Procedures to Implement the Texas Surface Water Quality Standards

Procedures to Implement the Texas Surface Water Quality Standards

Prepared by Water Quality Division

RG-194 June 2010

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Contents

Introduction................................................................................................. 12

Determining Water Quality Uses and Criteria........................................ 14

Classified Waters .......................................................................................................... 14 Unclassified Waters ...................................................................................................... 14 Presumed Aquatic Life Uses......................................................................................... 14

Assigned Aquatic Life Uses...................................................................................... 16

Evaluating Impacts on Water Quality...................................................... 20

General Information...................................................................................................... 20 Minimum and Seasonal Criteria for Dissolved Oxygen ............................................... 21 Federally Endangered and Threatened Species ............................................................ 21

Screening Process ..................................................................................................... 22 Additional Permit Limits .......................................................................................... 22 Edwards Aquifer ....................................................................................................... 23 Bacteria ......................................................................................................................... 24 Recreational Uses and Criteria.................................................................................. 24 Assigning Recreational Uses .................................................................................... 25 Wastewater Permitting.............................................................................................. 26 Nutrients........................................................................................................................ 26 Introduction............................................................................................................... 26 General Screening Approach for Nutrient Impacts .................................................. 26 Nutrient Screening for Main Pool Effects in Reservoirs with Numerical Nutrient Criteria ...................................................................................................................... 30 Nutrient Screening for Local Effects in Reservoirs.................................................. 38 Nutrient Screening for Streams and Rivers .............................................................. 47 Nutrient Screening for Estuaries............................................................................... 53 Other Applicable Rules................................................................................................. 53

Antidegradation .......................................................................................... 55

Policy ............................................................................................................................ 55 General Applicability.................................................................................................... 55 Tier 1--Protecting Uses................................................................................................ 56 Protecting Impaired Waters under Tier 1...................................................................... 57

Definitions................................................................................................................. 57 General Provisions .................................................................................................... 58 Applicability to Specific Parameters ........................................................................ 58 Procedures for Discharges to Listed Water Bodies .................................................. 59 Applicability of Pollution Reduction Programs........................................................ 60 Examples of Permitting to Listed Water Bodies....................................................... 60

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Tier 2--Protecting High-Quality Waters...................................................................... 61 Applicability ............................................................................................................. 61 Evaluating the Potential for Degradation of Water Quality...................................... 63 Examples Where Degradation Is Unlikely to Occur................................................. 65 Examples Where Degradation Is Likely to Occur .................................................... 66 Evaluation of Alternatives and Economic Justification............................................ 66 Agency Review of Degradation................................................................................ 67

Tier 3--Outstanding National Resource Waters .......................................................... 67 Watershed Protection Rules.......................................................................................... 68 Public Notice................................................................................................................. 69

Mixing Zones and Critical Conditions...................................................... 70

General Information...................................................................................................... 70 Mixing Zones and ZIDs for Aquatic Life Protection.................................................... 70 Critical Conditions for Aquatic Life Protection............................................................ 72 Determining the 7Q2..................................................................................................... 75 Determining Critical Low-Flows for Streams and Rivers that are Dominated by Springflow..................................................................................................................... 77 Mixing Zones and Critical Conditions for Human Health Protection .......................... 78 Determining the Harmonic Mean Flow ........................................................................ 80 Diffusers........................................................................................................................ 82

Modeling Dissolved Oxygen....................................................................... 83

General Information...................................................................................................... 83 Model Selection and Inputs .......................................................................................... 83 Screening Level Methods ............................................................................................. 84

Nontidal Streams and Rivers .................................................................................... 84 Tidal Water Bodies, Ponds, and Lakes ..................................................................... 87 Critical Low-Flow Values for East and South Texas Streams ..................................... 88 Regression Equation Relating Dissolved Oxygen, Flow, and Bedslope .................. 91 Calculating Bedslope ................................................................................................ 92 Guidelines for Adjusting the Regression Equation................................................... 92 Regression Equation for Establishing Critical Low-Flows in Specific Water Bodies in the Cypress Creek Basin ....................................................................................... 93 Water Bodies with a Dissolved Oxygen Impairment ................................................... 94

Whole Effluent Toxicity Testing (Biomonitoring)................................. 102

Applicability ............................................................................................................... 102 Chronic and 48-Hour Acute Tests .............................................................................. 104

Test Types............................................................................................................... 104 Test Acceptability Criteria...................................................................................... 105 Statistical Interpretation of Test Results ................................................................. 107 Test Frequencies ..................................................................................................... 108 Dilution Series, Dilution Water, and Type of WET Test ....................................... 110 Reasonable Potential Determination....................................................................... 113

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Toxicity Reduction Evaluations (TREs)................................................................. 115 24-Hour Acute (100% End-of-Pipe) Tests ................................................................. 118

Test Types............................................................................................................... 118 Test Acceptability Criterion.................................................................................... 119 Test Frequencies ..................................................................................................... 119 Toxicity Reduction Evaluations (TREs)................................................................. 119 Toxicity Control Measures ..................................................................................... 121 Test Substitution ......................................................................................................... 122 Toxicity Attributable to Dissolved Salts..................................................................... 122 TDS Exemption--24-Hour Acute (100% End-of-Pipe) Tests ............................... 125 TDS Exemption--Chronic and 48-Hour Acute Tests ............................................ 126 Ammonia Toxicity ...................................................................................................... 128 Controlling Potential Ammonia Toxicity ............................................................... 128 Toxicity Attributable to Ammonia.......................................................................... 129 Toxicity Attributable to Diazinon............................................................................... 129

Toxic Pollutants......................................................................................... 130

General Provisions ...................................................................................................... 130 Specific Numerical Criteria ........................................................................................ 131 Deriving Permit Limits for Aquatic Life Protection................................................... 132

General Approach ................................................................................................... 132 Water Quality Parameters That Affect Aquatic Life Criteria................................. 132 Calculating Effluent Fractions ................................................................................ 133 Calculating Waste Load Allocations ...................................................................... 135 Calculating the Long-Term Average ...................................................................... 136 Calculating Daily Average and Daily Maximum Permit Limits ............................ 137 Deriving Permit Limits for Human Health Protection................................................ 140 General Approach ................................................................................................... 140 Calculating the Effluent Fraction............................................................................ 141 Calculating the Waste Load Allocation .................................................................. 142 Calculating the Long-Term Average and Permit Limits ........................................ 142 Establishing Permit Limits for Toxic Pollutants without Criteria .............................. 143 Aquatic Life Criteria ............................................................................................... 143 Human Health Criteria............................................................................................ 146 Correcting for Background Concentrations ................................................................ 148 Procedure for Developing Permit Limits................................................................ 148 Obtaining Reliable Water Quality Data.................................................................. 152 Once-Through Cooling Water Discharges.................................................................. 153 Applicability ........................................................................................................... 153 Permit Action .......................................................................................................... 153 Statistical Study ...................................................................................................... 154 Source Investigation................................................................................................ 155 Exemption Approval or Denial............................................................................... 155 Collecting Site-Specific Data...................................................................................... 156 Hardness, pH, and Chloride .................................................................................... 156 TSS, Partition Coefficients, and Bioavailable Fractions of Metals ........................ 159 Calculating Permit Limits for Specific Toxic Pollutants............................................ 164

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Calculating Permit Limits for Mercury, PCBs, Dioxins/Furans, DDT, DDD, and DDE ........................................................................................................................ 164 Calculating Permit Limits for Silver....................................................................... 166 Calculating Permit Limits for Chromium ............................................................... 167 Establishing Permit Limits for Toxic Pollutants......................................................... 168 Application Screening............................................................................................. 168 Analytical Procedures and MALs........................................................................... 169 Alternate Test Procedures ....................................................................................... 172 Defining Permit Limits ........................................................................................... 173

Screening Procedures and Permit Limits for Total Dissolved Solids.. 174

Introduction................................................................................................................. 174 Screening Procedures for TDS.................................................................................... 175 Determining Site-Specific Ambient TDS Values ....................................................... 180 Establishing Permit Limits for TDS ........................................................................... 181 Final Evaluation and Additional Considerations for TDS.......................................... 184

TPDES Storm Water Permits.................................................................. 187

General Provisions ...................................................................................................... 187 Reviewing Permit Applications .................................................................................. 187 Site-Specific Information............................................................................................ 189 Antidegradation Review of Storm Water Permits ...................................................... 189 Discharges to Impaired Waters................................................................................... 189 Discharges to the Edwards Aquifer Recharge Zone ................................................... 190 Discharges to Specific Watersheds and Water Quality Areas .................................... 190

Site-Specific Standards and Variances ................................................... 191

General Provisions ...................................................................................................... 191 Interim Permit with a Variance................................................................................... 191 Variance Extensions.................................................................................................... 192 Coordinating with EPA............................................................................................... 193 Temporary Standards .................................................................................................. 194 Site-Specific Standards for Aquatic Life Use............................................................. 195

Aquatic Life UAA Review and Approval .............................................................. 196 Aquatic Life UAAs for Typical Sites ..................................................................... 197 Site Complications Requiring Additional Justification .......................................... 199 Site-Specific Standards for Recreational Use ............................................................. 199 Recreational UAA Review and Approval............................................................... 200 How to Conduct Recreational UAAs...................................................................... 201 Wildlife Sources of Bacteria................................................................................... 202 Site-Specific Numerical Standards for Aquatic Life .................................................. 202 Site-Specific Standards for Total Toxicity ................................................................. 207

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