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1 '17 r!A r 30 May 1997r .AGE-NC Project No 95-0121 FI { Page 2 of 4 - 2 2 ! GROUND WATER SAMPLE COLLECTION Monitoring wells MW-1 through MW-9 were allowed to recover for a minimum of one hour pirior 1 to.sample collection Water samples were collected from wells-MW-I'through MW-9 utilizing dedicated, disposable polyethylene bailers and new nylon rope Samples were collected in one-liter amber bottles and 40-m1 EPA-approved VOA vials containing 0 5 ml 18% hydrochloric acid as a I preservative Care was taken to ensure that visible air bubbles were not present in the VOAs after ' filling and capping Ground water sample containers were labeled with the well designation, date t time, and the sampler's initials r n fl 2,3 , LABORATORY ANALYSIS OF GROUND WATER SAMPLES l. Each ground water sample was logged onxa chain-of-custody form, placed in a chilled container and y transported to a California state-certified laboratory for analysis The samples were analyzed in r ' ,accordance with EPA Method 8015-M for total petroleum hydrocarbons quantified as gasoline and modified for diesel (TPH-g and TPH-d), and in accordance with EPA Method 8020 for volatiles aromatics (benzene, toluene, ethyl benzene and xylenes BTE&X),and methyl tert-butyl ether (MTBE) The laboratory report (Castle-Analytical Laboratory Reference No 1029) and';chain-of- custody forms are presented in Appendix B ' I 3.0 FINDINGS ' 3 1 y `RELATIVE GROUND WATER ELEVATION'AND GRADIENT T ( � I ' The depths to ground water in wells MW-1 through MW-9 ranged between 17 05 and 19 12 feet _ below the top of well casings Between November 1996 and February 1997, ground water depth decreased at the site an average of 3 70 feet at,thersite The ground water-ell evatian data for, MW-I though 9 are in Figure 3 - Relative Ground Water Elevation Map q ' Dunng the February 1997 monitoring event,`ground water was between five and'fifteen feet above ' the screened intervals in�nomtonng wells MW-1 through MW-9 Therefore, the wells are "drowned", s ' 'and may not be fully representative of ground water condition`s near the top of the saturated zone, where fuel hydrocarbons would be,expected to`have the greatest impact In November 1996, the gradient was calci_ilated to be 0 0025 ft/ft or approximately I4 feet per mile, , directed'approximately N 04,°E In February"1997, the gradient was calculated to be 0 0016 ft/ft or approximately 9 feet per bmile, directed approximately N� 64,E Between November I996 and February 1997, ground water flow direction beneath the site rotated approximately 60° from north 1 - to east i ' R r r s 1 r + s I �