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+q Extended Investigation of Groundwater Quality - 152 East 11th Street, Tracy Page 6 II WELL HEAD SURVEY On July 8th, 1993, the locations, top-of-casing elevations and the ground levels at the well heads of all wells installed at the 152 and 153 East 11th Street sites were surveyed relative to the top of the casing of well ULT 7 A local datum of 50 00 ft was previously established, by others, on the top of the ULT 7 casing to provide a reference for measurement of groundwater table elevations The July 8th survey was conducted to tie the locations and well head elevations of the newly installed wells to this datum and to ensure that the positions and well-head elevations of all wells m the combined array that have been constructed at vanous tunes for the Navarra and Ultramar properties can be related to this common reference The locations of all wells are shown on Figure 2 and the well-head elevations are recorded in Table 2 GROUNDWATER SAMPLING AND ANALYSIS On May 13th 1993, on behalf of the Navarras, The San Joaquin Company submitted a . Groundwatcr Sampir�r g Plan - Property at 152 EMt 11th Street Tracy. California to the SJCPHS The plan provides for an integrated sampling program for the complete array of wells that have been installed at the Navarra property at 152 East 11th Street and at Ultramar's Beacon station at 153 East 11th Street The first phase of the plan is a comprehensive round of sampling of all wells in the combined array This is to be followed by periodic rounds of sampling from selected wells to monitor arty seasonal variations in the plume of groundwater that is affected by hydrocarbons The sampling plan has been approved by the SJCPHS The Navarras and Ultramar Inc have entered into a non- binding agreement for technical cooperation to implement the plan and share the costs i In compliance with the approved sampling plan, on July 8th 1993 the depth to groundwater in each of the monitoring wells was measured using a conductivity probe These depth are recorded in Table 3 which also gives the water table elevations computed relative to the local datum on the top of the casing of Well ULT 7 After the depth to groundwater had been measured, each well was purged by pumping a minimum of five well volumes of water from them The purge water has been stored in a closed 1100 gallon PVC tank on the 152 East Street property where it will be stored until sufficient for volume has been accumulated for its economical disposal at a permitted facility When Well ULT 8 was opened for purging it was found that it only a few inches of water were apparently present in it above an accumulation of sort at a depth of approximately 8 3 10 ft This is consistent with reports from previous attempts to sample this well that has been reported by others to have been dry from July 1991 to March 1993 However, the well log for this well mdreates that is 25 ft deep (Refer to Appendix A) This is much greater than the depth to the water table in the area, which is typically found between 7 and 9 ft