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Vicki Conway January 19, 2005

Are Current “Adaptive” TMDLs Really Adaptive?. Vicki Conway January 19, 2005. SANITATION DISTRICTS OF LOS ANGELES COUNTY. Adaptive TMDLs…NOT. 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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Vicki Conway January 19, 2005

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  1. Are Current “Adaptive” TMDLs Really Adaptive? Vicki Conway January 19, 2005 SANITATION DISTRICTS OF LOS ANGELES COUNTY

  2. Adaptive TMDLs…NOT If it looks like a duck and quacks like a duck, it may not always be an adaptive duck in the TMDL world.

  3. 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.”

  4. 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

  5. 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

  7. 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)

  8. 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)

  9. 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

  10. 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 POTW’s

  11. Why These Are Not Truly Adaptive… • Lack of Political Will to Revise WLA’s 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.

  12. 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

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