The New York City Transit Authority is planning a new subway line on the east side of Manhattan extending along Second Avenue from as far north as 125th Street to as far south as the downtown financial district. This will be the first new subway line in New York City in over 70 years. Subsurface conditions along the proposed alignment feature various man-made fill and glacial soils over bedrock at various depths.
YU & Associates, Inc. (YU) participated in the extensive subsurface investigation program providing boring and field test inspection services and evaluation of geological and geotechnical data. Soil boring, rock coring, in-site testing, packer testing for determining hydraulic conductivity was performed. QA analysis of rock core, and down hole geophysical testing was conducted during subsurface investigation to determine dip, direction and artifacts for interpreting geological structures and grouping of joint sets and structure families, used in producing the Geotechnical Interpretative Report (GIR) and Geotechnical Baseline Report (GBR) contract documents.
Extensive existing building foundation searches were performed to collect and compile information for geotechnical impact studies. The finite element program PLAXIS was used to model excavations for the various stations and particularly used to evaluate the slurry wall and secant wall construction.