Unlike Seattle and its Alaskan Way Viaduct replacement project, there will be no tunnel controversy in SeaTac--the Port of Seattle has opted for a bridge.
SeaTac City Council members approved April 12 an interlocal agreement with the Port for a bridge crossing over South 188th Street in the vicinity of 28th Avenue South. The aerial crossing would be part of the Port's South Access Road connecting to the state Route 509 Extension.
Of course, the SR-509 Extension has been delayed for years and no one can predict when it will be approved. SR-509 was slated to extend beyond its present dead end at South 188th Street to connect with Interstate 5. The connection was planned to expedite freight traffic between Seattle and the Kent Valley.
But, although much of the design work and right-of-way acquisition have been completed to the point where many consider the 509 project "shovel-ready," construction funding has been elusive. That leaves the freight truck-free SR-509 through Burien as a private freeway for Highline residents.
While the SR-509 Extension project has an indefinite construction start date, Sound Transit board members are expected to vote in July to expand light rail service in SeaTac to South 200th Street by 2016.
So SeaTac, the Port and Sound Transit must agree where structures will be placed in the narrow area just south of the airport, according to SeaTac senior planner Al Torrico.
"The Port of Seattle needs assurances that the city will stick with the aerial option," Torrico declared.
Port planner Tom Hooper told lawmakers the Port had considered tunnel and bridge options for crossing 188th.
But a tunnel would need north bound and south bound surface roads separated on either side of the tunnel while the aerial design would place the surface streets under the bridge making for a narrower project.
Hooper said a bridge would have less property impacts, be cheaper and have a shorter construction time.
"The aerial option makes a heck of a lot of sense," Hooper noted.
Mayor Terry Anderson said she was concerned the bridge route would go too close to airport fuel tanks located near 188th Street.
Hooper replied the route would pass well to the east of the tanks.
