Seattle— DBM Contractors Inc. recently completed excavation support for future construction of the Colby Garage at Providence Medical Center in Everett, Wash.

The $2.7-million project required excavations at the site ranging from 30 feet to 45 feet and DBM installing permanent top-down soil nail wall and drilled shafts. The 35,385 square feet of permanent 14-inch top-down structural shotcrete shoring walls included 1,149 soil nails and more than 197 tons of reinforcing steel. In addition, DBM also installed nearly 6,000 square feet of temporary 4-inch reinforced shotcrete facing.

The permanent top-down soil nail wall system consists of drilling and grouting rows of soil nails behind the excavation face as it is excavated and then covering the face with reinforced shotcrete. The top-down method allows construction of the permanent basement wall as the excavation extends deeper to the bottom level, shortening construction time and reducing costs of the below grade construction. In addition, DBM installed 12 each 4-foot-diameter by 87-foot-deep drilled shaft foundations on existing grade behind a soil nail wall.

DBM worked with the general contractor, Mortenson, and completed the job on time.