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C LEARPATER (1 R O L P [ \ C ErsorrommeVA Sirncs . r� Influent concentrations of TPHg and recovery rates have begun to drop off dramatically through this quarter TPHg influent concentrations have declined from a high of 5,100 mg/m3 in February 1999 to 71 mg/m3 in June 1999 Similarly, average TPHg recovery rates have dropped off from a high of 2 7 lbs/hr in February 1999 to 0 1 lbs/hr in June 1999 (Figure 7) These trends suggest that the remediation system has been successful at removing the majority of gasoline hydrocarbons from the ground If negligible contaminant recovery trends continue throughout the third quarter of 1999 and groundwater contaminant concentrations continue to decline, it is likely that system operation will be terminated at that time Effluent air stream sample results and operational data indicate that the catox unit is operating within compliance of the SJVUAPCD PTO permit#N-386$-1-0 3 2 Operational Data -- Air Sparge System Two air sparge wells (SW-1 and SW-2) are used to inject air into groundwater for the purpose of both volatilizing and enhancing aerobic biodegradation of dissolved-phase hydrocarbons Hydrocarbon vapors removed from the groundwater are recovered and treated by the SVE system For the second quarter, the air sparge system was configured to deliver air to the subsurface via the two sparge wells for 15 m.Lnute intervals every six hours at a pressure of 3 psi lie3 3 System Status -- Soil Vapor Extract=on and Air Sparge System The SVE system is currently configured to extract vapor from wells VW-i through VW-4,MW-1, and RW-I The catox is operated 24-hours per day Beginning in July 1999, the rate of air sparge delivery will be increased to 15 minute intervals every two hour period during daytime hours, in order to achieve maximum recovery of dissolved-phase contaminants at the end of remediation I D-tO7 2Q99 GW&Sys Mon Report 4 July 21 1999