By Jean Godden

So much has happened lately that it's hard to settle on one single topic to discuss. But, for Seattle and its future, I believe the most significant story -- surpassing an ugly, perhaps politically-motivated lawsuit filed against the mayor -- is Bertha's Big Breakthrough on April 4.

The five-story tunnel boring machine, nicknamed Bertha for the city's only woman mayor, began its journey from Pioneer Square to South Lake Union in July 30, 2013. Days before the launch, I donned a yellow hard hat and went eyeball to eyeball with Bertha, a behemoth idling in its Pioneer Square launch pit.

I snapped pictures and thought I would next see the world's biggest tunnel-boring machine sometime in 2015 when the 57-foot machine was due to emerge from a 1.7 mile Odyssey.

I was wrong, very wrong. So were many others.

During its four-year passage, Bertha was destined to encounter obstacles: equipment failures, overheating, cutter head burnout, work stoppages and soil and groundwater problems, just to name major impediments. Early in Bertha's journey there was a two-year hiatus while workers dug a 120-foot-deep recovery pit to access and lift the machine's cutter head to the surface for repair and partial replacement.

Once the new cutter head was installed in December, 2015, Bertha finally resumed tunneling. Workers stopped the machine again in January, 2016, when a barge hauling excavated soil damaged Elliott Bay piers and a sinkhole opened near the project site. There were additional delays for maintenance and inspection.

Meanwhile, Bertha's revised timeline continued to slip. As of today, managers figure the long-awaited tunnel will open early in 2019. The revised timeline -- a 29-month delay -- is only one unfortunate outcome; there also are cost overruns estimated at more than $223 million. Needless to say, lawsuits to affix blame between the state and its contractors will follow, engaging attorneys by droves.

Although Bertha's journey is completed, the two-story tunnel remains some distance from competition. Ahead are another 1 1/2 to two years to finish highway decks, lights, ventilation and signals, followed by testing and work to attach tunnel ramps to connecting ramps at north and south portals.

All that said, the Alaskan Way Replacement project has reached its most important milestone. Speaking at the breakthrough, Mayor Ed Murray called it "a transformative moment."

It's daunting to look back now at where the city has been on the Viaduct Replacement Project. Following the March 1, 2001 Nisqually Earthquake there were half a dozen ideas about what to do with the badly damaged structure.

Early on, Director Grace Crunican of Seattle's Department of Transportation had favored digging a trench-like, cut-and-cover tunnel. That solution, however, would have shut down the waterfront for up to five years.

Some critics, like former Mayor Mike McGinn, simply wanted to tear the Viaduct down and rely on surface routes to transport 100,000 people each day. Other would-be visionaries argued the Viaduct could be retrofitted, a costly fix that would have produced a structure still teetering on supports sunk in watery soil and vulnerable to the next quake.

Washington House Speaker Frank Chopp imagined retrofitting the Viaduct as a glass-enclosed roadway with an upper level park, a version derisively dubbed the "Chopp-a-duct." Civic activist Kate Martin crusaded to save the Viaduct and turn it into Seattle's version of New York's Highline. But voters said no, apparently seeing the folly of an expensive, yet unfunded idea.

Among fanciful pre-earthquake proposals was one from a utopian planner who thought the elevated roadway would make an ideal venue for luxury condos. Herb Robinson, the Seattle Times editorial-page editor, imagined attaching a wide platform to the Viaduct's West side with pedestrian walkways, a shopping arcade, plantings and scenic viewpoints.

Uncertainty about the Viaduct is mostly in the past. A well-vetted replacement project is now headed toward some critical junctures. Once Bertha's tunnel is ready to take on traffic and questions about tolls are resolved, the deteriorating Viaduct will be demolished and a wide surface road constructed. Work will begin on a nine-acre waterfront park partly paid for by assessing nearby stakeholders.

It will be well into the 2020s before that park becomes reality. But once dignitaries gather and ribbons are cut, Seattle will finally be reunited with the magnificent Elliott Bay harbor, grandest entry into any city in the world. Credit for that union belongs in large part to Bertha and her breakthrough.