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Ms. Laurie Cotulla October 4, 1991 <br /> Tri Valley Growers, Thornton, CA Page 2 <br /> Response: The laboratory results for TPHG for MW-1 ir. table 3 were incorrect. <br /> The correct TPHG concentration is 360 pp'o. A corrected tab.'e 3 is <br /> enclosed fory our records. <br /> 4. Question: The report stated that dedicated pneumatic pumps were used to sample <br /> each well. It is the understanding of PHS/EHD that only MW- <br /> 4/extraction well (IAW4/EW)contains a dedicated pneumatic pump. <br /> Please clarify the use of dedicated pneumatic pumps. <br /> Response: W1 are using dedicated submersible pumps to purge and sample the <br /> iitoring 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 ftlter#2. At a much reduced flow rate, <br /> MW4/EW was pumped dry several times in the presence of PHS/EI1D <br /> representative. <br /> MW4/EW has a two inch diameter and thin is not designed for <br /> extraction purposes as was indicated by the August 1, 1990, <br /> CVRWQC$ letter and by the October 15, 1990, PHS/!FM Ietter. 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 to <br /> warrant-.a.new....welI..... I am..enclosing...some information.from David -- -------------------.--.- <br /> TQRIM2.WP <br />