On his perpetual mission to undermine the plan to replace the viaduct with a tunnel, mayor Mike McGinn often points to failures of King County to do a big dig without running into huge cost overruns. The Brightwater sewage tunnel has been an ongoing financial disaster and the cost of the downtown transit tunnel, opened in 1990, ballooned by 56 percent before it was completed.
But King County Department of Transportation Assistant Director Ron Posthuma wants McGinn to stop using the county as an anti-tunnel whipping boy. That downtown tunnel where light rail now runs actually came in under budget, Posthuma claims.McGinn is basing his insistence that all tunnels result in massive cost overruns on an Oct. 2009 Sightline Institute report looking at past Seattle-area boring projects.
"Cost overruns are commonplace," the report concluded, noting the cases of the downtown transit tunnel and the 2009 light rail tunnel under Beacon Hill, which went 30 percent over budget. (Report author Eric de Place brushes off the I-90 tunnel, which was finished 54 percent under budget saying the geology of Mount Baker is better understood as the state had bored through it once before for the freeway.)
But Posthuma says the Sightline report mis-characterizes at least the downtown tunnel, a project he oversaw at King County DOT. The costs blew up thanks to problems getting the stations built along the route. The tunnel itself came in under budget. "It was a double-digit percentage [under]," he said today following a viaduct replacement briefing before the King County transportation committee. Posthuma couldn't remember the exact amount.
Wikimedia Commons Getting this underground isn't cheap. But county DOT says that doesn't mean it will go over budget.
"Tunneling happens every day, all over the world," he adds. "Some people say all tunnels come in high and that's not true."
Councilmember Jan Drago chimed in to point out that construction bids for the southern part of the viaduct replacement (which is on the surface) have come in under budget.