One of the arguments you commonly hear for a 3rd Bridge across the Willamette in Salem is the fact that we only have two auto bridges, the Marion and Center Street bridges, while many cities our size and even smaller have many more bridges. A certain right-wing radio talk show host in Salem, in arguing for the 3rd Bridge, likes to compare our town to his former place of residence, Des Moines, Iowa, which has at least seven bridges across the river that cuts through the center of that town as you can see in this Google Earth image:
What’s wrong with Salem that we’ve only built two bridges in the 160 years that we have been a city? Are we cheap? Are we stupid? What is the problem?
Simple. The problem is our peculiar topography.
As with many cities, Salem’s founders had the wisdom to find just the right place to locate our city relative to its topography. At our location, the Willamette River has two huge floodplains, both to the north and to the south. They are nearly a mile wide, and they used to flood with great regularity before the Detroit Dam was constructed in 1953. They still flood during unusual weather events like many will remember in 1996 and in 2012. We have more recently learned that these floodplains are earthquake liquefaction zones that will probably liquefy in the next Cascadia subduction zone earthquake with bad outcomes for anything built on them.
Salem was located between the two floodplains, and the Marion and Center Street bridges were built on a more stable basalt bank where it made sense to build bridges. The Willamette is in a relatively narrow channel at this location, and there is no large floodplain to cross.
If Salem had the same topography as Des Moines, we no doubt would have built more bridges over the years. But we don’t. And we didn’t.
The argument for not building a bridge to cross a huge floodplain today is the same as it’s ever been. It simply costs too much. The bridge needs to be long. It needs to be elevated. Now we know it would have to be anchored very deep in the ground to avoid the liquefaction problem. It’s just a bad idea. The official cost estimate for the 3rd Bridge is $430 – 450 million. With debt service over 20 or 30 years the cost rises close to a billion dollars.
We have eight lanes across the Willamette with the Marion and Center Street bridges. The 3rd Bridge “Preferred Alternative” would give us four more. Mayor Bennett seems to be pushing a plan to reduce the size to only two lanes. Trouble is, even a two lane bridge would cost hundreds of millions at the Pine Street to Hope Street location. If we really needed more lanes in the future, the Draft Environmental Impact Statement for the 3rd Bridge includes Alternative 2A that would add three lanes to the bridges we have, at a cost that would be considerably lower than even a two lane 3rd Bridge.
There are many reasons why the 3rd Bridge is a bad idea, but maybe the most compelling is this one: Salem’s topography is what it is, and it dictates that we use what we have already built, and make it bigger if we need to. Trying to bridge a huge floodplain is wasteful and foolish.