ARCHIVED REPORTS XR0000065 - Laserfiche WebLink

Home Browse Search

. Mr Martin Harris April 18, 2001 Page 4 of 6 noted at samples collected from 15 or 20 feet bgs FID readings from boring MW1 generally diminished with depth, ranging from 138 parts per million (ppm) at a depth of 5 feet bgs to 2 ppm at a depth of 15 feet bgs, and 3 ppm at 20 feet bgs No petroleum odors were noted in any sample collected from borings MW2 through MW4 FID readings from these bonngs were all zero Boring logs and well construction details are included in Attachment A Groundwater was first encountered at depths ranging from approximately 7 feet bgs in boring MM2 to 9 feet bgs in boring MW3 To determine the groundwater elevation, the static depth to groundwater was measured in each well and subtracted from the surveyed wellhead elevation The potentiometnc surface ranged from 18 36 to 18 42 feet above mean sea level Based upon these data, groundwater flows in a westerly direction with a hydraulic gradient of approximately 0 0013 ft/ft, or approximately 7 feet per mile Groundwater elevations are summarized in Table 3 A potentiometnc surface map generated using the January 23, 2001 well monitoring data is depicted on Figure 3 Groundwater monitoring and purge logs are included in Attachment B 3.2 Soil Analytical Results Although no evidence of any soil contamination was noted in bonngs MM2, MM3, or MW4, soil samples collected at depths of 10 and 20 feet bgs from these borings were analyzed to confirm the absence of contamination Due to field evidence of contamination in boring MMI, however, all soil samples collected from boring MMI were analyzed for gasoline constituents TPHg was detected at a concentration of 22 ppm in boring MMI at a depth of five feet bgs, although no BTEX constituents or MTBE was detected It should be noted, however, that detection limits for these constituents were elevated due to dilution factors No gasoline constituents, including MTBE or benzene, were detected in any other soil samples analyzed from borings MW 1-MW4 In addition, no gasoline constituents were detected in a 4 1 composite sample collected from the stockpiled soil Soil analytical results are summarized in Table 1 Laboratory reports and chain of custody documentation are included in Attachment C 3.3 Groundwater Analytical Results Low levels of gasoline constituents were detected in each site well TPHg was detected in wells MW 1 and MW2 at concentrations of 730 parts per billion (ppb) and 110 ppb, respectively Xylenes were also detected in wells MW1 and MW2 at concentrations of 21 and 0 8 ppb, respectively Benzene (1 6 ppb), toluene (1 3 ppb), and ethylbenzene (18 ppb) were detected only in well MW1 No TPHg or BTEX were detected in either well MW3 or MW4 However, MTBE was detected in each well, ranging from 16 ppb in cross-gradient well MM4 to 2 5 ppb in well downgradient well MW3 Groundwater analytical results are summarized in Table 2 Laboratory reports and chain of custody documentation are included in Attachment C 4.o SUMMARY • . Four groundwater monitoring wells (MW1-MW4) were installed to a depth of approximately G 1Data1GROUNDZE1TufiBoy\Reports\WELLRPT doc