Drivers traveling on I-70 in De Beque Canyon, Colo., may notice that the highway now feels much smoother.
They might give this a passing thought of appreciation, but then forget about it completely, simply taking for granted that this small aspect—an easier means of getting to work or school or off on a visit—of their lives has improved. Little do they know how much time and attention was given to make their driving experience safe and smooth.
In letting the $7.6 million I-70 resurfacing project in April 2015, the Colorado Department of Transportation (CDOT) was of the mind that, regardless of the complicated nature of the project, the rehabbing of this particular stretch of road was a crucial investment in state infrastructure. While resurfacing projects are not, on the whole, what would ordinarily be considered “complicated,” for contractor Elam Construction Inc., the geographic situation of I-70 made that word an almost gentle euphemism.
What’s the deal?
To begin with, the stretch of road in question, between mile markers 49.44 and 60 near exit 49, was located in a sheer canyon next to the Colorado River, with steep rock walls to the south and the river itself to the north. The winding highway hugs the canyon wall, leaving little room for construction machinery and resulting also in varying surface temperatures. From the outset, construction in the tight canyon created unusually narrow working conditions and traffic-routing complications.
Compounding this difficulty, the high canyon walls blocked all cell signals, thus communication by cell phone was almost impossible in the area. Even trickier, due to the high traffic volume through the area, a large portion of the construction would have to be performed at night, a not-uncommon road project circumstance that nonetheless introduced an added safety concern, given the project’s topographic situation. Numerous curves and limited shoulders on either side of the road presented safety concerns, as did the constant presence of high-speed traffic.
A dedicated safety manager was designated by the contractor to visit the De Beque Canyon site to protect both employees and motorists. Elam devised a safety protocol plan, which was in place as soon as boots hit the ground, and all employees were dedicated to it.
Getting down to it
During nighttime construction, more than 38,000 ft of concrete median and shoulder concrete barrier wall was demolished and replaced.
Over the course of the entire project, fully 20% of the asphalt millings were reclaimed and reintroduced into the fresh HMA mix.
“Elam Construction was doing the removals of existing barrier wall and could easily have outpaced what we could place in one night, so we had to run as efficient as possible, not to let them be more than 2,500 linear ft in front of us, which was the biggest gap we were allowed between our work zones,” said Mike Adcock of Adcock Concrete. “All stringline, equipment, rebar, etc., had to be removed from the roadway after each shift. There were many pieces of equipment and people in a small area. The ready-mix trucks had a lengthy round trip because there were minimal areas for a turnaround.”
In addition to the concrete removal and roadbed reconstruction performed in preparation for the asphalt work, approximately 30,000 ft of guardrail was adjusted and repaired by Ideal Fencing.
Once the site was ready, more than 52,000 tons of hot-mix asphalt (HMA) was in line to be laid, along with 3,000+ tons of binder. The asphalt used was CDOT-specified SX100 PG 76-28. The mix contained 20% reclaimed asphalt millings from the project, which were processed and introduced into the mix. The optimum asphalt content was 5.6% using Suncor PG 76-28 with 1% lime added at the hot plant.
The asphalt plant was located approximately 25 miles from the median of the project, a challenging distance given the winding outlay of the road. Twenty-five belly dump trucks were used to transport asphalt from the plant to the paving operation, where the mix was dumped in front of a Weiler E550B windrow elevator and then deposited into the paver hopper.
The westbound lanes of the project were milled 2 in. and then paved, at 300 tph, with a single 2-in. mat using a Cat AP1055E paving machine. The mat behind the paver had to be constantly monitored for temperature to allow the compaction and finishing rollers adequate time to consolidate the mat. Both a Cat CB64 breakdown roller and CB54 intermediate roller made two vibratory passes at high amplitude and low frequency, with an occasional third pass by the CB54 as needed. The finish roller, another Cat CB54, was used to remove marks as needed.
Following the successful completion of the westbound lanes, Elam was able to alter its traffic management scheme and get in some daytime construction on the eastbound side, including milling and paving (to the same depth and specifications), construction of rumble strips, post-paving striping, placement of signage and final clean-up.
While there were an exceptional number of rain days on the project, due to the site’s relative elevation—17 days alone during the placement of the barrier—which further complicated the process, crews were able to work steadily without undue excess added to the project timeline, which had accounted for marginal delays in the planning phase. As for the resulting smoothness of the new asphalt surface, the contractor received a smoothness incentive payment from CDOT.
Adcock said, “Overall, we felt we met or exceeded the production rates we were shooting for.”
Doing it at random
Along with CDOT, consulting engineers Yeh and Associates Inc. tested the asphalt mix as it was produced at specified random intervals. CDOT voids acceptance specifications were required on this project, which called for engineers to measure air voids in the completed mix and maintained a specification band for asphalt content, voids and VMA.
Moreover, CDOT required volumetric control on this project. QA samples were taken at random at the rate of one sample per 1,000 tons and tested for air voids, VMA and asphalt content. Three verification samples were taken at the beginning of the project in order to verify the mix properties prior to paving, including gradation. In addition, one sample per 10,000 tons was taken in order to ensure continued verification of the design for all properties, including gradation. QC samples were taken by Elam at the rate of 1 per 500 tons throughout the project and tested for air voids, VMA and asphalt content. QA and QC samples were compared throughout the project in order to make sure that the results were within tolerance for multi-lab testing. A nuclear gauge was used on the project for mat and joint density testing after an initial test strip of 500 tons was core- and gauge-tested to establish a co-relation.
A challenging win
With all said and done, workers agreed that the most difficult aspect of the project, by far, was having to work at night.
“The most challenging aspect of the project, in my opinion, was the nighttime construction,” said Jim Cox, Highway Construction Division Manager for Elam. “Safety was stressed at all times due to the restricted visibility of the employees, as well as the traveling public. The confinement of the canyon restricted the room available for the men and equipment, so there was a lot of activity in a small space. I feel a lot of credit should go to the employees, supervision and traffic-control operations, as well as to our working hand-in-hand with CDOT.”
“Getting the concrete wall done at night, safely, also was a challenge,” agreed Trevor Woolley, assistant project manager for CDOT. “We did it safely without tempers flaring up too much, and we worked together. It was a great team. You had to remember everybody was here with the same goal—do a great job and complete the project on time, safely. With that said, things at 2 p.m. don’t upset most people; however, the same things happening at 2 a.m. can really piss people off. But I am happy with the results. Speaking for myself, I look forward to working with [Elam] again.”
Even with the immense challenges, CDOT, doubling down on its satisfaction with the work thus far, has opted to extend the project beyond its original limits, furthering its intent to resurface I-70 and eventually tying the project directly into U.S. 6, taking the project into July 2016 for final completion.
“Most drivers on the road only want the project done so it stops impeding their routine,” said Jim Shea of HDR Compliance, which was CDOT’s consultant on the project. “Luckily, their drives through De Beque Canyon are now unobstructed, and they should be grateful for the care and attention that went into making their drives that much smoother. It takes a lot more hard work than they would ever expect.”
As James Shea, consulting project manager for CDOT, said, “The true test of a good mix is how it survives in traffic over time.”
For that, only time will tell. R&B
