Everett - DBM Contractors Inc. of Federal Way, Wash., recently completed the temporary excavation support system at the Snohomish County Justice Center here. Spanning one full city block and extending 90 ft. in depth, it is one of the deepest soil nailed excavations in the United States.

Temporary shotcrete facing and temporary soil nails were selected for the $2.1 million earth retention system. The soil nail system consisted of more than 2,100 soil nail bars up to 62 ft. long and more than 60,000 sq. ft. of mildly reinforced shotcrete facing 3.5 in. to 4 in. thick. Three-ft.dia. drilled piers were substituted for the pilasters to provide foundation support in difficult ground conditions.

Other team members who worked on this project were general contractor/construction manager Mortenson, excavation contractor City Transfer Inc., shotcrete subcontractor Air Placed Concrete Specialists Inc., and design engineer/project geotechnical engineer Shannon & Wilson.