January 2023 berkel & Company feature

27

FEATURE STORY

T

he developers of City Ridge - Roadside Development and North America Sekisui House (NASH) have created an urban village at the former Fannie Mae headquarters complex on Wisconsin Ave NW in Washington, D.C. The use of the site, which had been vacant since early 2018, continues a trend of turning to vacant, existing structures to meet these urban areas growing needs since available space has become scarcer. Eight new structures were constructed for this development, centered around the abandoned Fannie Mae building that was left on the site. These structures include a below-grade parking structure under most of the site footprint along with 687 residential units, a 150-room hotel, about 150,000 sq ft (13,935 sq m) of retail space, and about 62,000 sq ft (5,760 sq m) of ice space. The Fannie Mae building was designed and constructed in the Colonial Revival style to mimic the Governors Palace in Williamsburg, Virginia. The central portion of the original structure was built in 1956 on pile caps with small-diameter cast-in- place piles. Two wings were added in 1962 and were supported on belled caissons. All told there were three above-grade and one below-grade level. The current development team requested its inclusion as a local historical landmark for preservation and inclusion in the new development. A large, commercial grocery store anchors the new development, and the ground level around the existing structure was lowered by approximately 8 feet (2.4 m) to accommodate this facility. Excavation depths for the below- grade parking under the remainder of the site were as much as 40 feet (12.2 m) immediately adjacent to the existing structure and up to 62 feet (18.9 m) at the rearmost portion of the site. The foundation and earth retention requirements for the project included underpinning the existing building, excavation support for the remainder of the site, and additional deep foundations to support new structures installed around the periphery of the

Award Winning Microp e Support

OF HISTORIC BUILDING IN WASHINGTON D.C.

BY RICHARD GUENTHER, PE, BERKEL & COMPANY CONTRACTORS, AND MORGAN NESMITH, PE, DGE