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2.4 Recent Investigation During the fourth quarter of 1996, Emcon of Sacramento drilled two new soil borings to gather data ' for preparation of a Risk-based Corrective Action Plan One boring is located near MW-5, and one is located approximately 15 feet east of VE-1 This boring was completed as a vapor extraction well and has replaced VE-I "deep" The new,well is screened from 35 to 55 feet and is referred to in this ' report as VE-2 ' 3.0 VAPOR EXTRACTION SYSTEM OPERATION AND MONITORING ' 3.1 System Operation During the quarter, the system operated for a total of 585 hours (Appendix A) It operated for part ' or all of 9 days in January, 10 days in February, and 17 days in March During that period, 1,175,720 cubic feet of vapor were extracted This brings the total to approximately 62,000,000 cubic feet since July 1994 The Air Quality Managment Distract operating permit expired in ' January, and the unit was therefore shut down on January 10, 1997 The Permit to Operate was extended and the unit was restarted on February 6, but combustion could not be maintained and for the next 9 days the unit operatbd for only a few hours Apache maintainence personnel located a ' malfunction in late February and repaired the unit in early March Since the;middle of March, it has performed normally 3.2 Monitoring Summary The extraction unit's on-board computer monitors several important parameters of engine ' performance, including air flow rates, well vacuum, and volume of extracted vapor These data are recorded hourly and averaged over the 24-hour day The daily averages are shown in Appendix A ' Hydrocarbon concentra#ions in the vapor stream (influent soil gas) and effluent (combustion products) were manually monitored 4 times during the quarter with a Microtip 2020 photo- ionization detector In addition,vapor samples were collected from the VE-1 "shallow" influent line and four the VE-2 influent line on March 26 The samples were collected in tedlar bags and delivered to Sequoia Analytical for analysis of TPH-g and BTEX concentrations The results, ' reported in milligrams per cubic meter, are shown in Appendix B PID readings at the exhaust port ranged between 5 and 12 ppm during the quarter Effluent readings ' did not follow upward or downward trends in inlet concentrations PID readings from VE-2 ranged between 1,000 and 2,000 ppm, and readings from VE-1 "shallow"ranged from 700 to 1200 ppm i 3 1 , 1