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' Report-Pilot Remedial Svstem Test Page 24 Former Manna Pro Site ' Project No 2011 July 31, 2000 r Prior to commencement of air sparging but after the vapor extraction system had been activated, PID measurements of the extracted vapor from VEW-1 yielded readings which ranged between 52 and 33 ppm (from 05122100) During the operation of the air sparging system (from 05130100-06101100), the OVM readings from VEW-1 displayed a generally increasing trend from 52 to 109 ppm on 05130 to 109 to 120 ppm on 05131 and 147 to 290 ppm on 06/01 It is interesting to note that the project high OVM readings were noted upon restart of the VES system after 05130, after the sparge system had run overnight As shown in Summary Table 6, during the period that air was injected into the sparge ' well (ASW-1) there was a marked increase in dissolved oxygen content in groundwater samples from wells 013-2 and 013-3 OB-1 displayed a slight increase in dissolved oxygen while samples from OB-4, OB-5, and MW-6 remained generally unchanged The well nearest the sparge point, OB-3 showed the greatest increased in dissolved oxygen content The increase in dissolved oxygen in the wells 013-1, OB-2, and OB-3 was obtained by subtracting the background, or original oxygen content, measured prior to air ' sparge system start up, from the maximum level It was assumed that the increase in oxygen was due entirely to the effect of sparging The increase in oxygen concentration . was plotted against the respective distance each well from the sparge point The data points were plotted on a log-normal scatter chart chart (Figure 9) A linear regression, best fit curve was calculated in the Excel software and the radius of influence from sparging was taken as the intersect of the trend line with the 0 point of the oxygen increase Using this method, the radius of influence of the dissolved oxygen from the sparge well was estimated to be about 24 feet ' Since positive pressure was exerted on only available one well (OB-3) other than the air sparge well, it is difficult to calculate a radius of influence for free air in the vadose zone subsurface Additionally, pressures on OB-3 varied between 0 7 and 25 inches of water while the pressure at the sparge well remained unchanged Therefore, the data from OB-3 was not constant enough to suggest that there was a relationship between pressure and flow applied at ASW-1 and pressure measured at 013-3 7.4 Discussion of ORC Boring Field Results ' Oxygen measurements were made during the conduct of the pilot test and on a monthly basis (for 6 months) from monitoring well MW-6 to determine if dissolved oxygen from ' the ORC boring was entering the well at measurable levels The most recent measurement was completed on July 20, 2000, but to date, no increase in dissolved oxygen has been noted in MW-6 as a result of the ORC material The ORC boring is 2937 Veneman Ave, #B240 Geo-Phase Environmental inc Phone(209) 569-0293 Modesto, CA 95356 Fax(209) 569-0295