Geology of the Overburden Deposits and Constraints on Engineering Design for Foundation, Queens, New York City

Overburden materials, collected from depths close to the surface to plus 200 feet into the bedrock, near Maspeth site, Queens, New York City, consisted of a zone of non-compact fill materials (10 to 25 feet thick), underlain by a compressible peat layer associated with calcareous clay and shell fragments (4 to 10 feet thick). Presence of shell-bearing unit close to the surface may be indicative of a buried estuarine complex in this area. The organic clay and peat layer were underlain by loose to firm tills composed of sand with gravels often intercalated with thin silty clay lenses. This is in turn underlain by thick dark to black, red, mottled, and semi-plastic to highly plastic clay often associated with saprolites displaying relict foliations, and evidences of kaolinitization and chloritization. In places, dark to black, highly plastic clay exhibits the occurrences of disseminated pyrite and carbonaceous materials indicating anoxic and restricted paludal depositional setting. The building construction on this site poses a serious problem considering the lack of soil strength. The current upper ground horizons are not sufficiently strong enough to withstand the required loadings estimated at near 1200kips for some locations. The foundation support system will therefore be established in the till. A system of piles is anticipated to be used for foundation support. The placement of the piles may either be in clusters at each column location or through a distribution of piles over the site with rigid slabs and grade beams used to distribute the heavy loads among the pile supports. Geoengineering data of the soil samples including ASTM classification, Atterberg limits, moisture content, organic constituents, and pH of the representative soil samples will be evaluated prior to submitting a feasible design plan for foundation facility in this area.