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HomeMy WebLinkAboutTrans 2007-08-13 Item 3A - Discussion - Bridge Inspection UpdateTo: Mayor Mullet From: Director Public Works Date: August 9, 2007 Subject: Bridge Inspection Update ISSUE: In light of the recent bridge collapse in Minneapolis does Tukwila have any Steel Deck Truss Bridges or bridges that have been rated as being "Structurally Deficient DISCUSSION INFORMATIONAL MEMORANDUM With the recent collapse of the I -35 W Bridge in Minnesota, much of the nationwide discussion has focused on bridges being classified as "structurally deficient." Because of the media attention, unfortunately these discussions have led to confusion as to the term's actual meaning A structurally deficient bridge is one whose condition or design has impacted its ability to adequately carry its intended traffic loads. In other words, it means that a bridge has a problem and needs repair, replacement of a certain component, or in the worse case replacement of the bridge itself. If the condition is such that it no longer is capable to carry its intended traffic loads, then the bridge may be weight restricted. Being structurally deficient does not imply that the bridge is in danger of collapse or unsafe to the traveling public. The bridge sufficiency rating is the basis for establishing eligibility and priority for replacement or rehabilitation with federal funds. The sufficiency rating is a numeric value that indicates a bridge's relative ability to serve its intended purpose. The value ranges from 100 to 0. In general, the lower the sufficiency rating, the higher the priority for rehabilitation or replacement. To qualify for replacement, a bridge must have a sufficiency rating of less than 50.0 and be structurally deficient or functionally obsolete. To be eligible for rehabilitation, a bridge must have a sufficiency rating of 80.0 or less and be structurally deficient or functionally obsolete. In addition the bridges must be greater than ten years old. Tukwila has twenty (20) different bridges. Tukwila does not have any steel deck truss bridges similar to the collapsed bridge in Minneapolis. In accordance with Federal and State guidelines, these 20 bridges are meticulously inspected every two years and the 1 ti primary bridge components bridge decks, superstructures, and substructures are rated during these inspections. Tukwila does have a structurally deficient bridge Boeing Access Rd Bridge (over the railroads). It was built in 1945 and is a concrete and steel girder type bridge. Because the substructure has problems several pedestals are leaning, there is concrete spalling, exposed rusty anchor bolts and reinforcements, and some cracking and it has seismic deficiencies, it has been rated as structurally deficient. The bridge is monitored through regular inspections. The bridge's Sufficiency Rating is 22.2 and it has been included in the 2007 CIP, page 32, for replacement. Because of a lack of federal funds (funds go to WSDOT) there has not been a call for new replacement projects since 2004. The application will be resubmitted later this year. Tukwila also has four (4) "functionally obsolete" bridges S. 180 Street Bridge (over Green River), S. Grady Way Bridge (over railroads), Boeing Access Rd Bridge (over Airport Way), and 42 Avenue South Bridge. A functionally obsolete bridge is one where the deck geometry, load carrying capacity, clearance, or approach roadway alignment has reduced its ability to adequately meet the traffic needs below accepted design standards. Tukwila also has a number of bridges that are seismically deficient. Sargent Engineers performed a detailed inspection in 2003. Of the 20, Sargent Engineers has identified 10 bridges and the placed them in priority order for repairs. At the top of the list are four bridges the Boeing Access Rd Bridge over Airport Way, Boeing Access Rd Bridge over the railroads, South Grady Way Bridge (over the railroads), and the S. 180 Street Bridge over the Green River. RECOMMENDATION Continue with the City's aggressive inspection program, continue to fund repairs as part of the budget, and resubmit the replacement application for the Boeing Access Rd. Bridge (over the railroads).