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25 March 1991
<br /> page 2
<br /> C Rogers
<br /> Chevron U.S.A. Inc.
<br /> operation of the treatment equipment,effluent samples from both the thermal and
<br /> per pmen PCD permit requirements, initial vapor
<br /> personnel on the ape operating parameters were
<br /> catalytic oxidizers were analyzed as p
<br /> concentrations fromeach well of balancing flow thrre ough the aextraction wells and treatment system
<br /> recorded,and the
<br /> was established•
<br /> Ex n m r i n n Effi ien
<br /> wells V3,
<br /> erated
<br /> Since the beginning of operation, the extraction system has for a total sy e n extraction razz of
<br /> MW4. Each well is operated at 33 cubic feet per minute(efmfor
<br /> 100 cfm. Figures 1-5 show estimated hV�po�bon contentation contours
<br /> the soils,i t was determined that
<br /> closest to the source of the petroleum hydrocarbon release,would be used
<br /> depths. From this estimate of petro Y
<br /> these three wells,being drocaibon dispersion and shrink the plume back to its origin.
<br /> initially to reverse the direction of by
<br /> fume of sail to remediate and a longer cleanup time.
<br /> Six wells
<br /> This was done to avoid the possibility of moving the major bulk of the hydrocarbons into less
<br /> impacted soils,thus creating a large
<br /> the major mass for the ydrot oern willhbe used to extraeen ct vapors these three ells,
<br /> connected to the extra Y
<br /> my OfPetroleum,hydrocarbon constit ontsVH)from
<br /> Table i summarizes the concentratiwCIAS
<br /> ons(pp p g�500,and 14,000
<br /> Used for vapor extraction at the sit e. Concentrations
<br /> iianit al concentrations of 5,1100 bonavera a vapor
<br /> us and MW4 have declined f Phis represents an g
<br /> wells V3,VS, 200, and 1,600 ppm. respectively (Figure 6).
<br /> ppm to 590, 1, ercent. This vapor phase concentration reductionis,
<br /> libratien of
<br /> concentration reduction of 87 pthe extraction This
<br /> temp y• and va or phases takes place.
<br /> re-
<br /> temporary. As Figure
<br /> f=ee,dissolved, adsorbed, and rspshut off; a re-eq
<br /> hydrocarbons betweenreplenishes the concentration of hydrocarbons in the vapor phase at
<br /> redistribution of hydrocarbons rep period have been implemented to
<br /> period from 28 December 1990 throng 99$. During
<br /> January
<br /> the expense of the other three phases. Two re-equilibration p h 19 February .
<br /> date. The first took place over the -day
<br /> dfrom 28 January
<br /> 1991 and the second over the 22-da., P
<br /> e first re-eq and 3,800 ppm, respectively. The conce o
<br /> uilibration period the concentrations in wells V3,V5;acid MW4 increased from 44 ,
<br /> the 400 ppm to 1,400, 3,.00,
<br /> 1,000, and 1, eriod. During the sewn re-equilibrationd
<br /> in�rcased by an average factor el three over the 21-day p only an average
<br /> period the concentrations in wells Vect vel . The concentrations from
<br /> by o and
<br /> i ave,400 rage
<br /> to 860, 1,800,and 2,500 ppm,resp period-factor of two over the second 22-day p
<br /> -i concentrations over the 61 days of os benzene. The conCratl centrat on been associated with
<br /> The decrease in
<br /> TVI
<br /> -I
<br /> in the concentrations of other constituents initial
<br /> a m able 1). This
<br /> benzene s in Wells V3,V5,and MW4 have decline
<br /> tlianothe detection Iim concentrations
<br /> 1 ppm
<br /> (Table
<br /> and h
<br /> Ppm,respectively,to no concentrations gr
<br /> the
<br /> decrease in benzene concentrations reduces he;lth risks.
<br /> The vapor eoncentratio
<br /> ns of the other six extraction wells havealsoibeen
<br /> e wells has been during en
<br />_..-
<br /> _....._ _.. _._. . __._. _. operation of the VETS..As Table 1 shows,the concentration a and 6;2001:pmv to 1, .._._... _...._._ _..._._ _.._. __._....
<br /> V5 aril MW4: The concentrations in wells V 1,V2,V4,M ,
<br /> more dramatic than for wells V3,V5,
<br /> and
<br /> and MW6 have declined from 4,700, 6,700,9,300, 16,000, 13,000,
<br /> i
<br />
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