Changes to § Application of Standards and §307.9-Determination of Standards Attainment Gregg Easley Water Quality Standards Team Texas Commission on Environmental Quality

Overview of §307.8 – Application of Standards Sets forth conditions under which portions of the standards do not apply:  Low-flow conditions (FW streams/rivers)  Mixing zones (permitted surface water discharges)  Other Minimum analytical levels Minimum analytical levels Once-through cooling water discharges Once-through cooling water discharges Storm water discharges Storm water discharges

Flow-Dependent Applications of Standards in Streams §307.8(a)

Flow-Dependent Applications  Low-flow statistics for spring-fed and non- spring-fed systems 7Q2 still used for non-spring-fed systems 7Q2 still used for non-spring-fed systems Alternative statistic for ~6 large spring systems Alternative statistic for ~6 large spring systems Flow probability approach (e.g. San Marcos River)Flow probability approach (e.g. San Marcos River) Or, direct percentile rank (e.g., 10 th percentile)Or, direct percentile rank (e.g., 10 th percentile) Lower value could apply where unique biological assemblages present Lower value could apply where unique biological assemblages present

Flow-Dependent Applications  Revision of low-flow exemptions for criteria expressed as long-term averages [§307.8(a)(1)] Dissolved solids for classified streams in Appendix A [§307.8(a)(1)(A)] Dissolved solids for classified streams in Appendix A [§307.8(a)(1)(A)] Human health toxics criteria [§307.8(a)(8)] Human health toxics criteria [§307.8(a)(8)] Recreational criteria (geo mean) for perennial streams [§307.8(a)(1)(A) & (F)] Recreational criteria (geo mean) for perennial streams [§307.8(a)(1)(A) & (F)] Addressing instances of zero stream flow Addressing instances of zero stream flow

Flow-Dependent Applications  Exempting some recreational criteria at high-flow conditions proposed for 2000 Standards, but not adopted proposed for 2000 Standards, but not adopted  Other options/suggestions for flow applicability and critical conditions  Removal of Appendix B references proposal to move Appendix B to IP’s proposal to move Appendix B to IP’s considered an NPDES implementation provision and not subject to approval considered an NPDES implementation provision and not subject to approval

Mixing Zones [§307.8(b)] – Discussion of EPA Comments  specifying size limits for mixing zones  applying standards to point of discharge in cases of low-dilution receiving waters [§307.8(b)(4)]  preventing mixing zone overlap with zone of influence of public drinking water supply wells [similar to §307.8(b)(8)]

Overview of §307.9 – Determination of Standards Attainment Describes sampling and analytical procedures to determine standards attainment:  General sampling and assessment procedures references  representative samples  sample collection and preservation  sample analysis  sampling periodicity and evaluation  biological integrity  additional parameters

Representative Sampling [§307.9(a) – (c)]  expand on how samples for standards compliance are representative consider storm flow exclusion consider storm flow exclusion better define peripheral areas that might not be considered representative better define peripheral areas that might not be considered representative evaluate spatial averaging for certain parameters, as is done for dissolved solids evaluate spatial averaging for certain parameters, as is done for dissolved solids  evaluate vertical averaging for samples, mixed surface layer for DO

Sampling Periodicity and Evaluation [§307.9(e)]  reevaluate the appropriate averaging statistic (mean or median) and averaging period for a given criterion bacteria – assess standards attainment with geo mean criterion only (use single sample maximum for swimmer safety notification and wastewater permit evaluation) bacteria – assess standards attainment with geo mean criterion only (use single sample maximum for swimmer safety notification and wastewater permit evaluation) chloride, sulfate, total dissolved solids, and human health toxics criteria currently are evaluated with samples averaged (arithmetic mean) over a period of at least one year chloride, sulfate, total dissolved solids, and human health toxics criteria currently are evaluated with samples averaged (arithmetic mean) over a period of at least one year  additional considerations/suggestions on identifying impaired water bodies