ARCHIVED REPORTS XR0006468 - Laserfiche WebLink

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REG 603 UPDATE-9 9/14/92 4 .0 DISCUSSION AND CONCLUSIONS As stated in earlier reports , the soil is contaminated with gasoline range hydrocarbons beneath the tank field (MW10 ) and along the capillary fringe of the ground water , (MW1 , MW2 , MW3 and ! � ]I MW10 ) . Ground water beneath the site contains the dissolved constituents of gasoline range hydrocarbons and has spread out from beneath the site to the north (MW-6 ) , to the south (MW-7 ) to i the west (MW-9 ) and to the east (MW-8 ) . The latest ground water samplings , March 10 and June 18 , 1992, have shown a decline in the lateral extent of the plume, see Figure 5 (6-18-92 ) . vapor extraction commenced on October 17, 1991 and up until September 3, 1992 has operated for 4201 .5 hours out of a possible 7024 for a 60% run time, destroying 27, 554 pounds of gasoline range hydrocarbons . Since the last status report, June 22, 1992, a total of 3114 pounds of gasoline range hydrocarbons have been removed/destroyed. DCE, TCE and PCE screening indicates that i these compounds are not present in the vapor stream at this site. Ground water elevation measurements show that the ground water is being mounded at the lower K value wells MW3 and MW10 , while the � II overall flow direction is to the northeast and southeast. Ground water sample results obtained on December 17 , 1991 , approximately 1473 hours after commencement of vapor extraction, compared to the ground water sample results obtained on June 18 , 1992 , 5885 hours after commencement of vapor extraction, show a t ; decline in the extent of the dissolved constituents In all of the monitoring wells except MW1 , MW3 and MW10 which have floating product, see Table 1 and Figure 5 . It is felt that once the air dilute has been completely closed and all vacuum recovery can be directed to MW1 , MW2 , MW3 , MW10 and EX- 41" , an increase in the vacuum influence will be obtained and a more substantial reduction in the contaminants , found in the other wells , will be noted. The permit to dump treated ground water to the sewer has been recieved and once completion of the ground water recovery - treatment system has been completed, pumping will occur from monitor wells MWI and MW3 . Treatment will be tank stripping, utlllzing the "Convault" as a i nnn rra i 1 nn +anlr str 1pper +n '-...-� w J✓M 4+11 treat approximately 300 gallons every 5 hours . All vapors driven off of by the air stripping from the tank will be processed into the thermal oxidizing unit for destruction, see Appendix D -- Water Discharge Permit . . As directed by San Joaquin County Health a workplan has been II PAGE 9