Bridge Work
Thursday, August 16, 2007
About 12 percent of Lyon County’s bridges are structurally deficient or functionally obsolete, well below the national average of 27 percent, county commissioners were told Wednesday.
Lyon County Engineer Chip Woods gave a report on bridges around the county during Wednesday’s Lyon County Commission study session. Woods said he decided to deliver the information after hearing reports in various media following the Aug. 1 collapse of a bridge leading into Minneapolis, Minn.
Woods said a bridge may be classified as structurally deficient or as functionally obsolete, but it can’t be classified as both.
Lyon County has 29 bridges that are considered structurally deficient, which means the bridges have a deteriorated condition and have a reduced load carrying capacity.
“These bridges usually have a sufficiency rating of around 50 or less,” Woods said.
The 29 bridges listed as structurally deficient represent 7.3 percent of the county’s 395 total bridges. Woods said 13 of those bridges are closed and have been since he came to work for the county in 1988.
“They remain in inventory in case there is a need for them at a future date,” Woods said.
Of the remaining 16 bridges designated as structurally deficient, county workers already are planning to work on five of the bridges designated as structurally deficient. They are:
• Road 40 west of Road D
• Road 340 west of Road H2 (currently under construction)
• Road K south of Road 140
• Road 20 east of Road N
• Road 160 east of Road Y
Another five can be replaced by county-built bridges. The remaining six bridges are either too long for Lyon County to build or on routes that qualify for federal aid for projects.
In addition, Lyon County has 20 bridges that are classified as functionally obsolete.
“Functionally obsolete means that there is an issue of clearance adequacy, deck geometry or alignment,” Woods said. “The bridge is just not up to current design standards.”
One of the bridges in this category — located on Road M north of Highway 56 — is in the planning stage to be built by Lyon County. Local workers can work on another 10. The remaining nine bridges are either too long or qualify for federal aid for projects. These include a 48-feet stone arch bridge on Road 330 west of Admire, the Baker Bridge on Road B south of Road 270 and the Rocky Ford Bridge on Road P north of Road 140. The Baker Bridge is on the historic register, Woods said.
Woods said that, in general, Lyon County is in good shape.
“Overall, our bridges are in very good shape compared to the nationwide average,” Woods said. “A large number of these we can do ourselves. But there are a few of those that are beyond our capability.”