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r� <br /> The major change in TPHg for monitoring well MW-8S is a mystery.A drop from TPHg= 14,000 ppb <br /> to TPHg=ND in six months is very unusual. 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. IfMW-8S was on the very southeast edge of the plume,this <br /> change in gradient direction may move the plume outside of the monitoring area of the well. <br /> Recommendations <br /> The author recommends that monitoring well sampling continue on a quarterly basics. It is also <br /> recommended that a 15"diameter pump test well be installed to determine the permeability of the 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 of this office at(209)368-9381 ifyou have any questions on this report. <br /> Respectfully submitted, <br /> Foothsl En eeri <br /> Q � Es&a,� <br /> rvin Ri bur , P No. 187 . <br /> 1FOF <br /> cc: Michael D. & Sharon Ol var z, 436 W. Scotts Av. Stockton, Ca. <br /> f. <br /> 3 <br />