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3.0 VAPOR EXTRACTION SYSTEM OPERATION AND MONITORING 3.1 System Operation, During the quarter, the system operated for a total of 1738 hours (Appendix A) It operated for 26 days in January, 29 days in February, and 26 days in March During that period, 4,608,404 cubic feet of vapor were extracted This brings the total to over 48,000,000 cubic feet since July 1994 3.2 Monitoring Summary The extraction unit's on-board computer monitors several important parameters of engine performance, t 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 concentrations in the vapor stream (influent soil gas) and effluent (combustion products) were manually monitored on a weekly basis with a Microtip HL2000 photo-ionization detector In addition, vapor samples were collected from the effluent line and combined influent line on January 2 for comparison to the PID readings on that date 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 0 and 36 ppm during the quarter, and tended to follow upward or downward trends in inlet concentrations PID readings in the inlet stream ranged from a high of 2,370 ppm in the deep well in mid-February to a low of 27 ppm in the deep well in early January 1 ' 4 0 DATA ANALYSIS 4.1 Graphical Summary ' Monthly summaries of daily air flow rates and other parameters for the first quarter are included in Appendix A In order to graphically illustrate the operation of the system, data for air flow rate and total cubic feet of extracted vapor since January 1995 are plotted in Figures 3 and 4 PID readings and laboratory results of vapor samples are graphed in Figure 5 to illustrate the effect of the system on soil vapor concentrations ' Flow rates for the quarter ranged from a low of 11 cfm to a ]nigh of 49 cfn For most of the quarter, the unit operated efficiently at rates above 40 c1m Early in the quarter the unit operated poorly, but operation improved after a timing belt was replaced in late January ' During the fourth quarter of 1995 vapor concentrations s showed a general decrease This trend reversed during the first quartet:of 1996, as concentrations climbed from below 500 ppm to 1500 ppm in late March This trend appears to indicate that air sparging in the deep extraction well, which began ' 3