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C'M10glcal Tec/ucla I= Page 12 Dual Phase Extraction Pilot Test Report Project No 662 2 February 22,2005 ' 5.3 Geology and Contaminant Distribution MW-5 &MW-6 The following paragraphs will discuss the geology of the two new boreholes and the contaminant distribution of their associated soil samples ' The MW-5 boring consists of alternating layers of sands, silts and clays (refer to boring log in Appendix B) ' ❑ The silt units are less than five feet in thickness and occur at 5 and 15 feet bgs The silts are grey in color, firm and moist The shallow silt contained white CaCO3 ' nodules,root tubes, some iron oxide staining ❑ Sand units were encountered at depths of 10, 20, 25, 30, and 35 feet bgs The sands ranged from It grey to brown in color, very fine to very coarse in size, firm to loose ' and arkosic in origin Sands at 20 and 30 feet contained significant clay and silt respectively, and some iron oxide staining was noted in the 35 feet bgs sample u A clay unit was encountered at 16 feet bgs This layer was less than 3 feet thick, grey ' in color, firm and moist o Significant gravels were present at 40 and 45 feet bgs The pebbles ranged from 5 — 10 mm in size, with fine to very coarse sand grains present The gravels are grey, wet and loose A notable occurrence was the presence of a black charcoal smear on the removed auger bit between the 40 and 45 foot depth ' Boring MW-5 was placed adjacent to CPT-7 The CPT log for CPT-7 is included in Appendix B and a comparison of the MW-5 log to the CPT borehole reveals only a fair correlation The CPT boring has more variability due to the continuous logging versus the ' five foot interval used in MW-5 One strong correlation is the coarse gravel/sands present from 38 -- 46 feet bgs This interval is believed to be a preferential pathway for off site contaminant transport Well MW-5's screened interval of 40 - 45 feet bgs intercepts this ' zone The MW-6 boring consists of alternating layers of sands, silts and clays (refer to boring log in ' Appendix B) a Sand units were encountered at depths of 5, 10, 25, 30, 35 and 40 feet bgs The sands ' ranged from It to dark, or brown in color, very fine to very coarse in size, firm to hard and arkosic in origin Sands at 30 feet contained clayey fraction, discontinuous root ' tubes, brown root material and a faint hydrogen sulfide odor ❑ Clay units were encountered at 15, 20 and 45 feet bgs The 15 feet bgs sample was grey, slightly moist, firm to hard and contained significant silt The 20 feet bgs. ' sample was more uniform without the silt fraction The clay unit at 45 feet contained very fine sand nodules, approximately 1/4" in diameter • ❑ The sands at 35 to 40 feet bgs were coarse grained but did not contain the distinct ' gravels noted in MW-5 at these depths