Don’t get cross over the bridge
NORTH LIBERTY– Johnson County Engineer Greg Parker has made a promise.
“Once we’re done, you’ll love it.”
Parker issued the vow Monday, April 15, at a public meeting held at South Slope Communications in North Liberty regarding the replacement of the aging Mehaffey Bridge. A packed crowd sat through a brief presentation, then directed over 20 questions at Parker, assistant engineer Ed Bartels and representatives of VJ Engineering and Iowa Bridge and Culvert about the nearly $9 million project.
The current bridge over the Iowa River between Solon and North Liberty is nearly 50 years old, completed in 1966 at a cost of $1.2 million. Parker noted in 2013 dollars, the cost would work out to $9.1 million, or a bit over the cost for the replacement span. The existing bridge, while still safe to use, was declared structurally deficient, necessitating a load limit. It’s been recommended for replacement, but federal dollars have not been available, forcing the county to look elsewhere for money to do the job.
Two funding sources were identified: one consists of money set aside when the bridge was built, which has been accruing interest ever since. The other is a bond issued by the county to make up the difference between the set-aside dollars and the actual cost.
For their money, the taxpayers of Johnson County are getting a one-of-a-kind bridge, which will be built in a unique manner.
Rather than demolishing the current bridge, then building the new one, plans call for the replacement bridge to be built around the existing span in an attempt to minimize inconvenience to the public and allowing traffic to flow for the duration of the project. Parker and the others cautioned, however, there may be periods where complete closure will be necessary. As much advance notice as possible will be given, short of an emergency closure, they assured the audience.
Work has begun and will take two full construction seasons. The project is to be completed, weather permitting, in the fall of 2014.
The work is divided into six stages, with the first stage– construction of the new piers– already in progress. Over the next several weeks, two barges will be brought in and constructed. From these barges, 150-ton cranes will put in four cofferdams, one for each pier. Water will be pumped out, material excavated, piles driven and the footings and pier stems poured to an elevation above the water.
In Stage 2, the remainder of the piers will be constructed, along with support arms and floor beams alongside and under the current bridge. The bridge will be open to full traffic at this time, and the work will be quite visible, with some up to four stories above the bridge. There also will be preparation work for the pedestrian-bike trail on the downstream side of the bridge, which will be used in later construction stages as the roadway surface.
Stage 3 will see the pedestrian-bike trail completed along with the paved trail connecting the Sugar Bottom Camp Grounds to the Mehaffey Bridge Boat Ramp. Stage 3A occurs once the trail is completed, and a stoplight system will be installed at both ends along with temporary barriers in preparation for one-way traffic over the bridge.
In Stage 4, traffic alternates one way at a time, using the new pedestrian-bike trail while the contractor removes the old bridge and finishes the new bridge’s traffic lanes. Ninety calendar days have been allocated for this with a significant monetary disincentive if the work takes longer, coupled with an incentive for early completion. The final phase, Stage 4A puts normal two-way traffic onto the finished lanes and the contractor wrapping up punch list items.
Parker said it was a major design constraint to keep the bridge open to traffic throughout the arduous process, which led to building the trail to the same capacity as the traffic lanes, and the emphasis on completing it first. The design itself is very unique, not fitting any specific bridge type. Bartels called it an innovative design and pointed to its various advantages, such as its potential for low maintenance and opening the Iowa River channel wider for better navigation. The design also will help during flood conditions, allowing water to pass more easily, while the bridge itself will be less susceptible to damage from flooding.
A variety of questions came from the audience relating to the project itself and its impact. One asked about the effect of the construction on boat traffic and was assured there would be a 200-foot wide channel open at all times. The construction barges will have flashing lights, and buoys will mark a no-wake zone, necessary for the safety of the workers on the barges. Improvement of Mehaffey Bridge Road will be done in 2014, along with the bridge construction. However, the road’s curvy east end is not likely to be straightened due in part to a large amount of bedrock limiting such an undertaking. Parker said he was looking at ways to perhaps soften the curves a bit, but the overall alignment would probably remain the same.
For those planning to access the Mehaffey Bridge Boat Ramp, extreme caution and patience will be needed during the summer of 2014, with the one-way traffic on the bridge and typically heavy traffic.
“Certainly, there will be inconveniences,” Parker said. “There’s no way around it.
“This is not your only chance to ask questions,” Parker told the crowd as he emphasized the importance of keeping the traveling public informed throughout the project. He outlined multiple ways the Johnson County Secondary roads Department will use to get the word out regarding lane closures and, if necessary, complete closure of the existing bridge. For Twitter users, updates can be obtained in real time @JCSecondaryRoad on Twitter. There is a 24-hour hotline with recorded messages available at 319-688-8145 as well as a project website at www.johnson-county.com/dept_sec_roads_bridge.aspx?id=12723. Also on the website is a link to sign up for e-mail alerts. Dynamic message signs will be used as needed to give up to a two-week notice of changes impacting travel. Two such signs were used over the past several weeks in Solon and North Liberty advising of the public meeting. In addition, press releases will be sent to local media, including this newspaper.