Tunnel Work Continues at the Access Pit
SEATTLE, WA Seattle Tunnel Partners (STP) has spent much of the week backfilling the SR 99 tunnel access pit. Crews stopped backfilling on mid-December to repair a mixing arm that broke off inside the machine during testing of the cutter head. Backfilling has since resumed and will continue.
STP indicates they may fill the remainder of the pit with a concrete-sand mixture in addition to material removed during excavation. Using the concrete-sand mixture - rather than sand and soil, as STP previously planned - could reduce the time it will take to complete backfilling. Additionally, the deep dewatering wells that have been used to control groundwater in the pit may be turned off sometime in January. STP previously planned to turn them off this month.
STP says they plan to move the SR 99 tunneling machine forward by late December, the date shown in their most recent schedule. As part of their testing program, STP intends to tunnel forward a short distance in the pit before taking a break for the holidays. After the holidays, STP plans to mine out of the access pit toward a planned maintenance stop approximately 450 feet to the north. Along the way, crews will mine forward and install tunnel rings while continuing to run tests.
The state cannot verify the contractor's schedule, but will continue to provide updates as STP's work progresses.