Gensco retail, distribution facility
Designer/engineer: AHBL
Owner: CMKM LLC
ABC members: Acoustics Northwest, CHG Building Systems, Heiberg, Kirby Electric, White Cap, American Drapery Blind & Carpet
The Gensco retail and distribution facility, the third building added to the Gensco Fife campus, connects to an existing building and provides multiple access points into Gensco's facilities. The third building is 118,000 square feet with 12,000 square feet of retail, branch offices and storage space over two floors. It was built using tilt-up concrete panels.
The project's first challenge arose during the design phase when revised FEMA flood plain elevations required that a large portion of the 35,000 cubic yards of fill to be placed under the new building would need to be offset with an equal amount of compensatory on-site flood storage — about 500,000 cubic feet in volume.
With high ground-water levels preventing deep excavation and the site layout not allowing for a large storage footprint at grade, general contractor Rushforth negotiated an alternative design, using a 7-acre off-site property for flood storage. The 22,000 cubic yards of fill generated by the off-site excavation was used for fill under the new building pad.
The city council passed a first-of-its-kind easement agreement that allows the compensatory storage site to be a city park, with a walking path and wetland buffer planting systems.
Tying the existing building to the addition was another challenge for Rushforth. The existing building foundation was placed on auger-cast piles due to unresolved ground settlement issues. Although the new building's location would not likely have those issues, Gensco wanted the new building elevation to match the existing building. To do that, 6 feet to 8 feet of fill was needed, which produced substantial download on the existing foundation.
Rushforth resolved this issue by using a series of alternative structural supports including: placement of a 10-inch structural slab on 57 auger-cast piles for the new section closest to the existing building; installation of geofoam blocks in place of fill dirt; the use thickened reinforced transition slab without piles; and installation of a standard 6-inch reinforced slab on grade, which accounted for 80 percent of the floor area.
By not putting the entire building on piles, the team saved time and money.
Rushforth completed much of the work on weekends or at night to minimize disruption to Gensco's operations. It also created phased temporary parking areas to provide spaces for employees and customers during parking lot construction and new utility tie-ins.
The project finished on time and nearly 10 percent under the original budget, despite record-setting rainy weather during the roof construction phase.
Rushforth had zero reported injuries while logging in 38,887 worker hours.