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Former Beacon Station 494 Stockton,California July 19, 1995 Quarterly Remediation Status Report shut down on June 12 The VES will remain shut down pending an evaluation of the need to contmue vapor extraction During each routine visit, the differential pressure, vacuum, and influent and effluent hydrocarbon reading and temperatures were recorded to evaluate and calculate flow and hydrocarbon emission rates The influent and effluent hydrocarbon reading were measured in the field during each site visit with an infra-red Honba Hydrocarbon Analyzer These reading were measured before the vapor stream entered the blower and again after as it exited the final carbon vessel Influent and eluent vapor stream samples were collected with a sampling pump into Tedlar bags and transported under chain of custody to Western Environmental Science and Technology Laboratory in Davis, California Samples were analyzed for total petroleum hydrocarbons as gasoline(TPHg)by Environmental Protection Agency (EPA) method 8015 and benzene, toluene, ethylbenzene, and xylenes (BTEX) by EPA method 8020 The laboratory results for TPHg and benzene concentrations are summarized on Table 1 included with this report Copies of this periods laboratory reports and chain of custodies are mcluded in Attachment A During this reporting period TPHg destruction efficiencies ranged from 15% to 98% Benzene destruction efficiencies ranged from 95% to 100% Influent concentrations of benzene were generally at or below laboratory detection limits Since the system started approximately 13,401 lbs of TPHg and 212 lbs of benzene have been removed from the subsurface VES extraction and emission data are summarized in Table I GWTS During this reporting period the GWTS operated two of the three months The system was not operating in April The GWTS discharged approximately 66,376 gallons of groundwater Influent and effluent groundwater samples were collected twice per month and analyzed for TPHg and BTEX Average flow rates ranged form 0 95 gallons per minute (gpm)to 1 93 gpm Laboratory results indicated that discharged groundwater during this period had concentrations of TPHg ranging from 490 parts per billion (ppb) to below the laboratory detection Limit and benzene ranging in concentrations from 26 ppb to below the laboratory detection smut A summary of the GWTS data is shown on Table 2 with this report A copy of the GWTS laboratory reports and chain of custodies are included in Attachment A Report No 494rsrpt95 q2 Job No 1494 31 2 HORIZON ENVIRONMENTAL INC