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Unocal Service Station #6981 April 25, 1995 iThe TPHg concentration in influent vapor stream sample was 6,100 milligrams per cubic meter (mg/m'), and the benzene concentration in this sample was 99 mg/m3 The TPHg concentration in the effluent vapor stream sample was 160 mg/m3 TPHg destruction efficiency 97 38%, and the TPHg emission rate was 3 46 pounds per day (lb/day) The effluent benzene concentration was 0 83 mg/m3, with a destruction efficiency of 99.16%. The benzene emission rate was 0 018 Ib/day Disposal of Water Water removed from the influent vapor stream by the moisture separator is stored in steel drums which are locked inside the VES compound On March 3, 1995, Armour Petroleum removed approximately 103 gallons of accumulated water from two drums Copies of the Armour Petroleum field data sheets are presented in Appendix E DISCUSSION The VES was brought online September 22, 1994 As of January 23, 1995, when the VES was shut down, the VES had operated approximately 116 days, or 94% of the time. All of the vapor extraction wells were open and used for extraction until January 23, 1995 The VES was in compliance with all SJVUAPCD permit requirements regarding TPHg emission rates and destruction efficiencies Through January 9, 1995, approximately 4,413 . pounds of hydrocarbons (TPHg) have been extracted from beneath the site The shallow groundwater table beneath the site rose approximately 2 75 feet in the first quarter 1995 as compared to the fourth quarter 1994 Analytical results from groundwater samples indicate the concentrations of TPHg and BTEX decreased from the fourth quarter 1994 to the first quarter 1995 sampling event Wells with the highest concentrations of dissolved gasoline are located in the vicinity of the eastern most dispenser island The analytical data from the surrounding wells continues to indicate that the dissolved hydrocarbon plume beneath the site is delineated with regard to dissolved benzene As requested by the SJVUAPCD, GSI submitted a application for modification of the emission unit from thermal to catalytic mode We anticipate approval from SJVUAPCD by March 1995 Upon receipt of the modified permit the emission unit will be modified and restarted During the next quarter (second quarter 1995), the groundwater monitoring wells will continue to be monitored and sampled Upon approval of the SJVUAPCD, the VES will be switched to catalytic operation anode and restarted The Second Quarter 1995 Status Report will be submitted to the appropriate regulatory agencies by July 31, 1995 4855 02-3 3