The problems for Seattle’s “Bertha” tunnel boring project are continuing according to the Seattle Times.

Tunnel-machine Bertha’s two-year breakdown will further delay the Highway 99 tunnel’s grand opening until 2019 and saddle Washington state with an estimated $223 million in cost overruns, lawmakers were told Thursday…

A 2019 opening would mark a full decade since former Gov. Chris Gregoire chose the deep-bore tunnel option and lawmakers approved the tunnel bill sponsored by then-Sen. Ed Murray, now Seattle mayor. Gregoire dismissed critics such as then-Mayor Mike McGinn, who warned that a clause in the bill put Seattle taxpayers at particular risk for paying for overruns…

The extra costs almost certainly would be paid by the state’s drivers in gas taxes, more transportation-fund debt, or by tolls and fees.

Tunneling is a key technology for the future of urban infrastructure. But the experience in Seattle illustrates the risk that the technology entails. It is one thing for state and federal governments to undertake this risk under the oversight of elected officials, and another for state and federal governments to put pressure on local governments and utilities to undertake these types of massive projects, as is common in the water quality and flooding arena. A tunneling project that goes well can indeed often reduce pollutant discharges or flooding at an attractive unit cost, but the costs can mount quickly when a project does not go well. Luckily, that happens only when we do not know in advance precisely what we are going to find underground every step of the way under a city that has been around for a couple hundred years (in other words, always). Tunneling is an alternative that should almost always be looked at. Green infrastructure should be looked at too and considered seriously on its merits as an engineering infrastructure technology that can have multiple benefits for the citizens, taxpayers and ratepayers of urban areas.