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i C---------- LEARWATER G R O U P ! N C £rtniranmertta! Sernacrs VW-1, VW-2, MW-4, and MW-7 exhibited vacuums varying from 0 03 to 0 25 in w c , while the remaining observation wells RW-1, MW-1, MW-5, and MW-6 still exhibited pressures ranging from 0 25 to 6.00 in w c Although the sparge vapors could not be completely controlled by extracting soil vapor solely from VW-3, it is likely that they could be controlled by a grid of operative vapor extraction points (z e concurrent vapor extraction from VW-1, VW-2, VW-3, and RW-1) Dissolved oxygen measurements taken at the end of the sparge test are compared with initial dissolved oxygen measurement in Table 6 Initial measurements indicate depleted levels of dissolved oxygen (<2 0 mg/L) across the site The most depleted wells (<0 5 mg/L) were RW-1 and MW-2, located in the center of the dissolved plume After the sparge test, dissolved oxygen levels had increased significantly in wells RW-1, MW-5, MW-6, and SW-1, indicating a radius of influence of approximately 50 feet Dissolved oxygen measurements collected before and after the sparge test are presented graphically on Figure 10 Groundwater elevations measured at the end of the sparge test were compared with static water levels to assess the effect spargmg might have on groundwater flow Water levels rose in some wells and fell in others by the end of the test, and the resulting groundwater table contour was different than the static water table measured previously Prior to sparging, groundwater flow was toward the northeast at a hydraulic gradient of 0 0019 After sparging, groundwater flow was toward northwest and the hydraulic gradient had increased to 0 0028 Groundwater elevation contours before and after the sparge test are shown on Figure 11 Analytical results of air samples from VW-3 collected during the sparge test are compared with results from the vapor extraction test (pre-sparge) in Table 4 The results for VW-3 show slightly lower concentrations of hydrocarbons in extracted vapor during sparging Given the increase in dissolved oxygen in surrounding monitoring wells, one would expect the hydrocarbon concentrations in vapors extracted from VW-3 during sparging to be greater than concentrations measured during the vapor extraction test as dissolved hydrocarbons are volatilized by the sparge A lower hydrocarbon concentration probably reflects the fact that (contaminated soil one pore volume had not yet been extracted and initially high hydrocarbons concentrations in extracted vapor continued to decline despite the addition of hydrocarbons volatilized by sparge air. Certified analytical reports are presented in Appendix B If sparging is used in the future as a remedial technology, the potential sparging has to mound groundwater, and spread contaminants, could probably be effectively • mitigated by groundwater extraction from one or more recovery wells. D-107,PAR/RAP 14 lune 11, 1996