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22 March 1999 <br /> • AGE-NC Project No 95-0144 <br /> Page 3 of 5 <br /> below a clay layer Ground water elevation decreased an average of 103 feet in the remaining wells <br /> ' The approximate hydraulic gradient for the February 1999 monitoring event was calculated to be <br /> 0 003 ft/ft with a northerly flow direction Ground water elevation contours denved from data <br /> ' collected on 02 February 1999 are depicted in Figure 3 Ground water was between 0 8 and 6 2 feet <br /> above the screened interval in monitoring wells MW-1 through MW-18 Groundwater was witlun <br /> the screened intervals of MW-19A, MW-20A and MW-21A <br /> ' Ground water elevations in wells MW-19, MW-20 and MW-21 were between 16 and 19 feet lower <br /> in the lower screened intervals beneath the confining clay layer than in the upper screened interval <br /> Data from the upper screened interval, established in first-encountered ground water was used for <br /> gradient determination <br /> ' 3 2 ANALYTICAL RESULTS OF WATER SAMPLES <br /> ' During the November 1998 monitoring,TPH-g was detected in monitoring wells MW-13,MW-21A <br /> and MW-21B at concentrations of 53 parts per billion(ppb,reported as micrograms per liter), 3,200 <br /> lieppb and 2,200 ppb,respectively BTEX were detected in MW-21A and MW-21 B at concentrations <br /> as high as 170 ppb (benzene, MW-21A) Toluene was also detected in MW-1 and MW-19B at <br /> concentrations of 0 53 ppb and 0 78 ppb, respectively Xylenes were detected in MW-19B at a <br /> ' concentration of 0 72 ppb TPH-d was detected in wells MW-1,MW-13, MW-19A,MW-1913,MW- <br /> 20A,MW-20B,MW-21A and MW-21B at concentrations ranging from 65 ppb to 18,000 ppb TPH- <br /> mo was detected in samples collected from MW-21A and MW-21B at concentrations of 1,200 ppb <br /> ' and 320 ppb, respectively Other petroleum hydrocarbons were not detected at the site during the <br /> November 1998 monitoring event Analytical results for November 1998 are summarized on Table <br /> 2 <br /> ' Dunn the February 1999 sampling event, TPH- was detected in monitoring wells MW-21A and <br /> During P g g <br /> MW-21B at concentrations of 4,200 ppb and 1,300 ppb, respectively Benzene, ethylbenzene and <br /> ' xylenes were detected in MW-21A and MW-21B at concentrations as high as 240 ppb (benzene, <br /> MW-21 A) Toluene was detected in MW-1, MW2, MW 12 and MW-20B at concentrations ranging <br /> ' from 0 57 to 0 71 ppb TPH-d was detected in wells MW-13, MW-19A, MW-1913, MW-20A, MW- <br /> 20B, MW-21A and MW-21B at concentrations ranging from 57 ppb to 6,500 ppb TPH-mo was <br /> detected in the sample collected from MW-21A at a concentration of 500 ppb Other petroleum <br /> hydrocarbons were not detected at the site during the February 1999 monitoring event Analytical <br /> results for February 1999 are summarized on Table 3 Analytical results of historical ground water <br /> samples are summarized on Table 4 <br /> ' Duringthe November 1998 sampling event, MTBE was detected b EPA Method 8260m in MW- <br /> 19B <br /> P g Y <br /> 19B at a concentration of 14 ppb Other oxygenated compounds were not detected at the site <br /> ' Advanced GeoEnvlronmentel.Inc <br /> 1 <br />