Site Stratigraphy Sample Clauses

Site Stratigraphy. The overburden at the Site generally consists of several feet of fill material overlying alluvial deposits. Locally, the alluvial deposits contain lenses of fine sand and varying proportions of coarser sand and gravel. In some areas of the Site, the alluvial deposits were not encountered, and thus fill material overlies the bedrock in these areas. In general, the alluvial deposits become more continuous in the upland or central portion of the Site. The alluvial deposits are considered to be alluvial flood plain deposits of the Mohawk River and were subsequently buried beneath fill. The fill is composed of various materials including sand, gravel, cinders, coal, and demolition debris (e.g., brick and concrete). Finer-grained material (silt and clay), where present in the fill, is typically not the predominant component. The bedrock in the vicinity of the Site is composed of highly deformed ▇▇▇▇ to black shale and minor siltstone with pervasive, closely-spaced cleavage planes oriented at a high angle from horizontal and is part of a lithotectonic unit referred to as the Cohoes Mélange. As a result of the orientation of the cleavage planes and slight variations in the rock competency, the bedrock surface is expected to have troughs and ridges aligned approximately north to south; this is evident in bedrock exposures in the adjacent riverbed when the river level is low. The thickness of overburden at the Site varies between approximately 6 and 15 feet; the typical thickness across most of the Site is approximately 12 to 15 feet. The cylindrical subsurface foundations of the two former gas holders at the Site contain fill from ground surface to their base; the thickness of the fill within the eastern and western gas holders is 14 and 32 feet, respectively. The cross-sections in the RI Report (Figures 6 through 11) provide generalized depiction of the stratigraphy underlying the Site.