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lie The llh of the newl installed monitorin wells were surve ed and tied in to the existin wellheads y g y S <br />' monitoring well network, and the depth to groundwater in each well was measured after well <br /> development in order to evaluate groundwater gradients beneath the site A comparison of <br />' groundwater elevation data collected in October 2000 suggests that a slight downward vertical <br /> gradient exists between the shallow aquifer and the 120-foot aquifer Further, an apparent <br />' groundwater depression in the vicinity of well MW4 may be due to the influence of pumping <br /> from the nearby facility well, or may be indicative of downward vertical leakage from the <br />' shallow aquifer through the facility well <br />' Based upon the data collected during this investigation, Ground Zero recommends accelerating <br /> the schedule for installing a new facility well and properly destroying the existing facility well, <br />' which has been documented to be in poor condition Ground Zero also recommends installing <br /> additional shallow groundwater monitoring wells north and northeast of well MW6 to better <br />' define the lateral extent of the dissolved MTBE plume <br /> 2.0 INTRODUCTION <br /> Ground Zero Analysis, Inc (Ground Zero) has prepared this report on behalf of Tuleburg <br /> Warehouse to summarize field methods and results of additional subsurface investigation conducted <br /> at the subject site The investigation was required by San Joaquin County Public Health Services, <br /> Environmental Health Division (PHSIEHD) and consisted of installing five groundwater <br /> monitoring wells, containing liquid and solid waste in suitable containers, developing and sampling <br /> the newly installed wells, disposing of drilling cuttings and fluids, and compiling and evaluating the <br /> data derived from the investigation <br /> 1 <br /> 2.1 Purpose <br />' The purpose of the investigation was to further define the lateral and vertical extent of <br /> groundwater contamination beneath the site from an unauthorized release of petroleum <br />' hydrocarbons from former underground storage tanks (USTs) utilized at the site <br />' 2.2 Resources <br /> Ground Zero geologists Sean Garvey and Justin Power directed drilling and well installation <br /> 2 <br /> data/groundze/tuleburg/reports/mud_has_welireport.doe <br />