The South Park Bridge, which spans over troubled water, is in trouble itself.

While the Duwamish River needs to be cleaned, the bridge above may need to go. The 78-year-old bridge cannot yet be retired, and must continue to carry 18,000 cars and 2,600 trucks per day.

With epoxy-repaired columns, shaky wooden piers buried in shallow water, enormous gears with teeth that have shifted out of line, and fuses reminiscent of those in Dr. Frankenstein's laboratory, it's an engineering marvel that the bridge still stands.

"We were dually impressed that the bridge is still operating," said King County Council member Dow Constantine at a community meeting immediately following a half hour tour of the bridge, also named the 14th-16th Avenue Bridge.

"This was an eye opening tour," Constantine said.

Also eye opening is the price tag for a new bridge, an estimated $145 million.

The tour was lead by Tim Lane, bridge and structural design unit engineer with King County.

"Rainwater leaks through cement on the bridge's surface," Lane said. "It rusts the rebar which then expands and pops out cement." He said the bridge is also seismically vulnerable and that the 2001 earthquake alone caused $750,000 damage.

As he spoke from a ledge under the bridge he was hard to hear as trucks roared overhead, as did car after car. From above, those on the bridge tour witnessed a seemingly endless motorcade of over 20 police motorcycles, and marked and unmarked squad cars. No one famous was spotted but some speculated that with that big a fuss by law enforcement it might be a dry run for a visit from presidential candidates John McCain or Barak Obama. From freight-hauling truckers to four-wheeled commuters headed to Boeing to presidential candidates, a lot is riding on that bridge.

After bridges are routinely inspected they are assigned a federal "sufficiency rating" based on structural integrity and the traffic load they are expected to carry. When the West Seattle Herald reported on a similar tour by Lane in 2005, the bridge's sufficiency rating was an eight out of a top score of 100. Today it rates a four. The Minneapolis Bridge that collapsed last August had a rating of 50 before the incident occurred.

The control tower operator opens the South Park Bridge about three to five times a day, more on weekends. Lane demonstrated the antiquated control bars that looked less sophisticated than a pinball machine from an old-time arcade.

"This is really old technology," he said. "Drum controllers. You can't buy new parts. There are different speeds to control the bridge, and instead of using the highest speed setting we salvage parts from that (mechanism) in case we need to repair the mechanics for the lower speed settings. It's all original, 1930 G.E.-made."

At the community center meeting that followed, concerned citizens spoke out.

"I use the bridge every day as a South Park resident," said architect Geoff Belau, who is concerned the existing bridge will be demolished without a replacement, an option being considered. "Things here have gone through kind of a dark period, but are settling down a little bit. Crime is down, and there are signs every day that it's becoming a real neighborhood. Without the bridge, what's been started in the commercial district...will be that much harder to continue, not to mention traffic woes on the other nearby bridges. We are already underserved with public transportation."

"'Lets build it' is easy to say and hard to do," said Bob McNeil, who moved from Fremont to South Park 10 years ago. His son, Tim, was a carpenter and popular South Park activist and respected advocate for a new bridge plan for years. Sadly, Tim died last year. His wife, Debbie, is still involved.

"I can throw a rock to the bridge from where I live," said Tim's father. "I look out my living room window and see one big truck after the other.

"A lot of people in the north know nothing about the South Park Bridge, and it takes a lot more voices saying how important this bridge is. A huge segment of population is intimately affected by the bridge and benefits from it. My concern is that the city lacks the level of concern and enthusiasm needed."

"A huge fraction of residents are interested in South Park and want to see it better," said Dagmar Cronn, president South Park neighborhood Association. "We have all kinds of groups, the South Park arts group, the Action Agenda group, organizations for traffic and trees, and the Duwamish River Cleanup Coalition. We don't have very much apathy in South Park."

Steve Shay may be reached at steves@robinsonnews.com