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r <br /> Mr. Kyle Christie <br /> February 23, 1989 <br /> Page 4 <br /> i <br /> Field Methods <br /> Prior to sample collection, groundwater was purged by pumping from each monitoring well <br /> by Armour Petroleum, Inc., of Fairfield, California. The pH and specific conductance of the <br /> »r discharged water were monitored. Three well volumes of groundwat„r(ane well volume being <br /> the volume of water inside the well casing plus 35 percent of the gravel packed annular space) <br /> ' were svacuated from monitoring wells W-2, W-213, W-3, W-5, W-6, and W-7. The low <br /> groundwater level in January 1989 (see Figure 2) made purging difficult in monitoring wells <br /> W-1, W-2A, and W-4. Due to slow recharge.of groundwater into monitoring wells W-1, <br /> W-2A and W-4, 0.5, 1.2, and 0.75 well volumes, respectively, were evacuated from these <br /> wells. <br /> s <br /> Each well was sampled with a Teflon bailer equipped with a bottom-emptying valve. The <br /> sample was drained directly from the bottom valve into two 40-milliliter glass bottles with <br /> Teflon-lined septums. The samples were store, on ice from the time of collection through <br /> delivery to Eureka Laboratories Inc., in Sacramento. All purging and sampling equipment was <br /> �°- washed with laboratory-grade L.etergent and tap water thea rinsed with deionized water before <br /> each use. All groundwater produced during purging and sampling was disposed of by Armour <br /> Petroleum, Inc. <br /> January 1989 Field and Analytical Results <br /> r Groundwater levels were measured at approximately 49 feet below ground surface in April <br /> 1987, when the first three monitoring wells were installed. Water level measurements show <br /> that groundwater dropped to approximately 55 feet below ground surface in October 1987 and <br /> rose to approximately 52 feet below ground surface in March 1988. Groundwater levels were <br /> { measured at approximately 59 feet below ground surface in late September 1988. By January <br /> 1989, groundwater levels had risen to approximately 57 feet below ground surface. In January <br /> f. <br /> 1989, groundwater flow direction was to the southeast under a hydraulic gradient of about 11 <br /> k I feet per mile (0.2 percent). <br /> r Dissolved BETX concentrations in <br /> s r� groundwater samples collec'rd from April 1957 through <br /> January 1989 are summarized in Table 1. January 1989 benzene concentrations are shown on <br /> 3 Figure 1. Complete laboratory reports of the January 1989 groundwater sample analyses are <br /> ;y5 enclosed as Exhibit A. January 1189 analytical results show benzene concentrations in <br /> groundwater in on-site monitoring wells W-1, W-2, W-2A, and W-3 are greater than California <br /> a Department of Health Services' (DHS) action levels. DHS action levels for BETX are 0.7 <br /> arts per billion P p (ppb), 680 ppb, 100 ppb, and 624 ppb, respectively. Ethylbenzene was <br /> identified at concentrations below the DHS action level in on-site monitoring wells W-1, W-2, <br /> `-1 W-2A, and W-3__Toluene_concentrations_in_groundwater.,in-on-site monitoring-wells-W=1, - -- - - --- - <br /> W-2, W-2A, and W-3 are greater than the DHS action 'level. Xylene was identified in <br /> concentrations greater than the DHS action level in on-site monitoring wells W-I, W-2, and <br /> W-3, and at a concentration less than the DHS action level in monitoring well W-2A. <br /> ` BROWN AND CALDWELL . <br /> t ` - <br /> 723 8 STREET SACAAA CCM GAUFMNN W14-70W•(916)444-0123 <br />