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EPA Comments on the Proposed Decision Logic for Extraction Well Shutdown, DDJC-Sharpe and DDJC-Tracy, October 2003 GENERAL COMMENT 1. The proposed decision logic is incomplete because the criteria for some decisions are not defined. For example, one of the decision diamonds on Figure 1 is, "Is the well capturing an adequate plume fraction?" but there is no definition of"adequate plume fraction." Please provide objective criteria for evaluation of each decision and define terminology used in the decision tree. SPECIFIC COMMENTS 1. Rebound Wells, Page 2: The last sentence indicates that if concentrations are fluctuating around the aquifer cleanup level (ACL), quarterly sampling may be extended to seven quarters, but this decision is not reflected in the decision tree (Figure 1). On Figure 1, the decision that leads to an additional three quarters of monitoring is "Was concentration of last sample greater than 1.2 x ACL?" Please revise the decision tree to include concentrations fluctuating around the ACL as a decision that leads to an additional three quarters of monitoring. 2. Figure 1: The line at the bottom and along the left side of the figure does not have a direction arrow, so it is unclear what should be done when the line is reached. Please provide arrows to indicate whether the decision process returns to "Start" or to another exit point. 3. Figure 1: It is unclear whether plume capture is included in the cost/benefit evaluation of "continued pumping of an existing well compared to well shutdown and alternative actions and their consequences." Please define the scope of this evaluation and include plume capture as part of the scope. In addition,please provide a discussion in text of what some of the alternative actions might be. 4. Figure 1: The logic leading to implementing an alternative action is unclear, and the meaning of"lowest cost/benefit option" is unclear. The question, "Is shutdown the lowest 1