1 / 10

Changes to §307.8-Application of Standards and §307.9-Determination of Standards Attainment

This overview discusses the application of water quality standards, including flow-dependent criteria and mixing zones. It also provides information on the determination of standards attainment through sampling and analytical procedures.

egomez
Download Presentation

Changes to §307.8-Application of Standards and §307.9-Determination of Standards Attainment

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Changes to §307.8-Application of Standards and §307.9-Determination of Standards Attainment Gregg Easley Water Quality Standards Team Texas Commission on Environmental Quality

  2. 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 • Once-through cooling water discharges • Storm water discharges

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

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

  5. 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)] • Human health toxics criteria [§307.8(a)(8)] • Recreational criteria (geo mean) for perennial streams [§307.8(a)(1)(A) & (F)] • Addressing instances of zero stream flow

  6. Flow-Dependent Applications • Exempting some recreational criteria at high-flow conditions • 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 • considered an NPDES implementation provision and not subject to approval

  7. 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)]

  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

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

  10. 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) • 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

More Related