Perhaps it is time for a proposition on the City ballot barring spending of any city funds on construction or promotion of any new tunnel construction within Seattle city limits, or the solicitation of funds for such project(s) from any other person or organization for a period of thirty years.
If a tunnel floods or collapses (see Big Dig) there is no realistic escape or rapid access by emergency workers - odds are you will drown or suffocate in the dark, if you survive the immediate disaster. Tunnels are not good in an earthquake prone region, and with Seattle waiting for the "big one", a large heavily used tunnel is merely a ticking bomb.
Reduced throughput on the proposed tunnel will result in increased congestion on both I-5 and Downtown streets, and a shift of city employers to regions less difficult for workers and vendors to access (and which most often offer lower rents and facility costs).
Eliminating downtown exits in a tunnel solution further drives heavy traffic onto surface streets in the downtown via surface access both north and south of the downtown core - both heavy diesel and passenger vehicles added to a downtown mix already perilously close to gridlock for hours each day. Those much bemoaned vehicles transport the people (customers and workers), supplies (from garlic bulbs to the Pike Place Market to construction and industrial materials), and products in and out of SODO and the Downtown core...and will be off-loaded onto surface streets.
Cost is also a factor, particularly in a rapidly darkening economy as tax revenues shrink for both the city and state as personal revenues and property values dive for individuals, as jobs vanish and unemployment costs soar.
Digging up Second Ave for five or ten years is unlkely to improve the fiscal situation of Seattle or the State.
Historically, tunnels double, triple, and quadruple initial cost estimates - cost estimates that we already cannot afford and a fiscally stretched federal government is deeply unlikely to cover.
If the Big One comes, the current Viaduct will likely collapse, necessitating repair or replacement - preferably well before the Big One arrives.
The Viaduct replacement (as we are assured the current structure is flawed beyond recovery) needs to address the concerns above, and facilitate either current or greater traffic flow at the lowest possible cost while ensuring equal or greater access to Downtown, Belltown, and SODO.
The Mayor and Governors "Nickels Tantrum Concession" proposal is built of large gelatinous blocks of fail, and as such, needs to be shot down ASAP before the funding and idiocy begins.
Let the filing of propositions barring tunnels, lobbying of the legislature, and general political mayhem resisting this boondoggle begin.