This post originally appeared on Orphan Road.

The state is scrambling to come up with the $4.4B it needs to replace the Evergreen Point Bridge (a.k.a. the 520 bridge). The RTID would have contributed $1B and a patchwork of funds including tolls would have covered the difference.

Now here come the Viaduct retrofit folks, arguing that the $2.3B that the state’s already earmarked for that project could be used for the 520, and we can retrofit the viaduct for a mere $1.3B or so.

WSDOT looked at the retrofit (.pdf) and pegged it at $2.3B, not including the cost of replacing the waterfront seawall. They wisely nixed the idea.

The idea of using viaduct money is a compelling one, though. Perhaps WSDOT will look again at the surface/transit option. Though it might cost as much as $2.1B (including the seawall), it could be partially paid for by the city. Mayor Nickels has previously suggested that the city would kick in up to $750M for a tunnel, between a local improvement district and having Seattle City Light pay for the relocation of utility lines.

Add to that the $200M you save by not rebuilding the viaduct, and bingo, you’re at $950M, just $50M shy of what Prop. 1 would have raised for the 520 bridge. Even if the city balks at coughing up the the full $750M, we’re still in the ballpark.