SECTION 785:46-15-8. Assessment of Agriculture support

(a)   Scope. The provisions of this Section shall be used to determine whether the beneficial use of Agriculture designated in OAC 785:45 for a waterbody is supported.

(b)   General support tests for chlorides, sulfates and TDS.

(1)   The Agriculture beneficial use designated for a waterbody shall be deemed to be fully supported with respect to chloride if the mean of all chloride sample concentrations from that waterbody do not exceed the yearly mean standard prescribed in Appendix F or site specific criteria promulgated in Appendix E of OAC 785:45 and no more than 10% of the sample concentrations from that waterbody exceed the sample standard prescribed in Appendix F or site specific criteria promulgated in Appendix E of OAC 785:45.

(2)   The Agriculture beneficial use designated for a waterbody shall be deemed to be not supported with respect to chloride if the mean of all chloride sample concentrations from that waterbody exceeds the yearly mean standard prescribed in Appendix F or site specific criteria promulgated in Appendix E of OAC 785:45, or greater than 10% of the sample concentrations from that waterbody exceed the sample standard prescribed in Appendix F or site specific criteria promulgated in Appendix E of OAC 785:45. Provided, if the chloride sample concentrations are each less than 250 mg/L, then the Agriculture beneficial use shall be deemed to be fully supported with respect to chloride.

(3)   The Agriculture beneficial use designated for a waterbody shall be deemed to be fully supported with respect to sulfate if the mean of all sulfate sample concentrations from that waterbody do not exceed the yearly mean standard prescribed in Appendix F or site specific criteria promulgated in Appendix E of OAC 785:45 and no more than 10% of the sample concentrations from that waterbody exceed the sample standard prescribed in Appendix F or site specific criteria promulgated in Appendix E of OAC 785:45.

(4)   The Agriculture beneficial use designated for a waterbody shall be deemed to be not supported with respect to sulfate if the mean of all sulfate sample concentrations from that waterbody exceeds the yearly mean standard prescribed in Appendix F or site specific criteria promulgated in Appendix E of OAC 785:45, or greater than 10% of the sample concentrations from that waterbody exceed the sample standard prescribed in Appendix F or site specific criteria promulgated in Appendix E of OAC 785:45. Provided, if the sulfate sample concentrations are each less than 250 mg/L, then the Agriculture beneficial use shall be deemed to be fully supported with respect to sulfate.

(5)   The Agriculture beneficial use designated for a waterbody shall be deemed to be fully supported with respect to TDS if the mean of all TDS sample concentrations from that waterbody do not exceed the yearly mean standard prescribed in Appendix F or site specific criteria promulgated in Appendix E of OAC 785:45 and no more than 10% of the sample concentrations from that waterbody exceed the sample standard prescribed in Appendix F or site specific criteria promulgated in Appendix E of OAC 785:45.

(6)   The Agriculture beneficial use designated for a waterbody shall be deemed to be not supported with respect to TDS if the mean of all TDS sample concentrations from that waterbody exceeds the yearly mean standard prescribed in Appendix F or site specific criteria promulgated in Appendix E of OAC 785:45, or greater than 10% of the sample concentrations from that waterbody exceed the sample standard prescribed in Appendix F or site specific criteria promulgated in Appendix E of OAC 785:45. Provided, if the TDS sample concentrations are each less than 700 mg/L, then the Agriculture beneficial use shall be deemed to be fully supported with respect to TDS.

(c)   Use of site specific data. If the appropriate state environmental agency determines that the stream segment averages prescribed in Appendix F of OAC 785:45 are not appropriate for the entirety of a given stream segment or there is no value listed in Appendix F or site specific criteria promulgated in Appendix E for the stream segment average for the parameter of concern, then yearly mean standards and sample standards developed from site specific data may be used to assess whether the use of Agriculture is supported for that waterbody.

(d)   Use of data for lakes.

(1)   Lakes with one WBID segment. For support assessment in lakes with a single WBID segment, the segment averaged value prescribed in Appendix F to that same WQM segment shall be used.

(2)   Lakes with multiple WBID segments. For support assessment in lakes with multiple WBID segments, each segment shall use the segment averaged value prescribed in Appendix F to that same WQM segment when available. If a WBID segment in a lake has no corresponding WQM segment data available in Appendix F, the segment averaged value prescribed in Appendix F to the WQM segment immediately downstream of the lake shall be used.

[Source: Added at 17 Ok Reg 1775, eff 7-1-00; Amended at 22 Ok Reg 1607, eff 7-1-05; Amended at 24 Ok Reg 2445, eff 7-1-07; Amended at 25 Ok Reg 1455, eff 7-1-08; Amended at 28 Ok Reg 1017, eff 7-1-11]