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Response to Comments on T ive WDRs -2 - 16 March 2009 Harney Lane Landfill San Joaquin County y toluene were also detected above trace concentrations in two of the monitoring events during 2008 (First and Third Quarters) and no demonstration of laboratory contamination was made for these VOCs. As such, we cannot agree that Long term monitoring data at the site clearly shows declining concentrations for all of the detected VOCs at this time. On the other hand, we agree that declining concentrations of VOCs in groundwater at the site have generally coincided with improvements in the LFG extraction system. We plan to revise Finding 31 of the tentative WDRs to read as follows: Historical monitoring data for the site generally indicates declining concentrations of VOCs coincident with improvements to the LFG extraction system. Since 2007, the primary VOCs historically.detected in groundwater at the site (e.g., PCE, Freon 12, and 9,2 Dichloropropane)have ,been detected at trace or non-detect levels. There will be no changes to or re-issuance of the tentative WDRs cover letter. 23 February 2009 letter 2. Discrete Retest Protocol (Monitoring Specification 22b) a. Excerpt From Comment Our concern is the requirement that if either of the two retests samples report the VOC of concern then Evaluation Monitoring is triggered, resulting in great expense to the County for what may be a false positive. This concern is based on the historical data showing that-common laboratory contaminants contribute to the first test, and knowing that they could also be found in one of the two retest samples. . . I suggest. . .- this Specification be reworded to reflect that: If it is present in the groundwater, then it will be detected in both samples. If a compound is not in the groundwater, then it will not be detected in either sample unless laboratory contamination has occurred again. If it is found in one but not both samples, then it is probable that laboratory contamination has occurred again, and the result is therefore inconclusive. In such a case, we would be allowed to retest again until the results are conclusive. b. Response — It is unlikely that a sporadically detected VOC would itself trigger further evaluation monitoring. Also, given that there is an existing release.at the site, detection of an additional VOC would merely result in that VOC being added to the monitoring parameter list (if not already on it) per Monitoring Specification 24. Monitoring Specification 23 allows the Discharger to make the appropriate demonstration under,Title 27 to show that a particular exceedance is the result of an outside factor such as laboratory interferences. Absent such demonstration, it is possible, if not likely, that such sporadically VOCs are from LFG. This is one reason why the MRP requires monitoring LFG for VOCs. No change to WDRs warranted. 3. Background Monitoring Wells (Findings 34 and 35; Provision 5) a. Excerpt From Comment