Procedures to Implement the Texas Surface Water Quality Standards Peter Schaefer Standards Implementation Team 512-239-4372 peter.schaefer@tceq.texas.gov The primary contact for the Procedures to Implement the Texas Surface Water Quality Standards is Mr. Peter Schaefer, Team Leader of the Standards Implementation Team.

What are “Implementation Procedures (IPs)” Procedures to Implement the Texas Surface Water Quality Standards (IPs) RG-194 A guidance document that explains how TCEQ applies the Texas Surface Water Quality Standards The Procedures to Implement the Texas Surface Water Quality Standards (IPs) are a regulatory guidance document explaining how the Texas Surface Water Quality Standards are implemented within Texas Pollutant Discharge Elimination System Permits. They cover a broad range of water quality permitting topics such as antidegradation, dissolved oxygen modeling, how to translate water quality criteria into permit limitations, procedures for calculating site specific criteria including TDS, chloride and sulfate, and how to request a variance from a water quality standard…and more.

Main Topics Covered in IPs Determining Water Quality Uses and Criteria Evaluating Impacts to Water Quality Antidegradation Mixing Zones and Critical Conditions Dissolved Oxygen Modeling (Continued on next slide) Slide showing main topics covered in document

Main Topics Covered in IPs (cont.) Biomonitoring (WET) Toxic Pollutants TDS Screening Procedures Stormwater Permits Variance and Site-Specific Standard Appendices Other Slide showing main topics covered in document

Determining Water Quality Uses and Criteria Classified Waters Unclassified Water Presumed Aquatic Life Uses

Evaluating Impacts on Water Quality Endangered and Threatened Species Edwards Aquifer Bacteria Nutrient Screening The following are topics proposed to be addressed in the 2018 IP Revision process. The revision process will involve stakeholder input and opportunity for public comment. Procedures for Reasonable Potential Analysis for whole effluent toxicity testing will be revised in the IPs. Updates to dechlorination requirements for minor municipal discharges. Variance procedures Thermal Evaluation Strategy for permits with temperature limits higher than segment criteria. Updates to critical low-flow (7Q2) and harmonic mean (HM) flow data for classified segments. Updates to classified segment ambient water quality values. Supporting information for 316(b) rule implementation. Updates to federally listed threatened and endangered species. Updates to Minimum Analytical Levels (MALs). pH screening procedures for certain entities that discharge directly to a classified segment. Correcting errors/omissions in current IPs.

Antidegradation Tier 1 Tier 2 Watershed Protection Rules

Mixing Zones and Critical Conditions MZ and ZIDs Critical Conditions Determining 7Q2 and HM Human Health Diffusers

Dissolved Oxygen Modeling Model Selection and Inputs Screening Level Methods Critical Low Flow Values for East and South Texas Streams DO Impairments

Biomonitoring (WET) Chronic and 48 Hour Acute Tests 24 Hour Acute Test Substitution Toxicity Attributable to TDS Ammonia Toxicity

TDS Screening Procedures Flow Status Determining Site-Specific Ambient TDS Values Establishing TDS Permit Limits Final Evaluation and Considerations

Stormwater Permits Site-Specific Conditions Antidegradation Review of Stormwater Permit Discharges to Impaired Waters Discharges to Edwards Aquifer Recharge Zone Watershed Rules

Site-Specific Standards and Variances Interim Permit with Variance Variance Extension Site-Specific Standards EPA Coordination Standards Revision

Appendices Playa Lake Policy Endangered and Threatened Species Critical Low-Flow Values Segment-Specific Water Quality Values TSS, pH, Hardness, TDS MALs Nutrient Screening Parameters-Reservoirs Flow data from available USGS gaging stations are analyzed based on the latest 29 years of data. Both critical low flow data, also called 7Q2 flow, and harmonic mean flow data are calculated for Classified Segments. The 7Q2 is defined in the Standards as “the lowest average stream flow for seven consecutive days with a recurrence interval of two years, as statistically determined from historical data.” Effluent limits in TPDES wastewater discharge permits are designed to maintain the applicable numerical water quality standards for the protection of aquatic life when instream flows are at or above the 7Q2. Harmonic mean (HM) flow is defined in the Standards as “a measure of mean flow in a water course that is calculated by summing the reciprocals of the individual flow measurements, dividing this sum by the number of measurements, and then calculating the reciprocal of the resulting number.” USGS gage data is provisional until data is verified and final data is released.

Any Questions ??? Contact Information Peter Schaefer Peter.schaefer@tceq.texas.gov 512-239-4372 Picture – Bullhide Creek in McClennan County taken during an RWA performed in June 2007.