DASH Bus Maintenance Facility

CarbonCast enclosure driven to meet the toughest challenges at William B. Hurd Transit Facility

CarbonCast High Performance Insulated Wall Panels were used on the new, 160,100-square-foot William B. Hurd Transit Facility in Alexandria, Va., due to their thermal efficiency and fully structurally composite action.

“We considered a steel structured building for the bus storage area,” says project architect Peter Schmidt, “but in order to provide rooftop parking, precast provided the ideal solution.”

Phase I of the project consists of a fully precast concrete structure including a one-story bus maintenance area and adjacent two-story wing. A rooftop parking deck wouldn’t have been possible without use of load-bearing CarbonCast High Performance Insulated Wall Panels. This contributed to significant time and cost savings while allowing room for 36 additional buses and future expansion.

Support for the 15’-wide double tees was accomplished using a combination pocket/corbel in the load bearing CarbonCast walls. The pockets penetrated the 4” back wythe without disturbing the insulation layer. Corbels extended from 7” to 8” depending on the design.

A minimum insulation value of R-14 was accomplished with 3” of expanded polystyrene (EPS) rigid foam with some panels containing 5” of EPS foam supplied for selected areas. Insulation is sandwiched between two precast concrete wythes meeting requirements for edge-to-edge continuous insulation (“ci”) defined by the ASHRAE 90.1 energy code. Concrete wythes are connected with C-GRID® carbon fiber grid shear trusses that have relatively low thermal conductivity for a fully structurally composite structure with little thermal transfer.

CarbonCast High Performance Insulated Wall Panels were fabricated off-site in a controlled factory environment and delivered for immediate erection. This eliminated concerns for material and equipment storage, weather delays and other setbacks, expediting construction and allowing other subcontractors ample time to complete their work.

“Precast saved us time,” says Schmidt. “We were able to run the utilities before the building was completely dried in.”

Aesthetically, CarbonCast panels were cast in a standard buff color in a medium sandblast finish. A light sandblast was used in the office area where a bold fluted vertical detail was cast at the panel edges. Second-story panels were factory stained blue and yellow to match corporate branding. Reveals in these panels create subtle shadow lines and help frame first floor windows. Panels were topped with a rectangular accent to disguise the caulk joints and better integrate the building with others dating from the mid- to late-1800s.

The City of Alexandria anticipated challenges with fitting the facility into the tight, urban brownfield. Its location contributed to LEED® Gold Certification and its heat island reduction, proximity to mass transportation, alternative transportation options, energy efficient building envelope and mechanical systems, including heat recovery, exemplary water use reduction, daylight and views.

There are 10 maintenance shops on grade with cassette-based in-ground lifts in all service and PM bays. Administrative offices and operations spaces are located over the maintenance area on the second floor immediately adjacent to the rooftop employee parking.

Its 260 parking spaces (including 100 spaces for other nearby agencies) can be accessed via a two-way ramp from Roth St. Direct access to bus parking on the lower level is provided from the operator’s room. Visitors may park on street level outside the administrative entrance. A total of 98 on-grade spaces are shared between visitors and limited access service parking.

CarbonCast High Performance Insulated Wall Panels were fabricated and installed by High Concrete Group LLC.