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• Adrienne Ellsaesser [EH] From: Meeks, Steven @Waterboards <Steven.Meeks@waterboards.ca.gov> Sent: Monday, January 05, 2015 3:50 PM To: Adrienne Ellsaesser [EH] Subject: RE: Local Voluntary Cleanup Oversight Program Hi Adrienne, We have no problems with San Joaquin County taking the lead on this site; however, we do have some comments/concerns with the existing PCE data or lack of PCE data regarding the former dry cleaner site. Here are some of the concerns with the preliminary assessment report you have provided: 1. Understanding that 131-W through 133-W groundwater samples were part of a previous sample event in 2013, it would have been very helpful to include the analytical data report for these samples in this report for comparison and QA/QC checks. Only 137-W analytical results were provided. Given that 133-W was the sample with the highest TPHg value and resided inside the foot-print of the former dry cleaners (PCE concerns), it would be helpful to look at the reports for any QA/QC issues. Is there a previous assessment report that contains the 131-W through 133-W analytical lab reports?These should be looked at and verified. 2. Even if the groundwater PCE concentrations were non-detect,Table 2 should have included them since they are a chemical of concern. One would expect that if an EPA 8260 were run,that PCE would have been included if found; however, I can't verify this because the lab report was not included. This should be confirmed by looking at the lab report. 3. PCE vapor samples did show low PCE, however,the IPS tracer compound was detected at high enough concentrations to warranty repeat sampling and possibly depth discrete samples. We would require additional sampling to confirm the low PCE concentrations due to the tracer gas leak. Five-foot sample depths would be more appropriate to us. The three-foot sample depths may have been too shallow depending upon whether or not the site's surface was capped. 4. The report compares the concentrations of VOC vapors to ESLs. Other than TPHg, we do not use the ESLs from Region 2 since they are in a different climate region and have differing lithology than the Central Valley. We would use CHHSLs for indoor air and a modified V-Leach type model or a gas model that uses Henry's Law to predict groundwater leaching threats from VOC vapors. 5. Using IPA in a steel bowl may not be the best method for determining leaks due to an unknown volatilization rate of the alcohol given the unknown temperature. This means that the IPA gas concentration under the shroud was unknown and therefore ANY IPA detected leak would require a resample. I prefer to use helium as a leak detect compound, so I can gauge the concentration under the shroud with a helium detector and determine how much of a leak there was if helium were to be detected in the sample. If the leak was/is greater than 10%, then a resample would be warranted. However, an IPA sample could have been collected under the shroud for quantitative comparison, but I don't believe it was. 6. Were the vapor samples collected from the former locations of where the dry cleaning equipment was placed?This is typically where the leaks occur and is important when determining potential source areas (if one exists). 7. Just a side note: the text on page 2 of 9 for the preliminary assessment report (third bullet of the groundwater results) showed the wrong units for groundwater samples (84 mg/Kg should have been 84 ug/L). I hope these comments are helpful for you as you move forward with this project. Please keep us informed of these concerns/comments when they are addressed and feel free to call or email me if you have any questions. 1