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t G14�0�(j'�CkJIfC'.P�11� Revised Site Conceptual Model Report Page 6 ] Project No.507.2' April 3,2008L C, Bonn s SB-6 MW-7 MW-10 and MW-109: • The geology of the site was field logged as predominately clays and sandy clays with lesser amounts of silts and sands. The clays range from brown to blue-green, and contained varying amounts of carbonate nodules black staining organic materials and iron oxide • The clayey soils in the upper 20 ft of MW-109 contained prominent field evidence of k 11 contamination- odor and staining. The 80-foot hydrocarbon odor, and the OVMdetected 19 arts sample in MW-109 had a faint • p per million organic vapors. } The deeper soil encountered in';SB-109 was a blue/grey to blue/green color so it was difficult to visually determine when drilling had progressed past the contamination. Bo ig SB-7 . The subsurface ' . in the vicinity cirri of borehole - t3' SB 7 is c sands, silts and clays: characterized by alternating layers of ❑ A silty sand unit extends from the surface (below 6" concrete) to 4 feet bgs. These sands are very fine to fine grained and vary in color from black to olive. There was a strong gasoline odor in these soils. s ❑ At 4 feet bgs the first clay unit was encountered. This clay was black in color and had a stronggasoline odor similar g to the silty sands above. The slightly most clays � transitioned to a brown or grey color with depth and extend to 12.5 feet below grade. White carbonate veins (effervescence with HCI application)were prominent at 11 feet 4 below grade with rare iron oxide staining in soil fissures. No soil recoverywas obtained between 12.5— 16 feet due to clay plugging of the sampler tip. { ❑ At 16 feet bgs clayey silty sand was encountered. This unit is�. veryfine grained, olive brown in color with white carbonate veins and nodules. A strong gasoline Odor was present in this unit. ❑ Below the fine grained sand are 16 feet of sand units of varying grain size and degrees of grading. The sands ranged from very fine to coarse grained in size, are olive, grey f or black in color, and are moist to saturated. Silts are present in the sands at 27 ---29 r feet bgs and all of the soils between 17—33 feet bgs have a strong gasoline odor. L. ❑ The sampler tip became plugged and there was no soil recovery from 33 - 36 feet bgs. However, the driller stated that the auger advancement was stiff through the interval indicative of silt/clayey soil. This was confirmed by noting the presence of clay on the bottom flight/drill bit after the augers were removed from the borehole. k Boring SB-8 a The subsurface 'in the vicinity of borehole SB-8 is characterized by alternating layers of sands, silts and clays very similar to boring SB-7: ❑ A clay unit extends from the surface (below 6" concrete) to 6 feet bgs. The clay has L fill elements- red brick fragments and road base cobbles- to a depth of two feet bgs. From the bottom concrete surface to a depth of 6 feet bgs the clays are dark grey to black in color but do not have a discernible petroleum odor. ❑ At 6 feet bgs the clay units transition to a grey-brown color that becomes totally brown at�7—9 feet bgs. } i� �