Seattle, Washington

Working to construct a bridge in an environmentally sensitive area can be very difficult. The new 2 mile section of State Route 520 is being constructed across the Lake Washington adjacent to the existing highway that acts as the west connection for the largest floating bridge in the world. This section is 90% over water and consists of 99 drilled shafts varying from 8-12 feet in diameter with depth of up to 175 feet.

A containment area was built at each shaft location using multiple layers of a fiber reinforced plastic along with a spoils bin for direct spin off and spoils control. Constant monitoring, inspection, and maintenance were needed to ensure the operations remained contained. Spoils are hauled away in sealed trucks with concrete moving in shortly thereafter.

Polymer drilling slurry was utilized in addition to permanent steel shaft casings in the upper length of the shaft that needed to be piped using high density polyethylene (HDPE) piping and was wrapped with secondary containment in high traffic areas. A group of plumbed slurry tanks followed the operations down the trestle allowing for storage, batching and remixing.

The Malcolm team will complete all shafts by the end of 2016 with traffic running over the new bridge in summer of 2017.

For more information, please contact Adam Running at arunning@malcolmdrilling.com