While on a visit to the future Roosevelt station site recently, STB tipper Leslie B. heard that one of Sound Transit’s tunnel boring machines (Brenda) hadn’t moved in a few weeks. We reached out to Sound Transit, and Kimberly Reason told STB that the problem was a large boulder:
Brenda (TBM #1) has stopped mining since July 22nd , and has been undergoing inspection and repairs. Mining is currently expected to resume next week, following a final inspection and readiness check. Evidently, Brenda encountered a boulder large and hard enough to damage several of the teeth on the TBM cutterhead. The inspection and repairs have been carried out to date without incident and per plan. Brenda is currently 1500 ft. from U District Station. No delay to the overall scheduled is expected.
Brenda is now a veteran, having been refurbished from the ULink project prior to working on the Northgate Extension. Though this stoppage was unplanned, teeth wear is very common occurrence, and the anomaly here seems to be the rate of wear caused by the boulder. So this bears no similarities to the more systematic bearing and sealant problems of another famous TBM you just might be familiar with.