Even a simple bridge replacement project, such as the one on U.S. 24 near Lake George, CO, about 40 miles west of Colorado Springs, can be interesting — especially if you reduce the time allotted for construction, throw in a couple seldom-offered monetary incentives and use a portable signal instead of flaggers to control traffic.
The 62-year-old, two-stand steel bridge on U.S. 24 was replaced with a single-span concrete girder bridge about 36 meters (118 feet) long. The bridge crosses the South Platte River. A new bridge was deemed necessary when the old bridge was rated functionally obsolete because of inadequate shoulder width. The aging structure was nearing structural obsolescence as well.
As the bridge was being replaced, 90 meters (3,000 ft.) in needed road improvements were identified and added to the project. Roadwork will improve two intersections east and west of the bridge. Left turn lanes are being constructed at both intersections and a continuous acceleration/deceleration lane is being added to run between the intersections on eastbound U.S. 24. The western intersection is the turnoff to Eleven Mile Reservoir, a popular recreation destination.
For the Lake George job, the contractor, Edward Kraemer & Sons out of Castle Rock, CO, used its own 90-metric-ton (100 ton) Link-Belt truck crane and moved most of the dirt with self-loading Caterpillar and John Deere scrapers rented from Wagner Equipment, Colorado Springs, CO. The job required 16,000 cubic meters (20,800 cu. yds.) of embankment material and 6,400 metric tons (5,760 tons) of asphalt.
Because of funding problems earlier in the year, CDOT was unable to advertise the project until June and the contractor was unable to start until mid-July, according to Jim Brady, resident engineer with the Colorado Department of Transportation. This left three months before fall began.
As most Colorado residents know, temperatures tend to dip below 50 degrees in the fall, especially at high mountain elevations such as Lake George, so completing the project before winter sets in was a concern. As an incentive, CDOT offered the contractor a $20,000-bonus if the job could be completed by Oct. 15 and $10,000 if completed by Dec. 1.
Offering early completion incentives is fairly new for CDOT, according to Brady, and the Lake George job is only the fourth one in CDOT’s Region II to have such an incentive tied into the contract. Other incentive awards, usually upwards of $400,000, have been for substantial roadwork on Interstate 25 where traffic volume is extremely heavy. “Normally, this one wouldn’t warrant an incentive, it averages about 700 cars a day. But we had that specialty circumstance of getting started late and not wanting a detour through the winter. Lake George gets a lot of snow and it would be difficult to maintain,” said Brady.
Though the job was designed in three phases, Jim Rumler, regional manager for Edward Kraemer & Sons in Colorado and project manager for the Lake George job, requested that it be changed to two phases. Combining two phases essentially shaved off a month on the time it will take to complete the job, but it also meant maintaining two-way traffic on one lane.
Said CDOT’s Brady, “After we tried it for a week, we were happy with the safety and traffic movement, so we allowed them to do it.”
Rather than controlling traffic with flaggers, a portable signal was used. “We were nervous at first and used it just during the day when we were there to monitor it at all times,” said Brady. No problems were encountered so the portable signal was used around the clock. Should it fail, Brady said, it would automatically notify those in charge.
Brady said the signal is not appropriate for all construction projects. In this case the detour was short and should it malfunction, drivers could see from one end to the other and determine for themselves when it’s safe to pass through the area.
Another interesting twist is that the project was adjacent to wetlands. Because of heavy runoff earlier last year, much of the wetlands were still under water. The contractor took precautions by surrounding the area with a silt fence to ensure sediment runoff wouldn’t enter the sensitive area. Hay bales were also used to help prevent erosion. During demolition of the old bridge, the contractor used a test bucket in which concrete chunks and dust would drop, rather than fall into the river.
Edward Kraemer & Sons, founded in 1911, is headquartered in Wisconsin with regional offices in Minnesota, Missouri, West Virginia, Arizona and Colorado.
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