SITE INFORMATION AND CORRESPONDENCE

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26056/26080 Thornton January 1998 Page 2 and Mary Meays of PHS/EHD, it was decided that additional information would be obtained prior to the installation of a permanent monitoring point at depths greater than the 70 feet bgs. The reported grout seal on the Thornton Municipal Supply Well #2 is 70 feet bgs. The additional information will consist of pump test results which have been performed on the Supply Well or that will be performed as part of this investigation. Also, it was decided that additional soil investigation would be required, possibly utilizing cone penetrometer testing, prior to installing the deeper well, so that more accurate lithological information can be obtained. As already indicated, the only information currently available at depths greater than approximately 30 feet bgs was obtained during the 1978 installation of the Supply Well. PHS/EHD requested that ATC collect a grab groundwater sample from the sounding tube using a sanitized disposable bailer. Unfortunately, when this methodology was attempted, it proved unsuccessful because the slant on the sounding tube prevented the entry of the bailer. PHS/EHD requests that an alternate sampling methodology be considered. PHS/EHD also will require that the total depth of the well be measured since it has been indicated that the well was drilled to 420 feet, but only cased to 245 feet. Once the shallow monitoring well, three soil vapor extraction, and the air sparge well is installed and the analytical data obtained from soil sampling, a supplemental work plan will be submitted with describes the remedial action pilot testing. Please proceed with efforts to obtain pre-approval from the State Water Resources Control Board Cleanup Fund for these activities. Also, please submit permit applications for the on site and off site field work along with the $89 fee for each permit. Once the permits have been issued, you may proceed to schedule the approved field activities. Please contact PHS/EHD at least two working days prior to implementing the approved work plan, so that inspections can be scheduled. After the completion of the field activities, PHS/EHD shall be contacted to discuss the samples which will undergo laboratory analysis. If you have any questions or comments or require further information , please do not hesitate to contact me at (209) 468-0337. Donna Heran, REHS, Director Environmental Health Division Mary Meays, Senior REHS Site Mitigation Unit cc: Pat Anderson, CVRWQCB cc: Teresa Trinh, SWRCB cc: Ron Rail, SJC Utilities Maintenance District cc: Dean Gilman, SJC Public Work Department cc: Tom Lutterman, Smith-ATC Environmental cc: Al Hoslett, Esq. Margaret Lagorio, REHS Supervisor