In a matter of hours, A.M. Cohron & Son of Atlantic, Iowa, removed an aging railroad bridge for the Iowa Interstate Railroad and installed a new one, with hours to spare before the next train came barreling across the structure.
"On the day of the outage, we removed the existing bridge and set in place the new bridge and ensured it's functional," says Jesse Harlan, A.M. Cohron & Son Vice President and Iowa, Arkansas and Railroad Project Manager. "It was a team effort."
The Iowa Interstate Railroad, founded in 1984 after assuming control of rail lines from the former Rock Island Railroad, restored through service from Council Bluffs to Chicago. The rail line provides access to rivers and connects freight with Class 1 carriers.
The original West Des Moines steel, high-stress bridge was built in the 1940s, and in need of replacement. Iowa Interstate had little information about its construction or weight.
Bridge Swap Professionals
A.M. Cohron specializes in bridge work. This was the company's 20th single-day railroad bridge swap during the past five years. Even though that expertise comes in handy, Harlan said bridge swaps represent a small percentage of the company's work.
"They have all been quick hitters," Harlan says. "You have to get in, do your prep work in advance and in one day remove and replace and get it operational again."
The company started more than 75 years ago, after A.M. (Arch) Cohron arrived in Des Moines from Kentucky to work as a carpenter. He began as a contractor in 1928 and completed his first bridge project two years later. In 1958, the company incorporated as A.M. Cohron & Son, after Donald P. Cohron took the rains after his father's death in 1951.
Current Chairman Keith Harlan joined the firm in 1957 as a laborer. During the 1960s and 1970s as the interstate program was in full force, the company grew strong. Although Iowa based, the company has completed bridge work in other states, including Nebraska, Kansas, Oklahoma, Arkansas and Missouri.
Leaders at A.M. Cohron believe in updating and maintaining its fleet of equipment, knowing the right tools are needed to successfully build projects. That fleet includes nearly 40 crawler lattice boom cranes, ranging from 23- to 100-ton capability; dozers; loaders; excavators; hammers; and other assorted pieces.
Many of those pieces have been purchased from Star Equipment, founded in 1968 by Max and Beverly Bowman in Des Moines. The company specializes in light to general construction equipment. Today more than 70 people work for Star, which continues as a Bowman family-owned and operated business. The company offers on-site and in-house service at its four Iowa branches: Des Moines, Cedar Rapids, Ames and Waterloo.
"Whether it's dealing with parts or equipment, Jesse, Rick [Harlan, President], and the whole A.M Cohron crew are always great to work with," states Wade Snyder, Star Equipment Territory Manager.
Harlan recalls buying equipment, including excavators, track and skid loaders, air compressors, generators and water pumps, from Star Equipment for the past 30 years.
"We do quite a bit of business with Star," Harlan says. "The company is good to do business with. They treat us well."
Planning and Execution
The bridge swap started with extensive planning. In this case, A.M. Cohron spent two months preparing for the activity.
"We had a 12-hour window to remove the old and have the new back in place for the trains to run back on it," Harlan explains.
Work began by building an access road to the site, one large enough to bring in two oversize cranes. That entailed hauling in 22 semi-loads of dirt into the site. The company rented a 160-ton Kobelco crane and a 275-ton Terex crane for the lifts from RTL Equipment in Grimes, Iowa.
"It took a lot of planning to make sure we had heavy enough slings to pick the bridge and cables large enough to handle it," Harlan recalls.
A.M. Cohron trucked in the steel girders and other materials for the new 114-foot-long bridge and assembled it about 500 feet from the existing structure. Bridge assembly lasted about three weeks. The new bridge weighted 270,000 pounds.
"The most difficult challenge we had with that was trying to figure out how to lift the old bridge in one piece, without dismantling it," Harlan says. "We had a hard time figuring out how to lift it and the weight."
Yet, Harlan and his team determined the weight to be 220,000 pounds, and planned accordingly. Work started on lift day at 6:30 a.m. Both cranes lifted at once. The pick went smoothly. By 8:30 a.m., the old bridge was removed and set off to the side. Once the old bridge was down, A.M. Cohron crews descended onto the bridge foundation to drill anchor bolt holes in the existing concrete, and install concrete riser blocks and bearing devices for the new bridge. The prep work lasted until 3 p.m. "The drilling of the holes took quite some time," Harlan recalls.
With prep work complete, the two cranes picked up the new bridge, walked it the 500 feet to the foundation and set it in place. The new bridge was on the foundation by 5 p.m.
"It was the largest two-crane pick our company has done, with some pretty large cranes," Harlan reports. "They were some of the heavier picks we have ever had to make. That made this one more special."
On the day of the lifts, A.M. Cohron worked closely with teams from the Iowa Interstate Railroad, who removed the rails and ties from the old bridge and installed the new rails and ties on the new bridge. A second contractor assisted the railroad. By 9 p.m., the railroad's responsibilities were complete and ready for the next train to come through.
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