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• i <br /> _ y <br /> r <br /> Ml . Lau.= Cotalia October 4, 1991 <br /> Tri Valley Growers, Thornton, CA Page 2 <br /> Response: The laboratory results for TPHG for MW-1 in table 3 were incorrect. <br /> The correct TPHG concentration is 360 ppb. A corrected table 3 is <br /> enclosed for your records. <br /> 4 Question: The report stated that dedicated pneumatic pumps were used to sample <br /> each well. It is the understanding of PHSIEHD that only MW- <br /> 4/extraction well (MW4/EW)contains a dedicated pneumatic purnp. <br /> Please clarify the use of dedicated pneumatic pumps. <br /> Response: We are using dedicated submersible pumps to purge and sample the <br /> monitoring wells. The pumps are stored on site inside the treatment <br /> shed. Enclosed is a flyer on the pumps. <br /> 5. Question: During the August 16, 1991 site inspection, PHS/EHD observed the <br /> effects of pumping of MW4/EW at a rate of 1.8 liter per minute. The <br /> pump had been pumping a portion of air prior to the arrival of <br /> WaterWork representative as evidenced by the low water volumes of <br /> carbon filter#1 and carbon filter#2. At a much reduced flow rate, <br /> MW41EW was pumped dry several times in the presence of PHSIEHD <br /> representative. <br /> MW4/EW has a two inch diameter and thus is riot designed for <br /> extraction purposes as was indicated by the August 1, 1990, <br /> CVRWQCB letter and by the October 15, 1990, PHSIEHD letter. It <br /> may be necessary in the future to install a more effective extraction <br /> well. <br /> Monthly status reports are requested, initially for one quarter,to review <br /> the adequacy of the groundwater remediation system in operation. <br /> Submit the first monthly status report within 30 days of the date of this <br /> letter. <br /> Response: On August 16, 1991, a WaterWork Field Technician found a defective <br /> pressure switch which resulted in a higher pumping rate that evacuated <br /> the well. The pressure switch has been replaced and the system is back <br /> operational. In low flow regimes, like the Thornton area, the use of <br /> four inch_ wells-will not increase the wells effectiveness-enough-io _ - _. _. _.......... <br /> warrant a new well. I am enclosing some information from David <br /> TQR10M.wP <br /> t, <br /> ,i <br />