Snoqualmie Casino Podium Tower, Snoqualmie, WA (2023)

Shoring System: Permanent Anchored Soldier Piles

Client: DBM Contractors Inc.

General Contractor: Skanska USA, Inc.

Shoring Contractor: DBM Contractors Inc.

Shoring Face Area: 31,200 Square Feet

Wall Depth Range: 27 to 85.5 feet

Status: Completed 2023

The casino expansion included a new hotel structure located north of the east end of the existing casino. The below-grade portion of the structure extended anywhere from 27-ft to 85.5-ft below existing site grades and was to be a permanent structure but without any permanent earth retention loads acting upon it. The project was particularly challenging for the following reasons: (1) soil conditions included up to 40-ft of fill underlain by medium dense to dense recessional outwash deposits and the lower soils included lacustrine silts; (2) the depths up to 85.5 feet meant that movements could be a real problem, and when combined with the permanent nature of the wall, the loads were going to be much higher than are normally dealt with in practice; (3) the existing Casino building was immediately adjacent to the south wall and on spread footings; (4) and the west end of the south wall was so close to the existing casino permanent shoring that the new anchors had to be weaved between the complex pattern of existing anchors. All of these factors resulted in a relatively heavy anchored pile wall with up to ten levels of anchors and HP14x89 piles on 5-ft centers, in order to bring the anchor loads down to a practical range. In the end, a design-build solution involving Ground Support, DBM Contractors, and the geotechnical engineer Golder Associates would utilize heavily anchored piles, pile toes with beams raised above the bottom, and a higher design load for movement reduction, that resulted in walls that moved less than 1/2 an inch on all sides, despite the relatively soft fine-grained soils.