Building a deep-bore tunnel would allow more vehicles to travel through downtown than if we simply tore down the Alaskan Way Viaduct, but it would also put 28,000 more vehicles a day on downtown streets than we have now because it would lack exits, according to the state’s supplemental draft environmental impact statement (SDEIS). The document—which is alarming some local experts on these sorts of studies—identifies many other impacts of replacing the Alaskan Way Viaduct with an underground highway. Some of them are listed below.

A couple disclaimers: This SDEIS that we’re referring to is a draft of the draft, which the state intended to shield until October but relinquished due to a records request. So things will change, but not a lot. The document is "pretty close" to the draft that will be released, says WSDOT's Ron Paananen, "but there is still editing to do." It’s really long, detailed, and technical; this write-up is not a definitive analysis of the contents (you can download them for yourself here and reach your own conclusions). That said, here is some of what's inside:

A Different Goal and No Alternative: The state shifted the goal of the project to focus on capacity for vehicles. Although the state previously examined alternatives for replacing the viaduct in 2004 and 2006—with a new elevated freeway or a cut-and-cover tunnel—those studies gauged the ability to “maintain or improve mobility, accessibility, and traffic safety for people and goods." This new study's purpose is specific to "providing capacity for automobiles," points out City Council Mike O'Brien, who was a stakeholder in the group working on viaduct alternatives in years past. "Things like increased investment in transit, better managing on-street parking, better signage, investments in bike lanes—all of these things may be the best way to move people and goods, but don’t qualify as solutions because they are not providing for auto capacity, they are managing demand.”

The SDEIS addresses this change by saying, “The project’s purposes and needs were updated to reflect current state and local priorities” from the city and federal agencies.

But redefining the purpose of the study could be a problem (and not just an explicit clash with a state law targeting reduced carbon emissions and the city's carbon-neutrality agenda). In this case, omitting alternative metrics—specifically any transit-enhanced alternative to the tunnel—actually calls into the question the legitimacy of the study, says David Bricklin, an environmental and land-use attorney who has spent 30 years examining documents like this DSEIS. “The alternative analysis is the heart of an EIS,” he says. The only remaining alternative to the tunnel is a surface/transit option, Bricklin says, because voters soundly rejected the other options in 2007. But this study—specifically being about capacity for vehicles—ignores the surface/transit option. “How can you have an assessment of the two remaining options where you only look at one of them?” he asks.

State law says that the impact study must be completed before authorities can officially decide to build any major project—the study informs their decision and compares options. This study won’t be done until next May or June. Predisposing the government’s choice to one option clashes with the point of the process, Bricklin says. “The governor, legislature, and city council seem to have their minds made up and they are just going through the motions of preparing the environmental analysis,” says Bricklin. “It is backwards and it’s a violation of the law.”

Moreover, “They did not study the recommendations from the 2008 stakeholder process,” says Cary Moon, a member of that stakeholders group and director of the People’s Waterfront Coalition. “They only study the bored tunnel and compare it to the two alternatives rejected in the 2007 vote. This seems cynical and dishonest.”

Downtown Could Handle More Cars (Maybe): If a tunnel is built, downtown could accommodate an estimated 496,600 cars passing a central point per day by 2030; if the viaduct were simply closed, only 447,500 cars a day could pass through the city core. In other words, the benefit of building a tunnel is that the city's core could accommodate 10 percent more traffic than if we just rip down the viaduct. But the tunnel itself would have less capacity than the current viaduct, which has downtown exits where lots of the traffic gets off. The study says, “most of the 30,000 daily trips on SR 99 through midtown would be accommodated elsewhere in the transportation system.” Of those, "about 28,000 vehicles per day would shift to downtown city streets." As an example of the importance of those exits, current traffic analysis shows that 110,000 cars use the viaduct at Yelser Way but that tapers down to 63,000 a day at the Battery Street Tunnel. “While the streets can handle it,” says Moon, “it is a lot more traffic added to city streets than tunnel fans were expecting.”

It doesn’t Account for Tolling: Oddly, this study doesn't plan for tolls—which are inevitable and will drastically alter traffic projections. This is dishonest. The state needs to come up with $400 million from tolling to make its budget, as dictated by a 2009 state law, and that’s what the state plans to do. Peak-hour tolls would be $4 one direction and $3.50 the other, according to estimates released this January in another document from WSDOT. That previous tolling report—which isn’t used for the traffic analysis described above—shows that more than half of the traffic would divert to downtown streets when it opens in 2015 and about 40 percent would divert by the year 2030. In lieu of that analysis, traffic projections are skewed to show that more people would use the tunnel than would really use it. But in reality, drivers would use other routes instead, further adding to downtown street traffic. Those numbers “would be low enough to call into question the very need for the facility,” says Moon. The mayor’s office noted this omission in a letter to the state, and, in reply, the state said it would add a chapter to calculate the impact of tolling in future iterations of the study.

More Greenhouse Gas Emissions: Building a tunnel that increases car capacity will result in an increase of roadway emissions from 988 metric tons per day in the downtown core to 1236 metric tons by 2030. Not a shock. This is what you expect when building a highway.

Noise Will Decrease: Right now, with the viaduct in place, sound is monitored downtown at 68 locations, and noise exceeds allowable limits at 48 of those. With the tunnel—the highway underground—that drops to only 40 locations.

Parking Will Decrease: In all, we lose 570 parking spaces (out of 6,000), most near the southern portal. “Not really a big deal,” says Moon.

Jobs Aren’t the Reason: This will create 480 jobs, which isn’t a lot for the $3.1 billion the state is spending, says Moon. “So much for the 'jobs' argument,” she says. “Our tax dollars seem to be going toward multinational engineering firms, consultants, and lawyers.”

Risk to Downtown Buildings: Digging a tunnel will create significant vibrations from the 56-foot wide tunnel-boring machine and will require hauling out an estimated 1.4 million to 1.5 million cubic yards of soil from under downtown. Removing that material and given the soil conditions—clays, silts, shifting sands and other sedimentary materials—creates a risk of ground settling under buildings. “Effects on historic resources during construction could occur from settlement,” the SDEIS says. Two buildings, the Western Building and Polson Building, “may experience severe settlement that could damage the buildings. The Western Building is in poor structural condition and settlement may cause further extensive structural damage, if unmitigated.” And even then, “Mitigation measures to protect the building may not prevent the need for demolition to avoid the possibility of collapse.” In addition, 12 other buildings—all historic buildings except the Federal Building—may “experience utility disruptions, and cracks or other aesthetic damage from settlement that could be repaired.” It continues, “Other buildings above the tunnel alignment may potentially experience non-adverse effects, such as utility disruptions, minor cracks that require interior painting or repointing of brick walls, or slightly sticking doors and windows.” It’s interesting that cracks in buildings along the two-mile alignment is called a “non-adverse effect.”

Find more in the documents for yourself here.