Water Quality Standards and MS4 Storm Water Permitting

What “standards”? Promulgated as Title 30 of the TAC, Chapter 307 Establishes instream goals for water quality statewide Revised every three years (in theory) EPA approval required All TPDES permits must comply with these water quality standards (WQS) Companion guide RG-194

Basic types of Traditional Standards Narrative –Ex: taste and odor in drinking water Numerical –Ex: toxic substances Site-specific standards –Uses such as aquatic life –Criteria such as fecal coliform –Water bodies with individually listed site- specific standards = classified segment

Antidegradation Tier 1 – Water quality sufficient to protect existing uses will be maintained Tier 2 – Activities subject to regulatory action will not degradation to waters that exceed fishable/swimmable quality All individual and general permits (including storm water) are subject to the antidegradation policy

How do WQS apply to traditional discharge permits? Water bodies that receive a wastewater discharge are reviewed for: –Applicable standards –Determine instream dilution –Set allowable mixing zones

How do WQS apply to traditional discharge permits continued.. Effluent analysis review Permit limits/monitoring requirements DMR

Making the Round Peg fit into the Square Hole Traditional permitting tools are lacking for storm water dischargers: –Not dealing with dry weather conditions –Storm water discharges are not constant or consistent

Making the Round Peg fit into the Square Hole Continued.. –There is no simple way to gather “effluent” data at outfall –Basis for numerical criteria –Existing monitoring data only reflects ambient conditions

Other Challenges… –Lack of state and federal policy –Instream dilution and pollutant loading are time variable –Costs and attainability of WQS are difficult to assess

So How are WQS Applied to Wet Weather Dischargers? It’s pretty obvious that the square peg won’t fit in the round hole. We must take a different approach.

Changes to the WQS and IPs in 2000 Revisions 307.8(e) was added to the WQS: –Storm water quality - BMPs and technology- based limits –Instream monitoring –Specific conditions or limits can be added when warranted –Outfall monitoring where little to no data exists

Special Circumstances Cases where a storm water facility may be reviewed like a wastewater discharge: Retaining water and discharging during dry weather Storm water commingled with wastewater

Discharges to Impaired Water and Other Sensitive Areas Discharges can not cause or contribute to an impairment Edwards Aquifer Rules - 30 TAC, Chapter 213 Watershed Protection Rules 30 TAC, Chapter 311

More Information… Texas Surface Water Quality Standards webpage: Implementation Procedures pubs/pubs/rg/rg-194.html