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16 <br /> 28 April 1995 <br /> AGE-NC-95-0112 <br /> rPage 3 of 4 <br />' 4.2. GROUND WATER SAMPLE COLLECTION <br /> Water samples were collected from Ni NN'-1, MW-4, NII-5, MW-6, NIW-7 and NMI-& <br /> Additionally, three ground water salllpies \were collected front purge water stored on site ill <br /> 55-gallon drums. All samples \vere collected using new disposable plastic bailers. The <br /> samples were collected in 40-nil EPA vials, placed ill a chilled container, and transported <br /> ' under chain-of-custody to Alplia Analytical Laboratories (AAL) in Ukiah, California. A11 <br /> samples were analyzed for total petroleum hydl'ocalbons as gasoline (FPI-I-g} and at'onlatic <br /> hydrocarbons (BTE,CX) in accordance with EPA methods 5030/50151n and 602, respectively. <br /> 5.0. FINDINGS <br /> 5.1. GROUND NATER ELEVATION AND GRADIENT <br /> The relative elevation of the around water ill each \\•ell was calculated by subtracting tile <br /> around wafer cleptll fro111 the sull,eyed casing elevation (Table 1). Ground \eater elevation <br /> has risen all average of 2.6 feet since the October 199 monitoring event. 1-Io\\C\'e r, <br /> 1110111tor113a \"ells �1��'-2 and i\11V-3 rerllain cli;. 1-11e flow direction of ground water also <br /> reillains to the south at a similar overall gradient to the gradient obsel�ed thouohout 1994 <br /> (Figure 3). A slight mounding effect is still present near MW-1: <br /> 7 5.2. LABORATORY ANALYSIS OF GROUND WATER SAMPLES <br /> PetroIeulll hydrocarbons were not detected in samples frons MW-6 or MW-S. TPI-1_o was <br /> detected ill saniples from N'1W-1 and N11W-4 at concentrations of 42,000 and 370pg/l (parts <br /> per billion: ppb), respectively. BTE&X were also detected in the same samples at <br /> collcentl-atlons up to 6,600 ppb. Toluene was detected in NIW-5 at 0.33 ppb and sample <br /> ' fl-oln MW-7 inclicated the detection of benzene and x}1enes at 2.1 and 3.7, respectively. The <br /> analytical results of current and previous water samplesummar <br /> are sized ill Table 2. The <br /> curreut laboratory report and chaill-of-custody are included ill Appendix B. <br /> 6.0. CONCLUSIONS <br /> G.1, HYDROCARBON IMPACTED GROUND WATER <br /> ' G1'ouncI \eater flow direction leas been collsistently south/southwest Since the installation of <br /> MW-6 through MW-8 in April 1993. The rise of water table is attributed to the excessively <br /> ically resulting in. n1Qre elevated <br /> Iligll precipitation rate of the receltt Wet season, typ <br />