SR 520 working group votes ten to two to adopt A+ option for new bridge
By a vote of 10-2, the workgroup (comprised of lawmakers representing neighborhoods on both sides of Lake Washington) has selected the "A+ hybrid" as the recommendation going forward for the highway's west end.
The two dissenting votes were Speaker Frank Chopp and Representative Jamie Pedersen, who both represent the 43rd LD. All the other workgroup members present and voting were in support of the A+ hybrid option, which incoporates several elements of earlier proposals that are no longer under consideration.
Not included in the A+ hybrid option is an expensive, risky tunnel under the Montlake Cut, which is proposed in Options K and M.
It would not be bored, as were the Beacon Hill Tunnels, or the new tunnel under First Avenue that is proposed to replaced the Alaskan Way Viaduct.
Instead, according to WSDOT's documentation, it would be built using either a combination of the cut and cover method and immersed tunnel method, or the sequential excavation method. Choosing the former would mean digging a trench under the Cut and lowering watertight tube sections underwater, then connecting the sections together. Choosing the latter would mean dividing the space to be tunneled into segments and mining each segment seperately.
Either way, including a tunnel in the design would be ridiculously expensive and cause the cost of the project to be much, much higher.
More specifically, the cost of Option M is estimated to be $3.35 billion; the cost of Option K is estimated to be between $4.07 to $4.1 billion. Compare that to the A+ hybrid, which estimates put at between $1.9 billion and $2.1 billion.
(Keep in mind, none of these figures are the total cost of the Evergreen Point Floating Bridge replacement. All of these options are for the west end only).
The A+ hybrid option calls for the construction of a second drawbridge across the Montlake Cut, right next to the existing span. The second drawbridge would force several homes to be demolished, but WSDOT's datasheet comparing the different options says that roughly the same number of parcels would have to be acquired to build a tunnel. It is true that a tunnel would result in less noise pollution (because some of the traffic would be underground) but the cost tradeoff is huge, and ill-advised considering how short of money the project already is.