When the Colorado Department of Transportation (CDOT) announced it was going to replace the Fourth Street bridge in Pueblo, the news could have spelled major traffic woes for motorists with long closures and detours. The bridge connects I-25 and downtown with the city’s western residential neighborhoods and carries state Highway 96A (SH 96A) traffic across a small city street, a major complex of railroad lines, a flood wall and the Arkansas River.
But CDOT took several steps to ensure that impact to traffic will be kept to a minimum during the four-year project, Karen Rowe, CDOT resident engineer, said.
One way CDOT is minimizing disruptions is by building the new bridge to the north of the old bridge so that traffic need not be completely halted during construction, she said.
Some of the project work is being done “offline, meaning we have minimal impacts to traffic because the new bridge is just north of the old bridge,” Rowe said.
“We’re building the new bridge while the old one is running,” she said. “Actually, the new bridge is two separate bridges [one for each direction]. Once we get the north one finished without putting in the sidewalls, we will direct all four lanes of traffic onto that north bridge while we finish constructing the south bridge.”
CDOT also is restricting Flatiron Constructors, the general contractor, to 163 days for 24-hour one-lane closures in both directions. Beyond the 163 days, the company faces charges of $10,000 a day, Rowe said.
The restriction doesn’t impact other shorter closures although they must be done during non-rush hour times, she said.
“For five weeks we have traffic down to one lane in each direction to construct a new roadway in one quadrant. We’ll do that four times throughout the project. We’ll do one-lane closures in between rush hours during the day but generally we don’t need 24-hour lane closures in place,” she added.
When completed, the new bridge will be the longest span highway bridge in the state, Rowe said. “That’s from pier to pier. It’s not the longest but it will have the longest span of any bridge in the state.”
Vehicular traffic isn’t the only traffic CDOT has to be concerned with in this project. The new bridge crosses a historic rail yard.
“It’s 28 railroad lines,” Rowe said. “It’s challenging construction. There’s 23 Union Pacific rail lines that we’re crossing with a very long span of 380 feet.”
The Pueblo rail yard is a major railroad system component with tracks at the bridge location for one BSNF and two UPRR mainlines so the contractor also has to worry about keeping delays to a minimum for the rail traffic going on under the bridge construction. To do that, a tower crane is being used to move materials.
“They have flagman down there that stops the trains when needed,” Rowe said. “They’re using the tower crane to access materials from the existing bridge and then bring them into the rail yard so they don’t have to keep crossing back and forth on the tracks.”
The new bridge is necessary because the old bridge, constructed in 1958, is “structurally deficient,” Rowe said. It has a “Sufficiency Rating” of 24 out of 100.
Improvements to the bridge and roadway cross-section will be able to accommodate future traffic demands on the 4th St. Corridor. The new cross-section includes two 12-ft. (3.7 m) travel lanes, a 6-ft. (1.8 m) inside shoulder, a 10-ft. (3 m) outside shoulder and a 10-ft. wide multi-use sidewalk in each direction.
As crews are constructing the new roadway in the southeast quadrant of the project, traffic is being reduced to one lane in each direction on the east side of the bridge. That closure is expected to end Aug.16.
Crews recently reopened the River Trail bicycle route, which was closed for false work and construction of a tunnel for pedestrians under the bridge construction area.
The Northside sidewalk will remain closed for the duration of the project.
The project team includes:
• FIGG — project management and bridge engineering
• PBS&J — civil, roadway, traffic, utilities, environmental
• Ayres Associates — hydraulics & drainage
• Goodson/MWWA geotechnical, geology
• Szynskie Group — lighting and electrical design
• EDAW — urban design and landscape architecture
• Abel Engineering — survey and ROW support
Flatiron Constructors won the contract with a low bid of $27,657,855. The total cost for CDOT to build the bridge will be $35,528,190.
“Everything is going well so far, and we’re on schedule, so we’re excited to see this go up,” Rowe said.
The project is slated for completion in June 2011. CEG