Task 3 Milestone: Approaches for the Recognition and Management of Sensitive Features in the Edwards Aquifer Recharge Zones

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During the past 3 months, I have been observing in the field how the TNRCC Geologic Assessment of sensitive features in the Edwards recharge zone is done by geologists and TNRCC staff. I have also reviewed karst literature, interviewed experts, and abstracted information relevant to the Geologic Assessment. This milestone describes the options for changing the assessment that I have collected and my recommendations on these options for consideration by TNRCC staff.

The major proposed changes are:

  1. Eliminate the category "possibly sensitive" and rank most active karst features as sensitive.
  2. Keep a simple additive assessment and simplify it to include only three variables: classification by feature type, orientation with respect to structure, and a field-based assessment of relative infiltration rate.
  3. Increase emphasis on matching appropriate engineering responses to sensitive features.
  4. Evaluate features encountered during sewer construction to identify those where flow should be maintained.
  5. Improve training by increasing the guidance provided in the instructions.
  6. Reduce variability in assessment by better defining the criteria on which to evaluate relative infiltration rate.
  7. Consider the requirements of other regulatory agencies on developers to reduce confusion and increase compliance.

I recommend that current practices of managing excavation to explore features, and not requiring cave mapping, be retained as they are currently done during assessments. A number of logistical changes are suggested to the instructions and the table. In addition, I propose the following minor changes for consideration: require location of features with GPS and consider improving training by voluntary stakeholder field training days.

After discussion with TNRCC staff, the Instructions to Geologists and Geologic Assessment Table will be revised to include the selected changes.


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