Square 537 - Washington, DC
City: Washington
State: DC
Owner: Trammel Crow Company
General Contractor: Helix Constructors, LLC
Project Description:
Schnabel Foundation Company was the preferred bidder for the $4.64M project which provided more than 68,000 sf support of excavation with heights of up to 68 ft below four heavily traveled CSX railway lines. The design also supported a cut of 25 ft below 16 floors of the adjacent Marriott Residence Inn and included a water pressure surchage which extended 28 ft above subgrade. Specialized equipment was necessary to install a watertight system, which included deep soil mix technology, jet grouting and a secant wall in difficult soils containing running sands, nested cobbles, and boulders over a very hard clay.
In addition to Schnabel's cutoff wall technology, the earth retention system included soil nailing, bracket piles, corner diagonal braces, and 539 tiebacks with 270 sealed penetrations through the watertight wall below the water table. Over 475 tons of steel was used to fabricate 176 soldier piles which included internal connections for tiebacks. Despite setbacks, due to difficult soil conditions and buried man-made obstructions, this project was completed in eight months (mid-August 2007 to mid-April 2008).
