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CLEARWATER <br /> h R 0 U P I \ L <br /> En=rro ante rrt a! Sept r, <br /> Influent TPHg concentrations this quarter remain near the method detection limit following a rapid drop-off during the <br /> second quarter 1999 TPHg influent concentrations have declined from a high of 5,100 mg/m3 in February 1999 to <br /> between 22 and 28 mg/m3 for the period from July trough September 1999 Similarly, average TPHg recovery rates <br /> have dropped off from a high of 2 7 lbs/hr in February 1999 to 0 02 lbs/hr in September 1999 (Figure 7) These trends <br /> suggest that the remediation system has been successful at removing the majority of gasoline hydrocarbons from the <br /> ground,and the effective limit of the system has reached a plateau <br /> Effluent air stream sample results and operational data indicate that the catox unit is operating within compliance of the <br /> SJVUAPCD PTO permit#N-3868-1-0 <br /> 3 2 Operational Data -- Air Sparge System <br /> Two air sparge wells (SW-1 and SW-2) are used to inject air into groundwa€er for the purpose of both ,olatilizing and <br /> enhancing aerobic biodegradation of dissolved-phase hydrocarbons Hydrocarbon vapors removed from the groundwater <br /> are recovered and treated by the SVE system For the second quarter, the air sparge system was configured to deliver air <br /> to the subsurface via the two sparge wells for 15 minute intervals every six hours at a pressure of 3 psi <br /> 3 3 System Status -- Soil Vapor Extraction and Air Sparge System <br /> SVE/AS system operational data indicate that the recovery of hydrocarbons from the subsurface has become negligible <br /> with the use of the existing remediation unit Since October 1998, approximately 7,377 lbs of gasoline hydrocarbons <br /> have been received form the subsurface Operational data over the last several months indicates that the system, as <br /> configured,has achieved a plateau in contaminant recovery Inn light of this information, Clearwater and SJCPHS/EHD <br /> discussed shut-down of the existing Selleco ECAT 250 treatment equipment at the end of September 1999 The <br /> SJCPHS/EHD concurred with this recommendation in correspondence dated September 20, 1999 <br /> • <br /> D-107 3Q99 GW&Sys Mon Report 4 September 29, 1999 <br />