• City Manager
• City Clerk
• City Attorney
• Finance
• Parks and Recreation
• Senior Services
• Marina
• Community Development
• Court
• Police
• Public Works / Engineering
  • Surface Water Management
  • Transportation
  • Permits
  • Maintenance
  • Current Projects

---

Search this site:

Advance Search

North Twin Bridge Improvement Project
16th Avenue South

The north twin bridge is one of two bridges the City owns and maintains along 16th Avenue South.  The north twin bridge is located just south of South 250th Street, and consists of a two-lane vehicle bridge that spans McSorley Creek.  The bridge is a three-span cast-in-place box girder design constructed in 1951 and is 212 feet long with an overall average width of 28 feet.  The center span is the longest span at approximately 80 feet.  Twin square concrete columns with portal ties support the box girders.

State and Federal law requires that agencies routinely inspect all bridges in their system.  Information from these inspections is input into the State’s bridge information system.  As part of the most recent bridge inspection, a load rating analysis was conducted for this bridge.  The results of that analysis indicated that a weight limit should be posted for the bridge.  On August 1st, 2006, a 20 Ton weight restriction was posted for the bridge.

This bridge is in need of several improvements which include seismic retrofitting, pedestrian improvements, and guardrail.  Prior to this area being annexed into the City, King County made similar improvements to the south twin bridge, which is located several hundred feet south of the north twin bridge.

As the City began design of the improvements in 2008, it was discovered that about 25% of the spread footing supporting the bridge was undermined and a large cavity existed under the west column.  The bridge was closed on March 27th, 2008.  The City working quickly to make immediate shoring repairs in order to prevent structural damage to the bridge and to get the roadway reopened for traffic.  The bridge was eventually reopened, but one of the conditions for reopening the bridge was the posting of a 10 ton weight restriction until the permanent repairs could be made.

The City is nearing completion of the design for improvements to the North Twin Bridge.  Given the nature of the needed repairs, the City received a bridge rehabilitation grant in 2008 that will cover the majority of the costs associated with these repairs.  Repairs are expected to cost approximately $2.5 million, of which about 20% of the project costs will come from local revenue sources.

Construction of the improvements is anticipated to begin in June, and continue through November, 2010 - exact dates are not known at this time.

Unfortunately, in order to facilitate the construction of the necessary bridge repairs and improvements, a partial Road Closure will be required through much of the major construction.  During construction of the improvements, the bridge will be limited to northbound traffic only.  Southbound traffic will be detoured to either Pacific Highway South or Marine View Drive.  In addition, it is anticipated that the Contractor will need a complete Road Closure to all traffic, which is likely to begin sometime in late June or early July.  The duration of the full closure is anticipated to last up to 6 weeks.
If you have any questions about this project, please contact Dan Brewer at (206) 870-6581.