McGinn's Consultant: Tunnel Risks Unprecedented

The state's planned 54-foot diameter highway tunnel beneath downtown Seattle would face "unprecedented" risks as it's dug through adverse soils and high water pressure, a consultant hired by Seattle Mayor Mike McGinn said Thursday.

In a preview of a report he plans to publish Friday, Thomas Neff, a Boston-based civil engineer with a doctorate in geotechnics, said it's questionable how the $1.9 billion tunnel project would turn out.

"This is a major complicated infrastructure project," he said. "The one thing that dwarfs everything else -- This will be the largest bored soft-ground tunnel in the history of the world. It is beyond precedent. So that would normally give any rational person some pause about how easy it might be to do this."

Neff spent three weeks reviewing materials that WSDOT has developed over years. Still, he said his expertise was sufficient to make an analysis. He said the challenges in terms of fighting varying soil conditions and high water pressure would be unique to this project.

McGinn spent $40,000 for Neff's services to examine how the city might be financially vulnerable if the state proceeds with the tunnel-replacement for the Alaskan Way Viaduct. The City Council is preparing to sign off on agreements with the state Transportation Department that essentially would allow the project to continue forward, but McGinn wants language inserted that would block it unless state lawmakers agree not to hold Seattle responsible for any potential cost overruns.

The state has capped its contribution at $2.4 billion, plus an additional $400 million from tolls on the tunnel when it opens in 2016. But a provision in state law says any potential overruns would be paid for by Seattle-area property owners who benefit from the project.

The tunneling portion is estimated to cost about $1.9 billion, WSDOT says about $415 million has been set aside for inflation and cost overruns, although tunnel opponents question whether that will be enough. McGinn's critics say he's trying to kill a project he never liked. They also complain he's wasting an opportunity to take advantage of cheap labor and materials during the down economy with delaying tactics.

The council hired its own consultant, who reached many of the same conclusions as Neff about the risks of drilling in the region's glacially compacted till. But the council's consultant, John Newby, said the risks could be managed and avoided to some extent with strong oversight and by learning from lessons of other tunneling projects. He also said the size of the state's boring machine would only be slightly bigger than the largest tunnel boring machine built to date.

McGinn has been an outspoken tunnel opponent. Neff is president and founder of OckhamKonsult LLP, a Boston-based consulting firm. Google his name and you'll find an article he wrote in "Tunnel Business" magazine titled "Bulls**t as Applied to Tunneling Projects." He once was vice president at Parsons Brinckerhoff, one of the lead engineering firms on the preliminary tunnel design, and was involved with monitoring deformation on Boston's notorious "Big Dig" project.