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r <br /> Nlr. Kyle Christie <br /> klay 25, 1989 <br /> Page 4 <br /> Field Melhods <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 <br /> the discharged water were monitored. Three well volumes of groundwater (one well <br /> -- volume being the volume of water inside the well casing plus 35 percent of the gravel <br /> packed annular space) were evacuated from monitoring wells W-2, W-3, W-4, W-5, W-6, <br /> and W-7. The groundwater level in April 1989 (see Figure 2) made purging difficult in <br /> monitoring wells W-1 and W-2A. Dupe to slow recharge of groundwater into monitoring <br /> well W-1, W-2A, and W-2B, 0.7, 2.3, and 2.3 well volumes, respectively, were evacuated <br /> from these wells. <br /> Each well was sampled with a Teflon baiter quipped with a bottom-emptying valve. The <br /> santp:�t was drained directly from the bottom vaive into two 40-milliliter glass bottles with <br /> Teflon-.fined septums. The samples were stored on ice from the time of collection through <br /> delivery to Eureka Laboratories Inc., in Sacramento. All purging, and sampling equipment <br /> -' <br /> was washed with laboratory-grade detergent and tap :eater then rinsed with deinized water <br /> before each use. All groundwater produced during purging and sampling was disposed of <br /> by Armour Petroleum, Inc. <br /> r1 January 1989 Field and Analytical Respits <br /> } '•_J Groundwater levels were measured at approximately 49 feet below <br /> ground surface in April <br /> 1987, when the first three monitoring wells were installed. Water level measurements <br /> s show that groundwater dropped to approximately 55 feei below ground surface in October <br /> + I987 and rose to approximately 52 feet below ground surface in March 1988. <br /> Groundwater levels were measured at approximately 59 feet below ground surface in late <br /> September 1985. By April 1989, groundwater levels had risen to approximately 55 feet <br /> F t« below ground surface. In April 1989,:groundwater flow direction was to tl:e south under a <br /> hydraulic gradient of about I4 feet per mile (0.3 percent), <br /> Dissolved'BETX concentrations in groundwater samples collected rrom April 087 through <br /> i. January 1989 are summarized in Table 1. ApriI 1989 benzene concentrations are shown on <br /> Figure 1. Complete laboratory reports of the April 1989 groundwater sample analyses are <br /> enclosed as Exhibit A. April 1989 analytical results srF:w benzene concentrations in <br /> groundwater in on-site monitoring wells W-1, W-2, W-2A, and W-3 are greater than r <br /> California Department of Health Services' (DHS) action levels. DHS action levels for <br /> y„ BETX are 0.7 partsper billion (ppb), 680 ppb, 100 ppb, and 620 ppb, respectively. <br /> Toluene concentrations in groundwater in on-site monitoring well W-1 is greater than the <br /> t DHS action level. Xylene was ides tificd in concentrations greater than the DHS action <br /> level_ in-on-site <br /> _monitoring-wells--W-1;-W-'2,-and-W-3.- — <br /> .,� BETX were not detected in groundwater in monitoring well W-2B. Monitoring well W-2B <br /> is the deepest monitoring well on site.and is accessible •o.grountiwater in the 74- to 88- <br /> f6ot depth interval (see Figure 2). <br /> i <br /> BROWN AND CALDWEI.I_ <br /> ` 7233 VREEr SACPAMENI4,CA 95811•(916J iJ1.p123 <br /> �,: - - <br />