Complementary Construction
Story by Gene Storm

With structural steel revealing the full form of the nearby convention center in downtown Anchorage, concrete footings and a foundation are rising this summer from nearby ground where a $37-million, 10-story parking garage and retail center is taking shape. The Atwood Building Parking Center will function primarily as an 840-space parking structure for the state of Alaska's principal office building in Anchorage, with public parking that will be available to support convention center activities in the evening and on weekends.

Like the convention center location, the 32,564-square-foot site for this structure was a street level parking lot before construction began. The Feb. 1 start for the parking center project during one of the coldest winters in recent years provided an immediate challenge for Davis Constructors & Engineers Inc., the Anchorage-based prime contractor.

"The most challenging part of this project so far was doing the foundation during one of coldest winters on record," said Greg Krapff, the project superintendent for Davis. "Not only did we have to thaw the ground in order to dig, but we had to keep it thawed until the concrete was poured and cured. This became quite a challenge with strong winds and minus-30-degree wind chills," he added.

Davis crews accomplished the task by stripping the parking lot of asphalt and bringing in three large boilers connected to ground thaw hoses, which were covered with insulating blankets. The process took from seven to 10 days to allow for excavation for footings, with the thawing equipment then moved to repeat the operation at another area on-site.

Bringing the 368,000-square-foot concrete structure together will require an estimated 14,400 cubic yards of concrete and 1,500 tons of reinforcing bar.

"Another unique aspect of this job is the requirement of large No. 18 rebar and lots of it," said Krapff. At 2.25 inches in diameter and weighing in at approximately 13.6 pounds per foot, it doesn't take long for No. 18 rebar to add up quickly in a project like the parking center.

Davis decided to use Aluma Systems to form the structure, from beam and deck forms to shear wall gang forms.

"I went to Las Vegas to tour several post tension garages and talk to the contractors using the different systems before deciding on a form system," Krapff said. "Aluma not only has a very good forming system but they have an excellent engineering and design team. Aluma reps have visited the site to ensure that all of the form components are here and Davis personnel understand how it all goes together," he added.

A Tight Squeeze
Being close to the convention center project on a constrained building site in the busy downtown core presents other challenges for Davis. Logistics can spell the difference between a smooth operation and one that is in disarray, and Davis has worked hard to ensure success.

"Staging materials, earthwork, forming, concrete, reinforcing bar, and all associated activities needs to happen within a site only 20 to 30 feet outside of the building's actual footprint, and all at once," notes Krapff. "A massive coordination effort between Davis and our subcontractors was needed to ensure that this work was done both efficiently and, more importantly, with the safety of all workers kept as the absolute highest priority," he added.

Davis shares with Neeser Construction, the convention center contractor, a laydown yard located on a vacant site a little more than a half-mile from the two projects. In addition to material storage, the site serves as a critical assembly area for the multiple forming types used on the garage as well as an area to pre-assemble key reinforcing bar elements.

Traffic control around the site was an issue that Davis addressed in part by coordinating with Neeser. Davis has kept one lane of traffic open on the three streets adjacent to the project and adjusted traffic patterns to allow for one way traffic. When construction barricades were erected, the Anchorage Fire Department was invited to traverse the surrounding streets with its largest truck, Engine 1, to ensure passage in the event of emergency.

The Davis workforce, including subcontractors, will peak between 70 and 80 during the busy summer season with a project completion date scheduled for September 2008. When completed, the structure will house street-level retail businesses including a restaurant and a bank.

Being developed concurrently with the Dena'ina Civic and Convention Center and for the same owner, Alaska Center for Convention and Trade LLC, the two structures will provide a dynamic presence in downtown Anchorage.