CIR Revitalizes Colorado Mountain Pass
Jones Pass is a mountain in north-central Colorado that reaches an elevation of 12,454 feet at its peak. Nestled in the Arapaho National Forest, Jones Pass Road is the primary route for visitors to Jones Pass and also for traffic to and from the nearby Henderson mine. The Henderson mine, owned by Freeport-McMoRan, has produced molybdenum since 1976 and is North America’s largest producer of the mineral.
“Throughout the week, Jones Pass Road is used for mining operations and on the weekends, for recreational use,” said Reed Poleszak, project estimator for Coughlin Company, St. George, Utah, adding that many years of heavy traffic had resulted in severe age-related distress. That’s why Clear Creek County solicited bids for cold in-place recycling (CIR) and asphalt overlay in the summer of 2023.
“The condition of Jones Pass Road prior to the project would be considered severely distressed with potholing, alligator cracking as well as transverse and longitudinal cracking,” said Stoy Streepy, an engineer with the county. “The CIR process seemed like a good fit for rehabilitating this road based on the condition of the road before this project as well as the cost savings and the reduction in material import/export compared to a full reconstruction project.”
Although the county only has rough estimates from 2020 to illustrate cost savings, it estimates a $19 to $35 cost reduction per square yard of roadway surface between CIR and full depth replacement.
However, it was the first time the county would be using CIR, so it was important that they bring in the necessary expertise. The county hired Atlas, Austin, Texas, for engineering and design; Coughlin Company, a SurfaceCycle company, for the CIR; and APC Construction, a CRH company, to perform the paving.
CIR to Spec
CIR is a pavement rehabilitation method where the existing asphalt surface is milled, pulverized and mixed with a stabilizing agent before being repaved and compacted. The recent project on Jones Pass Road comprised a 4-inch CIR followed by 5 inches of new hot mix asphalt (HMA). “There’s quite a bit of traffic coming in and out of that mine, so such a robust structural section makes sense for this road,” Poleszak said.
APC Construction, the general contractor on the project, bid for the job in August 2023 and the CIR portion of the project began in October 2023. Although APC has done work for Clear Creek County in the past, this was one of its first CIR projects. The company brought in its sister company, APC Southern, to pave the project since it had experience with CIR and had also previously worked with the CIR subcontractor, Coughlin Company.
Although Coughlin’s parent company SurfaceCycle operates in the milling, CIR, soil stabilization and reclamation space, SurfaceCycle Chief Commercial Officer Roman Lopatko said “Coughlin is probably the company with the most legacy [with CIR] in our portfolio.”
Coughlin has been involved in a number of CIR projects in Colorado, mostly for the Colorado Department of Transportation, including a 43-mile section of Colorado’s State Highway 149 between Creede and Lake City previously reported by AsphaltPro Magazine. “That was one of the biggest CIR projects ever let in Colorado,” Poleszak said. Although the Jones Pass Road project was quite small—one lane in each direction 1 ¾ miles long—the company was able to bring decades of experience across scores of projects big and small to the project.
“We relied on Coughlin for their expertise with CIR, because they are very much an expert with that process,” said APC Project Manager Keary Brown. “We really enjoyed the collaboration we had with Coughlin. This was a really good team effort.”
Also key was the role Atlas played in the CIR mix design and acceptance testing for Clear Creek County. Atlas has significant experience in quality control for CIR projects, frequently working with Coughlin Company when it picks up CDOT jobs, said Atlas Quality Assurance Manager Davis Quinn. “CIR is not hugely popular in Colorado, with most agencies preferring full depth reclamation,” he said. However, Quinn said, this road presented an ideal opportunity to use the process given the significant surface degradation and cracking paired with the good condition of the underlying material.
According to Dan Shellhammer, who is responsible for SurfaceCycle’s CIR projects across the nation, the Jones Pass Road was simplified and streamlined by Colorado’s existing CIR spec. “Colorado has a great CIR specification,” he said. “Coughlin Group, along with some other folks in the industry, was instrumental in helping them get that written.”
Having a solid standard to rely on made the CIR portion of the project run smoothly. “We basically came in and performed the work to specification,” Poleszak said. “It was a very straightforward job for us.”
The CIR portion of the project began in early October and was completed within two weeks. Coughlin milled to a depth of 4 inches—a total of 24,000 square yards of material—with its Roadtec RX900e rotomill followed by its Roadtec RT500 recycling train, utilizing Suncor for the emulsion and Lhoist for the lime mineral filler.
Coughlin utilized Suncor’s CSS Special emulsion formulated for cold recycle work injected at 3.5% and Lhoist’s hi Calc Quicklime Fines to slurry for the 1.5% mineral filler additive according to Atlas’s mix design.
“We essentially just mixed it and put it in a windrow for [APC Southern] to pick up and pave,” Poleszak said. The most significant challenge during the CIR process was the weather.
“Ahead of this project, we were busy finishing up a CIR project in New Mexico and APC was busy paving Berthoud Pass,” Poleszak said. Then, a cold front moved in just as Coughlin mobilized its equipment for the Jones Pass Road job. “With CIR, you’re putting quite a bit of water into the mix and if it’s too cold that is not going to get out of that mix as quickly as what would be desirable.”
The company discussed with the county and Atlas some additive options that they’ve used in the past to help material cure more quickly under similar conditions (higher elevation, colder temperatures) in its home state of Utah. “We’ve had some success introducing cement into a mix design in other climates with cold weather,” Poleszak said, as the Portland Cement reduces the water demand for the CIR mix. “Now, it’s become our standard for these cold weather temps to help get traffic back on here with minimal raveling and distresses.”
However, the county opted to utilize its existing design given the body of testing data it had on lime and emulsion. And, ultimately, the original mix design ended up working out well.
Coughlin ended up starting a bit later in the day than it otherwise might have so it could operate during the warmest part of the day. Everyone involved ensured all testing requirements were met. “We really relied on Atlas on site to ensure all material was meeting the specifications,” Poleszak said. “Had we not met the specifications, with the cold weather and everything else, we wouldn’t have continued. But once we saw we were meeting spec, we just rolled right through it and got it done.”
“After Coughlin performed the CIR, we followed behind, paving and rolling what they left for us in a windrow,” Brown said. Then, the APC Southern crew placed a 3-inch lift and a 2-inch lift of asphalt (Grading SX with PG58-28).
The CIR portion of the project comprised 24,000 square yards of material, while the overlay required a total of 6,802 tons of HMA produced at APC’s plant in Golden, Colorado.
“The only other challenge we faced would have been the distance from our plant up to the project which was approximately 40 miles, but we overcame that with adequate trucking,” Brown said, adding that the company had more than 30 haul trucks dedicated to the project. “We used best practices to retain heat every step of the way.”
After CIR began, Coughlin hit an unexpected snag—literally. “We ran into paving fabric within the 4-inch depth of the recycle that was not in the bid documents,” Poleszak said “We were still able to meet our production rates, but we had to have a couple guys yanking fabric out of the screen deck full time. It was just one of those things that happens sometimes.”
Care Gets Results
“We are pleased with the completed project and hope to have extended the service life of the road surface by another 20 years,” Streepy said. Coughlin and APC share this sentiment.
“We were pleased enough with it to submit it for a sustainability award with the Colorado Asphalt Pavement Association,” Brown said. “We decided to submit this in the sustainability category because that was one of the reasons the county decided to do this type of pavement application up there. They wanted to try to utilize the existing materials that are there and incorporate them back into the project, as opposed to milling and hauling the millings away and then overlaying.”
“This project was a good candidate for CIR and it came out well,” Poleszak said. “If you have a good candidate for a CIR project, they sell themselves. You’re saving a lot of money and getting quite a lot of structural section back out of the road.”
Although Streepy said the tight curves and steep grades of most of the roads in Clear Creek County don’t allow for the long vehicle trains required for CIR, he said the county looks forward to the opportunity to utilize CIR in the future when the road conditions allow.
“This is an exciting first for the county,” Brown said, “and we can’t wait for them to see the results of this project and how CIR will help in the longevity of the road.”
For more information on, visit SurfaceCycle’s website.
The Rise of CIR
According to Shellhammer, SurfaceCycle has seen a growing interest in cold in-place recycling in the Colorado region in recent years.
“CIR is an alternative to conventional construction that could drastically reduce carbon emissions, so I think the state and the counties in the state are seeing that as a much more viable option,” he said. “There’s been a lot more interest in CIR as Colorado comes out with some initiatives related to tracking emissions and things like that.”
Shellhammer said he’s been seeing greenhouse gas reductions of up to 90% comparing CIR to conventional processes. “We’ve seen individual projects where they’ve reduced their CO2 output by up to 3,000 metric tons on one job.”
However, just as important to the growth of CIR has been innovations in equipment and quality control. “CIR has been around for decades, but the really great thing that’s happened in the last decade or two is the equipment industry has modernized a lot of tools that we use,” Poleszak said.
For example, grade and slope control systems available on today’s milling machines. “We are milling for depth, but we are also trying to get some of those bumps and dips out the road while we’re doing that,” Schellhammer said.
Also, the closed loop screening system on recycling trains. “That’s a machine control feature that’s been put in place to ensure 100% of that RAP is sized appropriately,” Schellhammer said. As the material goes into the pugmill, an inline weighbridge monitors the weight of the RAP. “That’s tied to an onboard computer that then meters the amount of emulsion that’s being added back as a percentage by weight. Those are all going through very accurate calibrated pumps, so we’re able to make a very consistent cold mix.”
“In the past, there was none of that,” Shellhammer said. “There wasn’t a weighbridge. There wasn’t an onboard computer. All it was was basically a dial on the side of the machine you turn up or down for adding more gallons per minute versus less.”
Before these equipment innovations, roughly one to two decades ago, Shellhammer said the industry struggled with material consistency. “With the advancements that have been made, NCAT is actually testing to see if they can increase the structural value of cold mix. Because it is more consistent now, they may not need to be as conservative in the design phase when looking at a job.”