ARCHIVED REPORTS XR0006515 - Laserfiche WebLink

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It is felt through vapor extraction and limited over-excavation of the UST area that the source (soil contamination) at this site has been removed and the soils portion of the remedial action efforts has been accomplished and that no further actions are necessary GROUNDWATER Grab water samples obtained on June 4 and 5, 1997 from soil borings SBS, S136 and S137 were compared to the historic water samples obtained on December 7, 1988 from SB2 and S133, see Table and Charts in CONFIRMATION OF THE EFFECTS OF THE VAPOR EXTRACTION SYSTEM, dated July 31, 1997 Comparing S133 to SB6 a 93% reduction in the amount of TPHg has been accomplished Benzene, Toluene and Ethylbenzene have been reduced to below laboratory lower detection limits and Xylenes have been reduced by 99% Similar reductions can be seen when comparing SB2 with SB5 and SB7, or 92% and 85% for TPHg respectively While Benzene, Toluene and Ethylbenzene have been reduced to trace amounts Xylenes have been reduced to 54% and 13% of their original values respectively Confirmation soil boring S137 was converted into a two inch PVC well MW13 This well and MW1, MW2, MW3 and MW 10 are currently being used for vapor extraction MW2 and MW13 are also used for air sparging (commencing on October 9, 1997) It is anticipated that sparging of these wells will introduce and make oxygen available for biodegradation of the down gradient wells MW8 and MW12 Prior to shutting off the air sparging vapor extraction system on December 8, 1997, MW2, MW8, MW9 MW12 and MW13 were tested for the amount of DO in the groundwater Sparging had saturated MW2 and MW13 with oxygen, they registered 9 1 and 7 6 mg/L respectively Upgradient well MW9 contained 4 1 mg/L while downgradient wells MW8 and MW12 contained 1 3 and 1 8 mg/L Once the sparging and vapor extraction is turned off, the DO in the groundwater is used up almost immediately, see Figures 9 and 10 It is unclear at this time if the DO found in wells MW8, MW9 and MW12 is a result of vapor extraction, sparging or the combination of both The gasoline range hydrocarbon plume associated with this site is declining in concentration and should continue to do so. since the removal of the source in the soils beneath this site, see Figures 5. 6, 7 and 8 With continued vapor recovery, the bio venting of MW8 and MW12 and the commencement of sparging at MW2 and MW13, the reductions in groundwater concentrations should continue to decline at MW8 Similar effects should be seen at MW12 during the May, 1998 Quarterly sampling 6 R603 Update#515/98