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TPHD,with one relatively elevated level of 33,000 micrograms per liter(ug/1)TPHD in B-2 in a <br /> downgradient location. BTEX, MTBE and related oxygenates were not revealed in any <br /> groundwater sample. <br /> Wright drilled and sampled five (5) additional borings (B-5, B-6, B-7, B-8 and B-9) in October <br /> 2008. Soil and groundwater samples were collected and analyzed only for TPHD since previous <br /> analysis had shown that gasoline and related fuel compounds had not been detected. TPHD <br /> dissolved concentrations were relatively low in groundwater. Boring B-6 drilled adjacent to <br /> Boring B-2 showed only 170 Ug/l (compared to 33,000 Ug/l at B-2 in 2003) a significant <br /> decrease. The laboratory reported that the TPHD was higher boiling than typical diesel fuel. In <br /> our opinion a large contaminant problem is not indicated from this data, and only a small <br /> dissolved residual and possibly degraded TPHD plume is present. <br /> On the basis of a data review and discussions with staff, PHS/EHD requested that one (1) <br /> groundwater monitoring well be installed near Wright boring B-5. This new well is used in <br /> conjunction nearby existing WWTP groundwater monitoring wells MWHP-5, MWHP-6, <br /> MWHP-7 and MWHP-8 installed by CH2M Hill for groundwater direction plots (see Figures 1 <br /> and 2). It is our understanding from a limited review of the existing CH2M Hill wells that they <br /> are screened in the same aquifer strata as that investigated in the area of the proposed new <br /> monitoring well by Wright in 2003 and 2008. The new well was designated "MWWES-1" to <br /> avoid confusion between this monitoring well and the existing CH2M Hill monitoring wells. <br /> The CH2M Hill wells (MV4IP-5, MWHP-6, MWHP-7 and NIWHP-8) for water level <br /> measurements only. These measurement data will be used to plot groundwater flow contours <br /> together with new well MWWES-1. The new well was sampled for both water level <br /> measurement and chemical analysis program discussed below. The existing CH2M Hill wells <br /> are not sampled for groundwater quality for this Wright study. <br /> Scope of Work <br /> 2.0 Field Methods—Drilling and Sampling Exploratory Boring <br /> One (1) exploratory boring was drilled at the location shown on Figure 2. Drilling and well <br /> installation permits were secured from the SJC/EHD, and an underground utility clearance was <br /> performed prior to doing the fieldwork together with a site safety plan. <br /> The borehole was drilled with a truck-mounted hollow-stem auger rig. All drilling equipment <br /> and sampling tools was cleaned prior to arriving, and before leaving the site. The <br /> decontamination process used a tri-phosphate soap to wash the soil sampler,between each sample <br /> run. Augers and drill rods were decontaminated in similar fashion between each borehole using <br /> a pressure washer to clean and remove soil/sediment adhering to the augers, rods and drill bits. <br /> The hollow-stem augers were advanced and discrete soil samples were collected for lithology <br /> logging at five-foot intervals of depth from each borehole. The augers and drill rod were <br /> advanced to the desired sampling depth interval, and a drive split spoon sampler was driven <br /> ahead of the drill bit. <br /> Page 2 of 9 <br />