JOHNSON COUNTY– Cars should travel a little slower across Mehaffey Bridge now, and big trucks will have to detour around it until a new bridge is complete.
The Johnson County Secondary Roads department placed a weight embargo on the bridge and reduced the speed effective March 11, due to too much movement as cars were driving over the bridge that is currently under construction.
“It was determined during one of the four cross beam concrete pours that the steel beams on the existing bridge, while traffic was driving over the bridge, was flexing to the point where they could touch the support forms for the new bridge beams,” said County Engineer Greg Parker. “Our structural engineer determined that speed and weight had to be reduced to minimize flexing.”
Therefore, the gross weight limit of eight tons and new speed limit of 25 mph will remain in effect until the new bridge is open to traffic. Temporary signs are posted to remind travelers to slow down, or in the case of heavy trucks, turn around. Permanent signs will be coming soon, Parker said.
The Iowa Code allows county supervisors to impose weight restrictions on secondary roads, typically for a period of 90 days. Chip seal and oil seal roads are most susceptible to damage, and late February through early May is the most common time for embargoes to be in effect.
“Typically when the roads are coming out of a hard frost, they are susceptible to severe soft spots,” Parker said. “We monitor our roadways to minimize damage by reducing the loads. This can be invoked for a maximum 90 days per calendar year to allow the road to heal itself.”
The county engineer is allowed to issue special permits for individuals who demonstrate a need to move market farm, farm feeds or fuel for home heating purposes, and whose vehicles might exceed the weight limits on embargoed roadways. Operators of overweight vehicles on restricted roads without a permit risk prosecution. Options include using alternative routes, or breaking loads into smaller units.
The existing Mehaffey Bridge over the Iowa River between Solon and North Liberty is nearly 50 years old. In 2012, the bridge– while still safe– was declared structurally deficient, and was recommended for replacement. The replacement bridge is being built around the existing span in phases, to minimize inconvenience to the public and allow traffic to flow as consistently as possible for the duration of the project. Emergency closures of short duration may be necessary as the project progresses.
Parker said the most recent construction timeline received from the contractor indicated that the project will be completed in November.
“As you know, this has been a difficult winter, with unusually cold temperatures which has slowed down the contractor from completing some tasks,” Parker explained.
A public meeting will be scheduled sometime in early May to discuss updates on the Mehaffey Bridge replacement, as well as the Mehaffey Bridge Road paving project that will take place this summer. This will be a joint project public meeting with the City of North Liberty, Parker said, but no date has been set.