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' (�ealo tcal Technics Inc <br /> � Page 2 <br /> Groundwater Monitoring Report <br /> Project No 723 2 <br /> November 13,2003 <br /> GTI recommends that interim remediation be considered before this plume migrates any <br /> further and the cost for cleanup continues to increase We submitted our September 8, 2003 <br /> ' "Feasibility Study Work Plan - Dual Phase Soil Vapor and Groundwater Extraction Pilot <br /> Test" to evaluate a remedial alteinative that could be economically used on this site We <br /> have not yet received a response from the San Joaquin County PHS/EHD <br /> 1.0 GROUNDWATER MONITORING <br /> 1.1 H dro eolo of Site <br /> Y g gJ' <br /> A site-specific groundwater gradient and bearing were calculated from computer-generated <br /> contours The groundwater was flowing N60°E at a gradient of 0 0058 ft/ft The average <br /> elevation of groundwater at the site was 26 63 feet below mean sea level This represents a <br /> decrease of 3 82 feet since the June 2003 monitoring event <br /> ' Figure 2 is a groundwater gradient map for the September 12, 2003, event Figure 3, <br /> Groundwater Gradient Rose Diagram, includes historical groundwater directions and <br /> gradients <br /> Table 1 in Appendix A contains the groundwater elevations and gradients for the site <br /> ' Vertical Groundwater Gradients <br /> Under vertical groundwater flow conditions, the water level in a monitoring well is a <br /> function of the length of the well screen and its depth or vertical position in the aquifer As <br /> with horizontal flow conditions, the diameter of the well or piezometer is immaterial A <br /> vertical gradient was calculated for well pair MW-3/MW-201 These wells are located <br /> approximately 5 feet apart <br /> The following procedure is used to calculate vertical groundwater gradient <br /> ' • Determine vertical distance between the two measuring devices by the distance from the <br /> mid-point between the top and bottom seal of the deep well (MW-201) and the mid- <br /> point between the groundwater elevation and the bottom seal in the shallow well (MW- <br /> 3) <br /> • Measure the head in both wells used in the calculations <br /> • If the lateral distance between the well pair is greater than a few feet, then calculations <br />' must be made to correct the down-gradient piezometric head to account for the sloping <br /> water table between the wells The calculation considers the slope of the water table and <br />' the distance in a down-gradient direction between the two wells used in the calculations <br />