Drilled Pile Design and Construction for a Former MGP Site in Manhattan-PPT Presentation

PPT Presentation

Pdf Summary

The presentation describes geotechnical and foundation design for a proposed Brooklyn development on a former coal gasification plant site, including work near and beneath the High Line.<br /><br />Subsurface conditions include 13–36 feet of historic fill, a 5–24-foot-thick confining layer, underlying sandy soils, and groundwater 7–10 feet below grade. Coal tar from the former manufactured gas plant contains hazardous compounds, including benzene and naphthalene. Remediation was completed in 2013–2014 under the NYSDEC Brownfield Cleanup Program, with ongoing requirements to protect the site’s environmental controls. Measures include a containment wall, coal-tar recovery wells, and an in-situ soil stabilization (ISS) monolith. Because the monolith is relatively new and susceptible to cracking, construction procedures require a stable working platform and restrict foundation installation methods.<br /><br />High structural loads and the need to limit ground penetrations favored high-capacity, rock-socketed caissons over driven piles. Installation methods were adapted to protect the containment systems, including isolation casings, embedment in the confining layer, and grout around permanent casing. Testing and monitoring addressed the vibration sensitivity of the ISS monolith and nearby High Line foundations.<br /><br />The existing High Line piles extended only about 30–36 feet below grade, while the project required a basement excavation approximately 25 feet deep. Investigation and test driving established that the structure was sensitive to construction. The High Line was therefore temporarily supported on caissons and subsequently re-supported on permanent caissons installed beneath its columns.<br /><br />Key lessons include investigating existing structure foundations when records are uncertain, testing installation methods near sensitive structures and environmental controls, and monitoring remedial systems throughout foundation construction.

Keywords

geotechnical engineering

foundation design

Brooklyn development

former coal gasification plant

High Line

Brownfield Cleanup Program

contaminated soil remediation

rock-socketed caissons

in-situ soil stabilization

containment wall