Oklahoma Administrative Code › Title 252 - Department of Environmental Quality › Chapter 740 - Implementation of Oklahoma's Water Quality Standards › Subchapter 13 - Implementation of Antidegradation Policy › Section 252:740-13-8 - Antidegradation review in surface waters

Current through Vol. 41, No. 20, July 1, 2024
(a)
General.
The antidegradation review process below presents the
				framework to be used when making decisions regarding the intentional lowering
				of water quality, where water quality is better than the minimum necessary to
				protect beneficial uses. OWRB technical guidance TRWQ2017-01 provides
				additional information.
(b)
Determination of Assimilative Capacity in Tier 2, Tier 2.5, and Tier 3
				Waters.
(1) All water quality
				monitoring and technical analyses necessary to determine receiving waterbody
				assimilative capacity for all applicable numeric and narrative criteria and
				associated parameters protective of waterbody beneficial uses shall be
				conducted by the interested party.
(2) Prior to initiating any monitoring or
				technical analysis to support determination of waterbody assimilative capacity,
				the interested party shall submit a workplan for review and approval by DEQ
				staff.
(3) As part of an approved
				workplan, the interested party shall characterize existing water quality of the
				receiving waterbody for each applicable criteria and associated parameters and
				evaluate if there is available assimilative capacity. Characterization of
				existing water quality shall address, at a minimum:
(A) Measurement of load and or concentration
				for all applicable criteria and associated parameter(s) in the receiving water;
				and
(B) The measurement of both
				existing and proposed point and nonpoint source discharge concentrations and or
				loadings; and
(C) The critical low
				flow or critical lake level of the receiving waterbody, including drought of
				record in waterbodies receiving IPR discharges; and
(D) The limnological, hydrologic, seasonal,
				spatial and temporal variability and critical conditions of the waterbody;
				and
(E) Volumetric determination of
				anoxic dissolved oxygen condition consistent with OAC 252:730 and OAC 252:740;
				and
(F) The bioaccumulative nature
				of a pollutant shall be considered when determining assimilative capacity;
				and
(G) The 303(d) list as
				contained in the most recently approved Integrated Water Quality Assessment
				Report shall be reviewed and any difference between the water quality
				assessment information and the characterization of existing water quality shall
				be reconciled.
(4)
				Assimilative capacity shall be determined by comparing existing water quality,
				as determined consistent with subsection (a)(3) above to the applicable
				narrative and numeric criteria. In Tier 2 waters, assimilative capacity shall
				be determined and used with a margin(s) of safety (OAC
				252:740-13-8(d)(1)(D)),
				which takes into account any uncertainty between existing or proposed
				discharges and impacts on receiving water quality.
(5) When existing water quality does not meet
				the criterion or associated parameter necessary to support beneficial use(s) or
				is identified as impaired on Oklahoma's 303(d) list as contained in the most
				recently approved Integrated Water Quality Assessment Report, no assimilative
				capacity shall exist for the given criterion.