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Canepa s Car Wash 6230 Pacific Avenue,Stockton CA Second Quarter Groundwater Monitoring Report,May 2006 Page 5 of 8 • TREATMENT SYSTEM STATUS UPDATE Installation of the pump and treat system and upgraded SVE system was completed in September 2004 The City of Stockton Municipal Utilities District (MUD) authorized the initiation of discharge of treated groundwater on October 28, 2004 Groundwater extraction and treatment, with subsequent discharge to the sanitary sewer,began November 1, 2004 The system remained in normal operation during February 2006 However, during March and April 2006, several unscheduled, automatic shutdowns by the system's built-in safety features also occurred, generally related to blown fuses and a malfunctioning flow meter In addition, the carbon unit was changed out twice during April and May 2006 MASS REMOVAL AND DESTRUCTION CALCULATIONS The system was operating for approximately 1,427 hours between January 31, 2006, and May 18, 2006, or approximately 56% of the time The effects of the system auto-shutdowns and system maintenance shutdowns referred to in the previous section are reflected in the mass removal and destruction calculations Operational and efficiency data are included in Attachment D Aqueous Phase Mass Removal The groundwater treatment system has removed petroleum hydrocarbons from 376,792 gallons of groundwater during the second quarter of 2006 Groundwater treatment system samples and associated data were collected to comply with the Self-Monitoring Sample Program of the MUD Groundwater Discharge Permit, as well as to monitor the operational efficiency of the system and the consumption of carbon (Attachment D) Groundwater is pumped from the subsurface via extraction wells MW-1 and MW-11 MW-1 has contributed approximately 95% of the total groundwater influent into the treatment system The concentrations of BTEX, TPH-G, and MTBE detected in samples collected from MW-1 have been increasing as anticipated and discussed above A total of 1,912,290 gallons have been treated by the system as of May 18, 2006 Calculations indicate that approximately 65 41 pounds of gasoline were removed from the groundwater at the Site during the second quarter of 2006 Furthermore, an approximate total of 372 5 pounds of gasoline have been removed since the system was made operational A calculation worksheet is included in Attachment D Vapor Phase Quantification Methodology Soil vapor mass removal and destructive efficiency calculations are made using the following methodology - Field photo-ionization detectors (PID) measurements are collected weekly and laboratory samples are typically collected and analyzed monthly The data is compiled and a correction factor is calculated between corresponding PID measurements and laboratory analytical results _ The correction factor ,s then applied to the PID mPasivements So they more accurately represent projected laboratory results on a weekly basis The corrected values are averaged, then the units of measurement are converted from parts per million of volume (ppmv)to milligrams per cubic meter(mg/m) The average contaminant concentration for the period is then multiplied by the total volume processed through the treatment system to yield total mass CONDOR