Vicki Conway

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Are Current Adaptive TMDLs Really Adaptive?

• Vicki Conway
• January 19, 2005

SANITATION DISTRICTS OF LOS ANGELES COUNTY
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Adaptive TMDLsNOT

• If it looks like a duck and quacks like a duck,
  it may not always be an adaptive duck in the TMDL
  world.

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NRC Definition of Adaptive Implementation of
TMDLs

• It is a process of taking actions of limited
  scope commensurate with available data and
  information to continuously improve our
  understanding of a problem and its solutions,
  while at the same time making progress toward
  attaining a water quality standard.

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At First Glance

• Many LARWQCB (Region 4) TMDLs appear to be
  adaptive
• Implementation plans include
• Special scientific studies
• Reopeners - Regional Board considers a Basin
  Plan Amendment for site-specific objectives or
  reconsiders WLA for specific constituents based
  on studies

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At First Glance

• Features that are not adaptive
• MOS explicit margin of safety of 10 percent and
  an additional implicit margin of safety is
  incorporated through conservative model
  assumptions and statistical analysis.
• Seasonal variations and critical conditions are
  prescriptive regardless of basis of WQO.

6
Case Study Upper Santa Clara River Chloride
TMDL

• Objective of 100 mg/L scientifically questionable
• Based on antidegradation
• Coincidentally represents lowest chloride level
  of UC Coop Extension guidelines for irrigation
  water for salt sensitive crops (via leaf
  exposure)
• Historical variations in surface water and
  groundwater quality
• Seasonal variations related to droughts and
  changes in water supply
• Existing use questionable
• Approx. 35 acres avocado crops grown
• No evidence of impacts on agriculture

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Adaptive Elements in the Upper SCR Chloride TMDL
- Studies

• Chloride Source Identification/Reduction,
  Pollution Prevention and Public Outreach Plan
• Groundwater/Surface Water Interaction Model (Year
  2 of 13)
• Evaluation of Appropriate Chloride Threshold for
  the Protection of Sensitive Agriculture (Year 3
  of 13)
• Evaluation of Appropriate Chloride Threshold for
  Endangered Species Protection (Year 3 of 13)
• Development of Site Specific Objectives for
  Chloride (including an ADA) (Year 4 of 13)

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Adaptive Elements in the Upper SCR Chloride TMDL
- Reopeners

• Re-evaluate schedule for agricultural chloride
  threshold study (Year 1 of 13)
• Reconsideration of action taken on final WLA
  (Year 5 of 13)
• Re-evaluation of Schedule to implement Chloride
  Control Measures (Year 9 of 13)

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Why These Are Not Truly Adaptive

• Science is being driven by the schedule
• May result in a higher level of uncertainty, and
  therefore a larger MOS
• Agricultural studies
• Literature review vs. Lab studies vs. Field
  studies
• Osmotic effects vs. Ion Specific Effects
• Groundwater/Surface Water Interaction Model
• Public Domain vs. Proprietary Software-
  constrained to use certain models
• Aquatic life studies
• Testing/evaluating surrogates of ES

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Why These Are Not Truly Adaptive

• No potential for feedback based on actions taken
  to reduce chloride loads
• Self Regenerating Water Softeners (SRWS) will
  reach the end of their service life and chloride
  levels will then decrease
• Due to prohibition of installation of new SRWS,
  population growth will result in lower chloride
  levels from POTWs

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Why These Are Not Truly Adaptive

• Lack of Political Will to Revise WLAs and/or
  Water Quality Objectives
• No relaxation of water quality standards,
  regardless of what the science is telling you
• In 2000, two attempts to revise the Chloride WQO
  failed
• First draft of the SCR Chloride TMDL was proposed
  in 2002. Since then there has been several
  versions, several remands, and a settlement
  agreement
• TMDL is expected to become effective in the near
  future.

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Consequence of Upper SCR Chloride TMDL

• Requires expenditure of millions of dollars to
  conduct all special studies in parallel
• Final WLA are included in TMDL likely difficult
  to change and will be applied as end-of-pipe
  limits
• May result in having to design, construct and
  operate advanced treatment systems prior to
  scientific questions regarding chloride threshold
  being answered
• Only time will tell whether or not the TMDLs are
  truly adaptive