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Nis.. Laurie°Cotulla October 4, 1.991 <br /> Tri,'Valley Growers, Thornfon; 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 ?HS/EH D that.only MW- <br /> _ _ -4/extraction well (MW4/EW)contains_ a dedicated pneumatic pump. <br /> Please clarify the use of:dedicated'pneumatic pumps. <br /> t -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 />'f shed:- Enclosed is a flyer on the pumps. <br /> 5_. <br /> 'Question: During the-August 16, 1991 site inspection, PHS/EHD observed the <br /> effects of:pumping of MW4/EW7at: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 /> I` <br /> carbon-filter#1 and. carbon_filter.#2. . At a much.reduced flow rate, <br /> MW4/EW was pumped dry-several times in the presence of PHSIEHD <br /> representative. <br /> MW4/EW has a two inch diameter and thus is not designed for <br /> - extraction purposes... as was indicated .by the_:-August 1,. . 1990, <br /> CVRWQCB letter and by the October 15, 1`990;-PHS/EHD letter: It <br /> may: be-necessary.-m° the future m-install a izi6r6=effective extraction <br /> well: -. <br /> Monthly status reports are requested;.initiallyfor one quarter, to-review. <br /> the .adequacy of the :groundwater remediation system in .operation.. <br /> Submit.:the first monthly status reportwithin 30 days of the date.of this <br /> -letter. <br /> - Response: On:August-16, 1991,.a WaterWoik-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 l5kk <br /> operational: In-low:flow regimes, like_the. Thornton area, the'use of <br /> - four inch-40ls will :not increase-:.the-°vells.effectiveness enough..'to <br /> warrant_a_ new' well: I= am enclosing some information -from David <br /> I` TQR1002.WP <br />