Dr. Walkup followed through by conducting a study and polling the students who expressed a desire for a covered multi-purpose facility on the Northern Arizona campus. The students wanted an on-campus facility that would include a skating rink plus room for athletic events and entertainment programs. Dr. Walkup then developed a plan to build a covered multi-purpose complex for multiple uses. He began by consulting Architectural firms and asked for proposals.
The Architectural firm of Rossman & Partners of Phoenix was selected to design the facility and they presented the idea of a glued laminated timber dome that would cover 6 acres under one roof. Most of the funding for this project was provided by the Arizona State legislature and after plans were completed the University accepted the $6.6 million base bid from Mardian Construction Co. in August of 1975. Western Wood Structures acted as a sub-contractor to Mardian for design and construction of the VARAX style timber dome.
The 502’ diameter facility was very economical even by 1975 standards because of its unique style of construction. A natural bowl at the site was further excavated to allow for the domed roof to rest on 36 concrete buttresses at ground level. This “Ensphere” design eliminated the need for expensive outside support walls. As a result, athletic events as well as most of the spectator seating takes place 30 feet below ground level. There are 15,200 permanent seats but capacity can be increased to 20,000 with temporary end zone seating. The timber roof is designed to support the huge volumes of snow that accumulate in Flagstaff.