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' Atlantic Richfield Company 3
<br /> ARCO 595,6100 North Highway 99,Stockton,CA December 11,2001
<br /> • TPHg, BTEX, MtBE, and fuel oxygenates were reported as nondetectable in soil samples
<br />' with the exception of trace detections of benzene, toluene, and xylenes in MW-5 at
<br /> depths of 15, 25, and 55 feet bgs Soil analytical results are presented in Table 4 Field
<br /> and laboratory procedures are presented as Attachment D Certified analytical reports
<br />' and chain-of-custody documentation are presented as Attachment E
<br />' Depth Discrete Groundwater "Grab" Samples
<br /> Depth discrete groundwater"grab" samples were collected from boring PSB-1 at depths
<br />' of 75 and 90 feet bgs, and from PSB-2 at depths of 64, 75, and 95 feet bgs The work
<br /> plan indicated that water samples would be collected at depths of 75, 90, and 100 feet
<br /> However, during drilling activities water producing zones were located at 75 and 95 feet
<br />' in PSB-1 and 64,75,and 100 feet in PSB-2 Depth discrete samples were collected using
<br /> the hydropunch sampling method In a separately cored boring that was backfilled with
<br />' grout upon completion The groundwater samples were analyzed for TPHg, BTEX, and
<br /> MtBE using EPA Methods 8015 (modified)/8020, and fuel oxygenates TBA, MtBE,
<br /> DIPE, ELBE, TAME, 1,2-DCA, EDB, and ethanol (selected samples) using EPA Method
<br />' 8260A/B
<br /> MtBE and 1,2-DCA were reported in PSB-1 at depths of 75 feet bgs and 90 feet bgs
<br /> MtBE and 1,2-DCA concentrations in the sample collected at 90 feet bgs were 39 ppb
<br /> and 10 ppb, respectively MtBE and 1,2-DCA were reported In PSB-2 at depths of 64
<br /> feet bgs and 95 feet bgs MtBE and 1,2-DCA concentrations to the sample collected at
<br />' 95 feet bgs were 2 7 ppb and 4 2 ppb, respectively Additionally, the groundwater
<br /> sample from PSB-2 at 95 feet bgs contained minor detections of toluene (1 0 ppb), ethyl-
<br /> benzene (0 54 ppb), and xylenes (3 0 ppb) Groundwater"grab" sample analytical data
<br />' is included in Table 5
<br /> Groundwater Monitoring Well Development, Sampling, and Surveying
<br />' On July 30, 2001, the groundwater monitoring wells were developed by rigorously
<br /> surging over the length of the screen interval and by purging approximately ten casing
<br />' volumes of water
<br /> Groundwater samples were collected from the existing and newly installed groundwater
<br />' monitoring wells on August 1, 2001 Samples were analyzed for the presence of TPHg,
<br /> BTEX, and MtBE using EPA Methods 8015 (modified)/8020, and fuel oxygenates TBA,
<br /> MtBE, DIPE, EtBE, TAME, 1,2-DCA, and EDB using EPA Method 8260A
<br />' MtBE was reported at concentrations of 2 6 ppb (MW-5) and 94 ppb (MW-7) in the
<br /> newly installed wells 1,2-DCA was reported at concentrations of 3 2 ppb (MW-5) and
<br /> 23 ppb (MW-7) All other analytes in the new wells were reported as nondetectable
<br /> . The highest hydrocarbon concentrations in the existing wells were generally reported in
<br /> well MW-4 Groundwater analytical data is presented in Tables 1 and 2, and is
<br />' illustrated on Figure 5 Field and laboratory procedures are presented as Attachment D
<br /> I077 43029 330/well msta112 doe
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