1. Potential Changes to Sections 307.8 and 307.9: Standards Applicability and Attainment Gregg Easley TCEQ Water Quality Standards Team September 6, 2007

2. Flow-Dependent Applications Remove low-flow exemptions for the following criteria (perennial streams): –dissolved solids for classified streams –human health toxics (currently exempted below harmonic mean) –recreational criteria (geo mean) for all perennial streams –exemptions resume below some negligible flow value (e.g., 0.1 CFS)

3. Flow-Dependent Applications (continued) What about intermittent streams with perennial pools? –currently no exemption specified to address very dry conditions –exempting criteria when stream flow ceases –could use pool coverage threshold (e.g., 50%); assessment guidance uses 20% –other methods to define drying, stagnant pools?

4. Applicable Low-Flow Criteria Propose alternative to 7Q2 for larger spring-fed systems –Barton Springs, Upper Blanco River, Comal River, Medina River, Upper San Marcos River –alternative values to be presented at future workgroup meeting (with IP revisions) –language to be added to 307.8 describing how values derived and where they reside –Values could be lower where unique biological assemblages present

5. Table of Segment-Specific Low Flow Criteria (Appendix B) Move Appendix B to the standards implementation procedures Remove Appendix B related provisions in 307.8 Alternative low-flow values for spring-fed systems to be included in relocated table

6. Standards Attainment Topics Representative Samples –point to guidance on spatial and temporal “representativeness” found in SWQM procedures and assessment guidance documents –work with SWQM staff in their concurrent revisions of the assessment guidance –additional language in the standards?

7. Standards Attainment Topics (continued) Collection of water samples –bacteria and temperature determinations based on surface samples –dissolved solids and pH apply to mixed surface layer, but surface samples adequate –dissolved oxygen samples currently require vertical profile of mixed surface layer proposed change to allow for surface samples

8. Standards Attainment Topics (continued) Sampling periodicity and evaluation –designation of appropriate averaging statistic dissolved solids and human health criteria will be estimated by the median, rather than the arithmetic mean recreational standards attainment to be based on geometric mean criteria; single sample maximum for swimmer notification and wastewater permits –consideration of averaging period or allowable frequency of exceedance for other parameters

9. Standards Attainment Topics (continued) Natural background conditions –is language needed to ensure such conditions accounted for when applying the standards? –example from Florida’s water quality standards –similar provision could be placed in 307.9 or other areas as appropriate –are existing, abbreviated statements in the general and site-specific criteria sections of the Texas standards