Weinstein Copeland Architects, another Seattle-based firm with experience in design and urban planning. The company is the largest manufacturer of cranes in the country, and is a primary supplier of hoists and cranes for the Air Force and NASA, including ground equipment used to move the space shuttle. The Erection Co., based in Redmond, responsible for the erection of all structural steel, including the retractable roof. Hoffman Construction of Washington, building the stadium's parking garage. Unlike conventional or mobile cranes, tower cranes offer several advantages, according to Brummond.
Tower cranes have faster swing speed and line speed.
Plus the heights of the towers varied so the lines overlapped without colliding. And tower cranes take up less room and don't have to be moved as do conventional cranes, so their use was less disruptive, both on site and just outside the ballpark. Probably the biggest factor is you can build inside and outside at the same time. The cranes made the work site safer. Conventional crane operators do not have the bird's eye-view that tower cranes do.