Light rail on the 520 bridge. Nelson/Nygaard Consulting Associates

The powers that be in Olympia say it's too late to draw new lines on the state's blueprint for a replacement 520 bridge. Instead, after 14 years of planning that Seattle officials mostly ignored, state lawmakers and transportation engineers are ready to begin pouring concrete for a $4.65 billion highway from Bellevue to I-5 that would widen the floating span across Lake Washington from four lanes to six lanes but lacks any dedicated lanes for transit. It's slated to be done by 2014. This late in the game, according to state lawmakers who chair transportation committees in the state house and state senate, there's no room for a new Seattle mayor to jam light rail into those plans.

But Mayor Mike McGinn thinks that conclusion is wrong—and he's got a report, he says, that proves it.

Consulting firm Nelson/Nygaard issued the report on April 6. It found that demand for light rail will increase in the next 20 years and that going ahead with the state's design now will likely prevent us from ever building light rail on the bridge in the future. McGinn adds that, according to this report, planning for light rail could be done for the same amount of money the state has committed to spending on the current bridge design, and that it could possibly be done faster.

But McGinn faces opponents—including state legislators, the governor, and city council members—who say this vision is a nonstarter. First, the state never studied plans for light rail; beginning that kind of study now would take 18 to 24 additional months, according to Governor Chris Gregoire. That's time we don't have, she argues, because the Washington State Department of Transportation (WSDOT) says the dilapidated bridge could sink in high winds or an earthquake, taking lives with it. Moreover, light rail costs money—money that the impoverished state, city, and county governments don't have.

The challenge for the pro-transit side is in making the counterpoints, which the study and McGinn are now outlining.

The Demand: First, the consultants found that transit ridership across the 520 corridor was about 15,000 trips daily in 2008. They estimate that "transit ridership on the corridor will reach more than 27,500 trips per day by 2030." McGinn says that proves it makes sense to build light rail—or at least plan for it.

The Logistics: McGinn is pushing the idea, among various potential alignments on the table, that two of the six lanes must exit at Montlake and be dedicated from the outset to transit (like buses) but be readily convertible to light rail once we can afford to lay the track and purchase the trains. To do this, the report finds the state would have to modify its plans in three ways: include a gap between the east and west portions of the bridge near the Arboretum to allow light rail to veer north toward the future Husky Stadium light-rail station, widen that same portion of the freeway slightly to accommodate the larger train cars, and build floating pontoons with sufficient buoyancy to hold up the heavier trains. In one of the scenarios, light rail and transit would have dedicated access on a second drawbridge across the Montlake Cut.

The Urgency: Failing to build this way essentially precludes light rail in the future. Attempting to convert the bridge and the Montlake interchange's current design in the future to hold light rail—instead of planning for it now—is "financially impractical" and "environmentally challenging," Nelson/Nygaard found. Moreover, it would likely entail expanding 520 into an eight-lane bridge, which "from a policy perspective, is unacceptable to the city of Seattle."

The Time: This plan would require the center lanes be dedicated for transit, which the state never studied, and would delay construction by up to two years. Critics of light rail say building a new bridge is a public-safety emergency. But McGinn points out polling that finds widespread support for light rail and a set of neighborhood groups contemplating a lawsuit against the present bridge plans. Going forward with the current design "may lead to litigation delay," McGinn says. "So if we can come up with a proposal that has more popular support, because it meets our vision of light rail, protecting parkland, and not bringing more cars into Seattle that gridlock local streets and I-5, we can get this done faster."

The Money: Only $2 billion of the $4.65 billion bridge's estimated cost is accounted for, the report found. "Given this shortfall and the urgency of addressing the public safety issues associated with the floating bridge," the report says, "it is highly likely that the project will be constructed in phases." Those phases should include making sure it can include light rail, McGinn says. recommended