The Sound Transit Board of Directors passed today a $2.1 billion budget and schedule for extending light rail from UW to Northgate by 2021. Included in the budget are measures for improving walkability to Northgate Station and a pedestrian bridge over I-5. Passing below the radar of this news, however, is the purchase of steel rails and high-compliance fasteners for the U-Link line under Capitol Hill and Montlake. This is an important step toward mitigating sound and vibration issues discovered during tunnel mining last fall.
The fasteners are part of a $7.1 million railway hardware purchase that had to be expedited to allow for increased lead time due to high demand. Sound Transit recently conducted real-world operation studies in the Beacon Hill Tunnel and determined that high-compliance fasteners would help U-Link stay below federal guidelines for noise and vibration.
“Basically, they have a much higher rubber content than normal fasteners and are specifically designed to reduce noise and vibration from the rails,” says Sound Transit spokesman, Bruce Gray. “Our experience during mining operations played a big part in the decision. That gave us concrete data about noise and vibration interaction with the underground conditions along the alignment.”
The operations track design is very different from the temporary supply track used to haul tunnel spoils during mining and excavation of the cross-passages. “The rails will sit on a new concrete bed along the length of the tunnel and the rails themselves will be new, continuously welded rail along the entire alignment. No clackety joints,” says Gray.
A community meeting at Miller Community Center has been scheduled for July 11th from 6-8pm to discuss expected noise and vibration levels during operations.