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Andrew Keller - 2 - 1 June 2007 research and information to show that the landfill contains "stranded water" and not groundwater. 5. Comment: In WDRs Finding No. 20 and 21 and in Sections D.1.a-b, the Discharger requested a new interpretation of the 50 -foot saturated zone and requested that the zone be referred to as the "Regional Aquifer". Response: The Discharger's updated information on the zones of saturation was included in WDRs Finding No. 19, 20, and 21. However, renaming of the 50 -foot saturated zone as the "Regional Aquifer" was not included in the WDRs nor in the MRP. Based on data provided, it is unclear what the interaction between the different saturated zones are and whether the 50 -foot saturated zone is truly the top of the "Regional Aquifer". 6. Comment: In WDRs Finding No. 25 and 26, the Discharger requested that lower concentrations of waste constituent (obtained recently from the 50 -foot saturated zone) be included in the findings. Response: The Discharger's lower concentrations were not included in the findings. The presented concentrations demonstrate potential impacts, and that concentrations could be as much as, or more than, those stated in the findings. 7. Comment: In WDRs Finding No. 28 and Section D1.a, the Discharger requested that existing soil -gas probes be removed from the WDRS and be replaced with perimeter methane monitoring probes that have not been installed. Response: The movement of landfill gas containing VOCs is a mechanism for the transport of VOCs to groundwater. Therefore, in order to evaluate the potential transport of containments by soil gas, the soil -gas monitoring probes need to be retained as stated in the WDRs and sampled, as required in the MRP. However, the Discharger may install the new methane probes. Staff will review the Well Installation Workplan and provide comments or concurrence on soil gas sampling locations. Once the perimeter methane probes have been installed, the Regional Water Board staff may revise the MRP to include sampling of these monitoring points. If you have questions, please contact me via email (mboyd(cD_waterboards.ca.gov) or telephone at (916) 464-4676. Mary L. Boyd Water Resources Control Engineer San Joaquin River Waste Discharge to Land Unit cc: Robert McClellan, San Joaquin County Environmental Health Division, Stockton Jeffrey D. Bennett, Miller Brooks, Huntington Beach Dave Otsubo, CIWMB, Sacramento MLBAMCovelcclf-response-2-comments.doc