by Ralph Nichols 
The scheduled June 30 closure of the aging South Park Bridge means big changes are looming for motorists â€“ and Metro bus riders â€“ who regularly cross over it.
Among those most affected will be commuters, including riders on Metro routes 60, 131 and 134, who travel between Burien or Des Moines and the Boeing facilities in Georgetown or downtown Seattle.
Jack Lattemann, from the Metro Transit Division of the King County Department of Transportation, updated the Burien City Council on May 24 about Metroâ€™s plans for rerouting bus schedules to accommodate traffic disruptions caused by the permanent bridge closure.
Lattemann, a senior transportation planner, said the South Park Bridge is â€œat the end of its useful life,â€ and must be closed by King County, which owns and operates the draw span, â€œto protect public safety.â€
The bridge will close to all traffic, including bicycles and pedestrians, on Wednesday, June 30, at 7 p.m.
Traffic will be rerouted on SR-509 and Highway 99 over the 1st Ave. S. Bridge, and on Tukwila International Blvd./E. Marginal Way S.
He said the county transportation department will monitor the impact of additional traffic on SR-509 and the 1st Ave. S. Bridge. The primary concern, however, is not higher traffic volumes but the impact the bridge closure could have on emergency response times.
King County lacks funding at this time to pay for an estimated $130 million replacement for the bridge, including demolition of the current structure, which carries about 20,000 vehicles a day on 14th Ave. S./16th Ave. S. across the Duwamish Waterway.
Even if the money were available now, Lattemann said building a new span would take about three and a half years. A study determined it is impractical to build a temporary bridge until funding becomes available.
Built in 1931, the South Park Bridge is an important freight corridor for manufacturing and industrial centers in Seattle, and a regional connector to Sea-Tac International Airport, Boeing Field and the Port of Seattle.
It also provides a convenient commuter route for many residents of Burien, Des Moines, Boulevard Park and White Center.
Compounding structural problems, which imperil public safety, are unreliable mechanical and electrical systems that open and close the bridge, Lattemann told the council.
The faulty systems frequently cause delays in draw span operations, resulting in delays for both vehicles on the street and marine traffic â€“ and should be bridge not be able to operate south of the bridge.
A current update by county transportation department notes that concrete in the bridge support structure, which has withstood three major earthquakes, â€œis undergoing a self-destructive process that cannot be reversed or repaired. The heavily cracked piers are not stable and shift on their foundations.â€
Lattemann said in selecting alternative routes for the affected bus service, Metro Transit considered maintaining neighborhood coverage, minimizing travel time for riders, and minimizing increases in operating costs.
Here are some route info maps as created by King County’s DOT â€“ click on images to view larger versions:
For more information, click here  to download a summary doc (as a PDF file), which includes maps and other details.