Bad news from Beantown.

The outside engineer who investigated leaks at Boston's $14.6 billion "Big Dig" project said recently that he could no longer vouch for its safety. The project is a system of tunnels and bridges along the Boston waterfront. But it also has proved to be a system of cost overruns and construction flaws.

It's so bad that the Massachusetts attorney general recently opened a fraud investigation of the project's contractors; and Gov. Mitt Romney asked a state court if he could fire the chairman of the Massachusetts Turnpike Authority, which is overseeing the whole debacle.

Why should we care? Because Seattle may embark on a Big Dig of its own along the waterfront.

Mayor Greg Nickels wants to replace the Alaskan Way Viaduct with a tunnel along Elliott Bay.

I worry that Nickels' hard sell for the project is drowning out some of the warning signs. Mainly, the dollar signs.

Nickels' $4.1 billion plan already is getting the high-hat from U.S. Sen. Patty Murray, who called Nickels' request for $1 billion in federal funds "impossible."

Said Nickels: "The impossible just takes a bit longer."

While I appreciate Hizzoner's optimism, I appreciate my own cynicism a little more.

City leaders start talking about big projects, and I know to pull up a chair and sit on my checkbook, because it's going to take a while and cost a lot.

Is there no way to fix things without tearing down and rebuilding (City Hall, Central Library, Kingdome), nearly breaking our government bank and public trust in the process?

The concept of rehabbing public structures rather than tearing them down and rebuilding is called "conservative surgery." The concept belongs to a 20th-century Scottish planner and it was revived last month in these pages by UW professor emeritus Folke Nyberg, architectural designer Jeff Boone and landscape designer Patrick Nopp.

Not only could it save us money, but it also could save us some history and, for Nickels, some political capital.

I asked the mayor's spokeswoman, Marianne Bichsel, if he had peered into the hole the Big Dig had put Boston in.

She said the state and city transportation departments are "keeping apprised" of the project.

Besides, she said, our waterfront tunnel would be a "different type of structure" from the Big Dig.

(I don't know: a hole in the ground? Next to water? Cars drive through?)

"We have had pretty good experience with overseeing large-scale projects that go according to plan," she said, citing Sound Transit and the rebuilt I-90 bridge. "I think we're having good success in this part of the country."

Sound Transit was riddled with cost overruns until it straightened up and broke ground last year. That Bichsel would "pish-posh" that worries me. That Seattle has a pattern of tearing down and building back up worries me, too.

Nickels needs to watch where he digs. Or his optimism won't mean a hill of beans.

Nicole Brodeur's column appears Sunday, Tuesday and Thursday. Reach her at 206-464-2334 or nbrodeur@seattletimes.com. She'll keep looking.