Caltrans Resurfaces 48-Mile Stretch of Interstate 8
A Smoother, Safer Ride: Caltrans Utilizes CRCP to Resurface Multiple Segments of I-8 in Imperial County
While the news has been filled with talk of the border between the United States and Mexico, there’s also a massive roadway project going on in the area. The project involves resurfacing a 48-mile stretch of Interstate 8. The road begins in San Diego, just off the shores of the Pacific Ocean, and continues into Arizona. The section being worked on is located in the Southeast corner of California in Imperial County. The construction involves some innovative techniques.
The project was broken into five segments. This was done because, “We didn’t want the whole stretch under construction at one time,” says Ismael Salazar who has served as the Project Manager for all five segments. “Breaking up the project into smaller segments also made it more manageable construction and design wise.” In addition, the smaller segments encouraged more contractors to bid, which resulted in a lower construction cost.
Funded by the State Highway Operation and Protection Program, the original estimated cost of the project was just under $340 million. Salazar notes all five segments will come in under budget. The overall price will be lower than expected for a couple of reasons.
“The design team did a good job, which meant few change orders,” says Daniel Hernandez, who is serving as the Resident Engineer for segments four and five. Michael Oreiro, the Project Engineer for segments four and five says, “We learned lessons from the earlier segments that we were able to apply to the later segments and move quicker. There was an increase in the budget for this project for the risk factor if things went wrong and fortunately nothing did.”
Construction with CRCP
The segments of the project also differed in their state of disrepair. The first three segments, which are already completed, were in worse shape than the final two. On those first three segments, the entire roadway was removed and replaced. The replacement was constructed via Continuously Reinforced Concrete Pavement (CRCP).
Constructing with CRCP is fairly new to the California Department of Transportation (Caltrans) and had not been used on a project of this size previously. Steel reinforced bars are placed within the concrete along the entire length of the pavement. CRCP naturally forms tight transverse cracks to evenly transfer loads. “The rebar within helps keeps cracks from forming, which means water will not get in and do damage,” says Oreiro.
CRCP also results in a continuous, smooth-riding surface capable of withstanding the heaviest traffic loads. The life span for CRCP pavement may be up to 70 years while the roads are typically designed to last 40 years. Because there are no transfer joints on the roadway, the road will be smoother with less bumping action for vehicles. The results are good for both the vehicles and the road itself.
This section of I-8 being worked on sees significant traffic. In addition to local traffic, the freeway is used by cross border traffic, farming equipment, and trucks transporting product between Mexico, California, and Arizona. “The farming equipment that travels in this area often moves at slower speeds and therefore travels on the shoulder,” says Donaldo Martinez, Transportation Engineer for all five segments. Because of this, the shoulders are undergoing the same CRCP construction as the travel lanes of the freeway.
While CRCP has greater upfront costs, there are benefits that make it worth the costs. Since there is no cracking, less maintenance will be required, which means greater safety for drivers and Caltrans highway workers.
A Brand New Process
The final two segments of the project are undergoing a process that has not been done in California. The CRCP is being overlaid on the existing roadway. While the first three segments of the project took just over a year, construction on the final two segments began in mid-2017 and is expected to be complete at the end of 2019. “Removing the existing roadway and replacing it with CRCP can be done quicker than overlaying,” says Martinez. “Some of the pavement beneath the final two segments was bad, and it had to be fixed before construction could take place.”
In those segments where the CRCP is being overlaid on top of the existing roadway, the freeway profile will be raised about a foot. However, there will be a smooth and seamless transition between segments. Overlaying means the concrete does not have to be as thick, which is another cost savings.
The project included recycling wherever possible. The materials used for the final two segments were made from the recycled concrete from the first three segments. The contractor was required to process and stockpile the material to be used in these last two segments. In addition, the rubberized hot mix asphalt used on the ramps throughout the project was made with recycled tires. There was also an environmental concern involving the use of water, particularly since California has been experiencing drought-like conditions. In order to mitigate for this, a dust palliative was used for dust control rather than water.
Weather and Traffic Concerns
Weather conditions in the area are intense as temperatures can reach up to 120 degrees in the summer. “While the temperatures were not a constraint as defined in the specifications, they were a concern as they speed up the time the concrete sets,” says Hernandez. In order to maintain the construction schedule, 3,300 cubic yards of concrete needed to be done per day. This mass production requires great attention and means everything is moving faster. In order to alleviate the added pressure of heat, construction crews laid concrete from midnight to 8 a.m.
Traffic handling through the construction area is also an issue. The goal was to keep as many lanes open as possible at all times in both directions on the four-lane freeway. The specifications did not allow for a full freeway closure. The contract also stipulated not to close consecutive ramps. Construction was done on one side of the interstate at a time. The side in use was divided with one lane in each direction. While this meant a slow-down in traffic, it still flowed without backing up. Hernandez credits the speed reduction signs and warning signs for enabling this.
For two of the segments, the state partnered with the county so traffic could be detoured to a rarely used county road that is just 100 feet off the interstate. A small detour ramp was constructed to get to the frontage road. “It was a win-win situation as the county got an improved smoother road,” says Salazar. “And the contractor for the state was able to work faster.”
Bikes are allowed to use this stretch of the interstate. When the interstate was reduced to one lane in each direction, there was no room for bicyclists. “As per the contract, we had to find a method to get bikes from one area to another,” says Salazar. “We provided a shuttle to pick up bicyclists and drop them off at a safe place down the road.” A phone number was made available via a robust outreach program so bicyclists could call the service.
In segment five, a knockdown machine (modified paver) was used to provide constant load and thickness of the concrete in front of the paver that increases smoothness. Two lanes and the two shoulders were paved at the same time, which meant the paving machine had to be especially wide at 39 feet. Again, this increased smoothness.
With the repaving of Interstate 8 in Imperial County, California nearly complete, commuters can look forward to a smoother safer ride. Due to the innovative techniques that were employed, Caltrans won’t need to do anything on the road for a long time.