Florida, Mo., may spark recognition in the minds of many Americans as the birthplace of writer Samuel Clemens, a.k.a. Mark Twain. The author of Adventures of Huckberry Finn was honored in namesake by many local attractions, including Mark Twain Lake in 1984, owned and operated by the Army Corps of Engineers.
Mark Twain Lake is Northern Missouri’s largest lake with more than 18,000 acres of water and 285 miles of shoreline. The construction of the Clarence Cannon Dam on the Salt River in Ralls County formed the lake, which is situated about 120 mi. (200 km) northwest of St. Louis.
All seven bridges that cross Mark Twain Lake are scheduled for routine repairs, and bidding for the first contract was let in May 2011.
PCI Roads, LLC of St. Michael, Minnesota was awarded the first contract for $2.7 million. The contract includes work on three bridges — the North Fork and South Fork of the Salt River (Route 107), and Route FF. PCI began work in February 2012.
“The bridges were all constructed in the mid 1970s in preparation of the creation of Mark Twain Lake, and while they are still in relatively good condition they are in need of preventive maintenance work to extend their life,” noted Christopher Knapp, P.E. Transportation Project Manager for the Missouri Department of Transportation (MoDOT). The preventive maintenance of these bridges was identified as a regional priority, and funding was allocated accordingly.
Work on all of the bridges includes minor substructure repairs, making concrete girders integral at stepped bent caps, and small amounts of half-sole bridge deck repairs. Crews are replacing pin and hanger connections with a shelf system; rocker bearings with laminated neoprene pads; and old expansion joints with new ones. Finally, they will remove and replace the waterproof membrane and asphalt wearing surface.
Subcontractor Bleigh Construction Company is performing all of the hinge modifications. This work consists of replacing the existing pin and hanger systems with the shelf systems and PTFE bearings.
Chester Bross Construction Company was subcontracted for the surfacing work on the bridges. Bross will remove the existing wearing surface, install a seal coat and the SP125 asphalt wearing surface.
Both Bleigh and Bross Construction Companies are located in Hannibal, Mo., where Mark Twain spent his childhood.
The coring work is being carried out by Concrete Coring Company of St. Louis. Concrete Coring is coring-out the existing anchor bolts and creating wells for the new anchor bolts. They are also performing the coring for the dowels required to make some of the bearings fixed rather than expansion.
Crews are working twelve-hour days, seven days a week to finish the bridges in the time allotted. The bridges are being closed for up to 30 days each, which has affected local residents by forcing them to use detours that are significantly longer. Fortunately, off-season traffic is fairly light in the area.
What MoDOT and PCI didn’t anticipate was the slew of ill-fitting bridge parts that they encountered while trying to rehabilitate the structures.
“The major issue that we have been dealing with is that the existing bridges were not constructed exactly as the plans [stated],” explained MoDOT Resident Engineer Jeff Gander, P.E.
“Coring out of the existing anchor bolts was difficult since they were not originally placed correctly. This required us to cut through the anchor bolts themselves when coring, rather than just cutting the surrounding concrete.
After installing the bearings and attempting to lower the girders to their final position, it was discovered that the upper and lower halves of the bearings were not fitting flush. In some cases minor adjustments could be made to make the bearings sit flush. Other cases required bearing stiffeners to be trimmed to allow the bottom flanges to flex, thereby allowing the bearings to fit properly. These problems stem from the existing girders not being true.
When attempting to bolt the new finger plate joints into place, things did not “fit right,” for lack of a better term. The expansion joints were fabricated with virtually no adjustment so in order to get the proper gap, the contractor had to get creative. They fabricated shims and trimmed existing members where necessary. All of this took a lot of time and manpower which put us behind schedule.”
Gander continued to explain the biggest delay on the project.
“After the PTFE bearings were installed, it was discovered that they had been fabricated incorrectly. New bearings (upper half only) are being fabricated at this time and will be installed mid-May. This will require us to close the road a second time so that the girders can once again be jacked up and the new bearings installed. This work will require approximately a two-day closure on both of the Route 107 bridges.”
Despite all of the design and construction issues, MoDOT plans to have the three bridges open by Memorial Day for the tourist season.
The total amount of concrete for all seven bridges is relatively small, approximately 200 cu. yds. (153 cu m), since most of the concrete work is the replacement of the deck and barrier curb at the expansion joints.
Three of the bridges are between 1,000 ft. and 2,000 ft. (305 and 610 m) in length. The seven bridges have a total of 258,000 sq. ft. (23,969 sq m) of bridge deck, therefore, approximately 4,000 tons (1,814 t) of asphalt will be installed to replace the wearing surface. CEG
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