GeoDesign is providing professional geotechnical, geostructural and geoenvironmental engineering services and related construction-period support to John P. Picone (JPP) for their construction of the Site P Station Entrance for the No. 7 Flushing Line Extension (Borough of Manhattan), for the the MTA/NYCTA.
The Site P Station is located between 34th and 35th Streets and 10th and 11th Avenues. The Station design and construction includes deep soil and rock excavation to depths over 100 feet below ground surface, to connect the new Station entrance with the existing AMTRAK tunnel and 34th Street Station Cavern. GeoDesign is designing the support of excavation (SOE) systems in both soil and bedrock, including related management of environmental conditions (ex., contaminated soil and groundwater) encountered during the work.
GeoDesign developed a construction impact assessment report (CIAR) and completed design packages for the support of excavation in soil (spanning from street level to the top of bedrock). The SOE design included tied-back soildier piles and lagging systems directly adjacent to existing structures, and design of interim structures to facilitate construction sequencing and concurrent construction activities. Unique aspects of the SOE soil work included requirements for phased excavation and concurrent detensioning of existing tie-back systems supporting site access to the Amtrak tunnel. Mechanically stabilized earth (MSE) construction systems were designed for protection of existing building structure foundations.
Geoenvironmental work included stormwater sampling for NYCDEP Discharge Permits and soil sampling and environmental analyses for UST removal. Soil and groundwater contamination encountered during excavation work required environmental sampling, analysis and characterization of contaminants. GeoDesign developed soil management requirements and guidelines for both off-site disposal and beneficial on-site reuse alternatives.
A CIAR and design packages were developed by GeoDesign for temporary support of rock excavations (for Phase I and II excavations). The designs required periodic field mapping of rock structure and joint sets and related rock mechanics analyses to evaluate kinematic failure modes and required rock bolting and support systems for the conditions exposed by rock blasting. The designs included excavation sequencing requirements for the removal of rock and installation of reinforcement at the exposed rock faces adjacent to existing structures. Supplemental rock structure and support designs were also developed for crane pad construction and surcharge loads adjacent to vertical rock cuts.
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