ARCHIVED REPORTS_XR0002811 - Laserfiche WebLink

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2,0 GROUNDWATER MONITORING, SAMPLING AND ANALYSIS On February 18, 1999, Ramage Environmental monitored and sampled groundwater at the site 2,1 Groundwater Mon,tormg Depth-to-groundwater measurements were taken in six of the nine groundwater monitoring wells to evaluate groundwater flow and gradient characteristics Depth-to-groundwater measurements ' were not taken from MW-1 and the two deep soil vapor extraction wells (VW-1 and VW-2) because the surveyed elevations of these wellheads was compromised during connection to the sod vapor extraction and air sparging system The depth-to-groundwater beneath the site ranged from 35 71 feet below ground surface (bgs) in MW-4 to 39 38 feet bgs in MW-7 MW-7 is completed above-grade and protected with a monument casing The groundwater elevation beneath the site ranged from a high of 21 03 feet below mean sea level (MSL) in MW-3 to a low of 21 14 feet below MSL in MW-7 Groundwater levels have risen an average of 2 79 feet since groundwater levels were last measured on November 5, 1998 In the past year, groundwater levels have risen an average of 6 35 feet Since May 1992, the groundwater levels have risen an average of 28 17 feet The historical groundwater monitoring data are summarized in Table 1 The groundwater flow direction and gradient are illustrated on the groundwater surface map (Figure 3) The groundwater gradient was calculated at 0 001 foot/foot in a northeasterly direction This result is consistent with historical groundwater flow and gradient data 22 Groundwater Sampling and Analysis Groundwater from MW-6, MW-7 and the two deep soil vapor extraction wells (VW-1 and VW-2) was sampled to evaluate the concentration of gasoline hydrocarbons at the groundwater table The groundwater monitoring wells (MW-1, MW-2, MW-3, MW-4 and MW-5) were not sampled because of groundwater levels significantly above the screened interval of these wells Each of the four wells (MW-6, MW-7, VW-1 and VW-2) was purged using a decontaminated bailer of at least three well volumes and/or until pH, temperature and electrical conductivity values had stabilized Fallowing purging, groundwater samples were collected from the four 3