The city council's viaduct oversight committee just got a briefing from city budget staff, who assessed the likelihood that the city will have to ask voters for more money to pay for proposed future capital projects.

The upshot: The city has as much as $604 million in unfunded capital projects that may need to be funded in the next five years, and the ability to pass just $190 million in debt over the same period. (City policy caps debt service at 7 percent of the general fund, of which 6 percent is already committed.)

Those projects include things like replacing the waterfront seawall, fixing Linden Ave. N., replacing streetlights throughout the city, and making improvements to the waterfront as part of deep-bore tunnel construction.

The council has already affirmed that it plans to go to voters, perhaps as soon as next year, to ask for new taxes to fund seawall replacement; they're considering two options that do not include Mayor Mike McGinn's proposed seawall property tax, which he wants to put on the ballot this year.

Council members also brought up several new potential property taxes, including a special parks district to pay for parks maintenance, a metropolitan arts district to help fund things like replacing the Seattle Center Fun Forest, and a library district to take pressure off the city's general fund, which pays to run the city's libraries.

Libraries, in particular, are facing major budget problems; last year, the entire library system shut down for a week because of a $45 million citywide budget shortfall.