Statutes, codes, and regulations
Oklahoma Administrative Code
Title 252 - DEPARTMENT OF ENVIRONMENTAL QUALITYChapter 740 - IMPLEMENTATION OF OKLAHOMA'S WATER QUALITY STANDARDS
Subchapter 9 - Implementation of Criteria to Protect the Agriculture Beneficial Use
Section 252:740-9-4 - Reasonable potential

Okla. Admin. Code § 252:740-9-4

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Current through Vol. 42, No. 8, January 2, 2025
Section 252:740-9-4 - Reasonable potential
(a)General. The need for a permit limit will be determined on a mineral constituent basis, after application of the reasonable potential equation specified in (b) of this Section, which considers assimilation capacity of the receiving water and effluent variability.
(b)Reasonable potential equation. OAC 252:730-5-13(d) requires that complete mixing of effluent and receiving water be taken into account in the reasonable potential equation. The use of mass balance to obtain wasteload allocations for complete mixing is codified at OAC 252:740-7-3(a). Therefore, the reasonable potential equation for mineral constituents is C = (Qu CB + QeC95) / (Qu + Qe), where C95 = 2.13 Cmean, where Cmean is the geometric mean of all effluent concentrations analyzed for the mineral. If the geometric mean cannot be determined, an arithmetic mean may be used. If sufficient effluent concentration observations exist as determined by the permitting authority, then the permitting authority may compute the 95th percentile concentration and use it as C95, in accordance with OAC 252:740-5-3(b)(1).
(c)Reasonable potential to exceed yearly mean standard. Qu = A and Qe = Qel in OAC 252:740-9-4(b) to obtain a long-term average concentration in-stream after complete mixing. If C is greater than the higher of the YMS or 700 mg/L for TDS or 250 mg/L for chlorides and sulfates, there is a reasonable potential to exceed an Agriculture beneficial use criterion, and a permit limit is required.
(d)Reasonable potential to exceed sample standard. Qu =0.68A and Qe = Qes in OAC 252:740-9-4(b) to obtain a shortterm average concentration in-stream after complete mixing. If C is greater than the higher of the SS or 700 mg/L for TDS or 250 mg/L for chlorides and sulfates, there is a reasonable potential to exceed an Agriculture beneficial use criterion, so a permit limit is required.

Okla. Admin. Code § 252:740-9-4

Adopted by Oklahoma Register, Volume 40, Issue 6, December 1, 2022, eff. 10/25/2022
Adopted by Oklahoma Register, Volume 40, Issue 24, September 1, 2023, eff. 9/15/2023
Amended by Oklahoma Register, Volume 41, Issue 23, August 15, 2024, eff. 9/15/2024