Transcript Slide 1
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 sitespecific 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 technologybased 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:
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