water quality standards and ms4 storm water permitting
TRANSCRIPT
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Water Quality Standards and MS4 Storm Water Permitting
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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
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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
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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
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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
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How do WQS apply to traditional discharge permits continued..
• Effluent analysis review
• Permit limits/monitoring requirements
• DMR
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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
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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
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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
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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.
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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
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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
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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
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More Information…
• Texas Surface Water Quality
Standards webpage: http://www.tceq.state.tx.us/nav/eq/eq_swqs.html
• Implementation Procedures
http://www.tceq.state.tx.us/comm_exec/forms_
pubs/pubs/rg/rg-194.html