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<br /> First Quarter 1998 Monitoring and Sampling Report
<br /> The Southland on Store#20304 455 Grant Line Rd.,-Trfty,CA April 10,19 B
<br /> Prior to purging,dissolved oxygen levels were recorded in each well using a CHEMetrics colorimetric
<br /> dissolved oxygen analysis kit No.C-7512. Dissolved oxygen data taken from five monitoring wells on
<br /> February 25, 1998 indicate depletion of oxygen through intrinsic biodegradation in well MW-5,while in wells
<br /> MWS,MW-8,MW-9 and MW-10 dissolved oxygen levels are relatively high, possibly due to fresh water
<br /> recharge from recent rains. Dissolved oxygen levels ranged from 1 milligrams per liter(mg/L)in well MW-1
<br /> to 4 mg/L in wells MW-8 and MW-9. Generally,in the center of the plume and near the downgradient edge
<br /> of the plume,dissolved oxygen levels are low,indicating oxygen depletion. Dissolved oxygen data for wells
<br /> a..
<br /> monitored on February 25, 1998 are presented in Table 1.
<br /> Monitoring Well Sampling and Analytical Results
<br /> Groundwater samples were collected from wells MW-4,MW-5,MW-8,MW-9,and MW 10. Before
<br /> sampling,at least four well-casing volumes of groundwater was removed from each monitoring well, unless
<br /> i6, the well was purged dry. Field measurements of temperature,conductivity,dissolved oxygen (D.O.),and
<br /> pH were recorded during well purging. The groundwater samples were collected using disposable bailers
<br /> and placed in analysis-specific sample containers with analysis-specific preservatives. The samples were
<br /> then sealed and labeled with the job identification number,the sample number,date,time,and type of
<br /> laboratory analysis required. The samples were stored on ice in an insulated container and transported
<br /> under chain-of-custody manifest to Core Analytical Laboratory,in Anaheim, California. The groundwater
<br /> +- samples were analyzed for BTEX,MTBE and TPH-G using Environmental Protection Agency(EPA)
<br /> methods 8020/modified 8015,and for oxygenates:MTBE,TBA, DIPE, ETBE,and TAME using EPA method
<br /> 8260. Groundwater purged during the first quarter monitoring and sampling event was pumped through the
<br /> groundwater extraction system.
<br /> Dissolved benzene and TPH-G were detected in groundwater samples from monitoring wells MW-8,MW-9
<br /> and MW-1 0 with highest concentrations reported in MW 10 at 5,200 micrograms per liter(pg/L) and 30,000
<br /> pg/L, respectively(Figure 3). Using EPA method 8260,dissolved MTBE was not reported in any well above
<br /> detection limits. TBA, DIPE, ETBE, and TAME were not detected in any wells. Analytical results from the
<br /> groundwater samples collected on February 25, 1998 are presented in Table 1,and historical analytical
<br /> results are summarized in Table 1A. The laboratory analytical reports and the chain-of-custody records for
<br /> this sampling event are included in Attachment 4.
<br /> Graphs of benzene versus water table elevation (WTE)are presented in Figures 4 through 7
<br /> (Attachment 1).These graphs indicate an inconsistent relationship between benzene and WTE,in MW-1
<br /> there appears to be a direct relationship,while in MW-10 an inverse relationship is apparent.
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<br /> �. FLUOR DANIEL GTI
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