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• ? 4; <br /> hydraulic gradient direction of northeast from the southeast direction of last quarter.The slope of the <br /> hydraulic gradient has increased to S=.003 for this event, from 5=.0026 of the last event. <br /> The major change in TPHg for monitoring well MW-9 to non-detect may mean that the monitoring well <br /> water was contaminated during construction. In three quarters the TPHg has changed from a high of <br /> 2880 ppb. to non-detect. The drop from TPHg = 14,000 ppb in the first quarter to TPHg = ND in <br /> monitoring well MW-8S continues this quarter. This monitoring well is positioned to monitor a very <br /> permeable aquifer at sixty feet of depth. The only physical change during this event is the slope and <br /> direction of the surface hydraulic gradient. <br /> Recommendations <br /> The author recommends that monitoring well sampling continue on a quarterly basics. It is also <br /> recommended that a 15"diameterpump test well be installed to determine the permeability ofthe sand <br /> aquifer that lies between 50'and 65'feet of depth.The permeability ofthis aquifer is required to design <br /> a suitable and effective groundwater pump and treat system. <br /> Please contact Ervin Rifenburg ofthis office at(209)368-9381 ifyou have any questions on this report. <br /> Respectfully submitted, <br /> Foot ine RpVEs � <br /> Ervin Rifen urg, Exp. <br /> QFC <br /> cc: Michael D. & Sharon Olivarez, 436 W. Scotts Av. Stockton, Ca. <br /> • <br /> 3 <br />