Our Work
The Claret
The Project
A 12-story condominium development, featuring two levels below grade, was planned for the Mount Vernon Triangle neighborhood of Washington, D.C., amidst existing structures to the south and west. The southern building, standing at 2-to-3 stories, had a shallow foundation positioned at the property line. To maximize below-grade space for the new development, excavation up to approximately 25 feet deep was required immediately adjacent to the existing southern building, necessitating underpinning. Conversely, the western building had a deep basement that did not require underpinning.
year
2023
Location
950 3rd St.
NW
Washington, DC
Scope
Underpinning
Category
Multi-Family
General Contractor
James G. Davis Construction
General Contractor
Architect: DCS Design
Structural Engineer: SK&A
Geotechnical Engineer: Geotechnical Solutions Inc.
Challenges and Results
One of the primary challenges faced during the project involved designing the building around, and working next to, a Heritage Tree. Additionally, adjacent construction to the north, combined with the presence of the Heritage Tree, left only one access point into the deep excavation. Tiebacks were restricted to the south due to conditions at the west, north, and east.
The solution for sheeting and underpinning incorporated drilled soldier beams (with a short mast to accommodate the Heritage Tree limbs), hand-dug underpinning reaching approximately 25 feet deep, tiebacks positioned at the south, lagging, and internal steel bracing.