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e <br /> A <br /> J� <br /> 1 ' <br /> A <br /> di <br /> C7 _ <br /> hV <br /> Chevron/Airport 12 <br /> Feb-uary 1991 <br /> Table 3. Well Survey and Monitoring Data <br /> for January 24,1991 (in feet) <br /> well Time Wellhead Elevation Depth-To- Hydrostatic <br /> No. (mean sea level datum) Water(feet) Elevation <br /> k <br /> MW-1 11:30 18.60 54.96 — 36.36 <br /> ~ <br /> MW-2 11.22 16.66 53.16 — 36•48 <br /> MW-3 11:25 17.36 53.89 — 36.53 <br /> MW-4 11:10 16.70 53.05 — 36.38 <br /> Groundwater samples were collected on December 3, 1990,from MW-i,MW-2 and MW-3,after <br /> well development and bailing(M-1). A groundwater sample was collected from monitoring well MW-4 <br /> on January 24, 1991. The wells were given time to recover to at least go percent of their original static <br /> water volume before sampling. This procedure allows for the collection of representative groundwater <br /> samples. The purged water was collected and stored on site with the development water In 55-ga11on <br /> drums pending proper disposal. <br /> E s After the wells had adequately recharged,groundwater samples were collected with an <br /> EPA-approved disposable sampler. Groundwater samples to be analyzed for the preser ice o; <br /> r concentrations of BTEX and TPH-as-gasoline were placed In 40 milliliter(mi)glass vials,acidified to <br /> ER Ali samples were labeled,placed on Ica in <br /> ensure a pH below 2.0,then sealed with Teflon septa caps. <br /> I ° an insulated cooler and transported under l)i-iain-cf-Custody Manifest to the Suparior Analytical <br /> $ Laboratory In Martinez,California. <br /> h� <br /> SUBSURFACE CONDITIONS <br /> SOILS <br /> '^' The subsurface materials encountered during this Investigation consisted primarily of a thick unit <br /> I � (up to 50-feet-thick)of Interbedded brown clayey silts and silty clays and overlying lenses of sand and <br /> j44 gravel. The water-bearing zone occurs In the sands and gravels and appears to be unconfined. <br /> Figure 5 presents a cross section of the lolls which were encountered. As Is noted In the boring logs <br /> . a <br /> (Appendix i3),geld screening with a PID showed no detectable concentrations of volatile o.rganlo vapors. 1 <br /> r� <br /> �__if� kPt('ifIQUNDWATER <br /> �TF:CHN0110GY,INC. <br /> a 3 <br />