On April 8, 1988, workers complete primary excavation of a pair of 18-foot diameter tubes and five stations for the downtown Seattle transit tunnel. Work had begun on March 6, 1987, and the tunnel will open for service on September 15, 1990.
The tunnel was designed and engineered by TRA and Parsons Brinkerhoff. Construction-Pamco and Atkinson Construction/Dillingham Construction served as general contractors. Boring the primary tubes employed a pair of 140-ton mechanical moles called shield excavators.
Progress was marred by encounters with unanticipated soil conditions, one fatal construction accident (killing Alan Sandbow), and a racially charged scandal over the inadvertent use of banned South African marble that ultimately led to the resignation of Metro Director Alan Gibbs. (He was succeeded by Richard Sandaas, former Metro Transit director, who was succeeded in turn by Paul Tolliver.)
Despite these obstacles and distractions, the downtown tunnel was completed on schedule. When the tunnel opened for service on September 15, 1990, the federal Urban Mass Transit Authority hailed it as one of the most cost-effective transit project in the nation.