shall be established to assure protection of designated uses. (4) Alternative flows or seasons may be used if the director determines that the flow or season is as protective as those listed in paragraph (B) of this rule. (C) The background concentration of D.O. shall be based on the percentages of D.O. saturation in this paragraph at the temperature that represents the stream after mixing with the effluent. Site-specific D.O. values may be used if sufficient supporting data are available s may be used if the director determines that the flow or season is as protective as those listed in paragraph (B) of this rule. (C) The background concentration of D.O. shall be based on the percentages of D.O. saturation in this paragraph at the temperature that represents the stream after mixing with the effluent. Site-specific D.O. values may be used if sufficient supporting data are available. (1) Ninety per cent of saturation shall be used for streams classified as exceptional warmwater or coldwater habitat. (2) Eighty per cent of saturation shall be used for all other stream uses. (D) Exception for direct discharges to lake Erie. If it is necessary to determine a WLA for a direct discharge to lake Erie, the mixing assumptions contained in paragraph (B) of rule 3745-2-05 of the Administrative Code shall be used. (E) Exception for direct discharges to the Ohio river. If it is necessary to determine a WLA for a direct discharge to the Ohio river, the mixing assumptions contained in paragraph (A)(2)(f) of rule 3745-2-05 of the Administrative Code shall be used. (F) Multiple discharges. When the director determines that it is necessary to consider multiple discharges in a WLA, the loading capacity may be distributed among discharges using a method deemed appropriate by the director, based on site-specific considerations. This WLA shall be developed pursuant to rule 3745-2-05 of the Administrative Code. Last updated June 25, 2025 at 6:14 PM Supplemental Information Authorized By: 6111.03 , 6111.12 Amplifies: 6111.12 2/24/2024 ## Nearby sections - [Ohio Admin. Code 3745-2-01 Rule 3745-2-01. Purpose and applicability](https://www.frixlaw.com/law-library/statutes/STATE_OH_ADC_3745_2_01.md) - [Ohio Admin. Code 3745-2-02 Rule 3745-2-02. Definitions](https://www.frixlaw.com/law-library/statutes/STATE_OH_ADC_3745_2_02.md) - [Ohio Admin. Code 3745-2-03 Rule 3745-2-03. Application of biological survey data to development of water quality-based effluent limitations](https://www.frixlaw.com/law-library/statutes/STATE_OH_ADC_3745_2_03.md) - [Ohio Admin. Code 3745-2-04 Rule 3745-2-04. Determinations preliminary to development of water quality-based effluent limitations](https://www.frixlaw.com/law-library/statutes/STATE_OH_ADC_3745_2_04.md) - [Ohio Admin. Code 3745-2-05 Rule 3745-2-05. Calculating wasteload allocations](https://www.frixlaw.com/law-library/statutes/STATE_OH_ADC_3745_2_05.md) - [Ohio Admin. Code 3745-2-06 Rule 3745-2-06. Application of preliminary effluent limitations](https://www.frixlaw.com/law-library/statutes/STATE_OH_ADC_3745_2_06.md) - [Ohio Admin. Code 3745-2-07 Rule 3745-2-07. Additive effects of pollutants](https://www.frixlaw.com/law-library/statutes/STATE_OH_ADC_3745_2_07.md) - [Ohio Admin. Code 3745-2-09 Rule 3745-2-09. Whole effluent toxicity provisions and water quality based effluent limit calculation procedures](https://www.frixlaw.com/law-library/statutes/STATE_OH_ADC_3745_2_09.md) - [Ohio Admin. Code 3745-2-10 Rule 3745-2-10. Wasteload allocation for ammonia-nitrogen toxicity](https://www.frixlaw.com/law-library/statutes/STATE_OH_ADC_3745_2_10.md) - [Ohio Admin. Code 3745-2-11 Rule 3745-2-11. Dissolved oxygen modeling](https://www.frixlaw.com/law-library/statutes/STATE_OH_ADC_3745_2_11.md) - [Ohio Admin. Code 3745-2-12 Rule 3745-2-12. Total maximum daily loads](https://www.frixlaw.com/law-library/statutes/STATE_OH_ADC_3745_2_12.md) --- Source: Frix Law Library, https://www.frixlaw.com/law-library/statutes/STATE_OH_ADC_3745_2_11. Check the current official text before relying on it. Not legal advice.