As Seattle's tunnel boring machine nears the end of its journey beneath downtown Seattle, we heard from one of the project's longtime supporters: former Governor Chris Gregoire.

The much-debated, often criticized project was launched under Gregoire's watch. In January 2008, she announced plans to tear down the aging Alaskan Way Viaduct. And in 2009, the then-governor reached an agreement with Seattle and King County leaders to replace the viaduct with a tunnel.

"A lot of hard work and tough decisions went into it," Gregoire recalled. "It was by no means an easy path. It was difficult in the legislature, very controversial there, with many people having many views and very strenuous about their views. But in the end, I knew one thing, which was why I was so determined. I went through the Nisqually earthquake."

Gregoire believes the tunnel had to be built so that the Alaskan Way Viaduct can be removed. Experts have said the viaduct couldn't withstand another earthquake.  

Related: Bertha: How we got here and beyond

But she admitted, getting the tunnel project up and running was a slow process. Bertha, as the tunnel boring machine is known, didn't actually start digging until July 2013. By then, Gregoire was no longer governor.

"We almost processed it to death," she said. "And I worried along the way while we were processing this thing to death, are we going to experience an earthquake and have the viaduct come down; and us have amazing regrets that we couldn't come together for the safety of people that need to travel in that area."

When the tunnel boring machine began overheating in late 2013, and during the two-year delay that followed while repairs were made, Gregoire says she was a bit panicked.

"The naysayers came out and said abandon it. I began to worry, do we have the guts and fortitude and patience to see it through? Because I never lost faith the contractors could do it, but I was concerned that those who were opposed would give up and those who had already been in favor of it would then give up as well, and we would be in a real disaster."

She remembers talking to the contractors and the people in charge of the tunnel project during that time.

"I said I'll keep the faith, you guys just get it done," she said.

So after supporting the tunnel project for all these years, and in the face of sometimes fierce opposition, Gregoire called Tuesday's expected finish of Bertha's journey an important milestone.

"I couldn't be more excited for the City of Seattle and the people and tourists that are going to come visit, knowing that this is going to open up that waterfront and it's going to be magnificent," she said.  "We've had major slowdowns unfortunately along the way, but at the end of the day, I am ecstatic, and I'm very happy for the people of Seattle."

Gregoire said she'll be even more excited when the Alaskan Way Viaduct comes down.

Bertha currently has only about 25 feet left to dig before the tunnel boring machine breaks through into daylight and its final destination. The final leg of the journey is expected to begin Tuesday at 8 a.m.