Here’s a couple of things that don’t typically go well together: asphalt paving and the month of November in Missouri. There are, however, exceptions.
The rehabilitation of Hanley Road, which traverses the city of Clayton, Mo., was one of them.
For a few frazzled weeks last November, crews from St. Louis-based Pace Construction, along with partner members of the road’s owner, St. Louis County, took a broken, degrading, but crucial downtown corridor and transformed it into the smoothest ride in town and consequently added more than 10 years to its life.
This is the story of how they did it.
The stretch of Hanley Road in question runs 1.6 miles from just north of I-64/I-40 further north still to Pershing Avenue, drawing an almost clinically straight line through downtown Clayton, the county seat. The topography describing this area is typical of the American Midwestern modestly sized city: office parks, apartment complexes, residential developments, law firms, retail businesses, hotels, quick-carry and casual restaurants, and a smattering of government facilities, including the St. Louis County Courthouse. It is a high-traffic, high-volume part of town that sees a lot of in and out but very little through.
According to county estimates, Hanley Road is among Clayon’s most heavily traveled byways, averaging some 30,000-35,000 vehicles per day.
“Downtown Clayton is kind of a destination,” Jesse Jonas, engineering supervisor for St. Louis County, told Roads & Bridges. “Washington University is not far away, and there’s lots of people coming in and out for work. People who work in Clayton live all over St. Louis County, so a car is essential. There’s a MetroLink rail station and a bus system, as well; we get a lot of bus traffic during Cardinals [baseball] games. Hanley Road is a major north-south corridor in that sense, too. And, of course, lots of trucks doing deliveries to all the local businesses.”
Compounding the “pounding” the road takes due to traffic volume, Hanley also is “one of the oldest roads in the county and has some of the oldest utilities as well,” said Jonas. County engineers, following a lockstep protocol of annual road rating throughout its jurisdiction, had found that this portion of Hanley was rating a 3/10 on the PASER scale, making it ripe for rehabilitation. “In addition to the oxidized asphalt [in that location],” Jonas added, “it also had a lot of patch work done over the years due to utility repairs. It was definitely time for a fresh surface.”
Any road in need of repair is notorious for something, usually potholes or longitudinal cracking that causes upsets in the ride and keeps drivers hovering gingerly over their break pedals. Sometimes, however, it’s more significant than that.
“That stretch of Hanley was notorious for water main breaks,” David Wrone, public information manager for St. Louis County's Department of Transportation, told Roads & Bridges. “The pipe underneath, it is very old cast iron and had a long history of constant breakage. As a result of all the excavation over time to fix those breaks, the road was in a bad state of disrepair.”
At the project’s outset, before any work took place, county engineers got together with the Missouri-American Water Co. to address the break history. They learned that the lines underneath their worksite were 80- and 100-years-old, respectively. It was no big trick for them to suss out that the 100-year-old one was the primary culprit. The county thus agreed to yield the site to Missouri-American in order to get the failing main replaced—which they did in time for an April start.
“By April, we’re good to go,” Jonas said. “We worked for about two months when, wouldn’t you know it, the 80-year-old line starts to go. So, we yielded the road back to the water company and started working with our contractor on a revised schedule.”
As it had its fingers into multiple paving pies in the area, Pace Construction was willing and able to accommodate the county’s request—a decision that both benefited the county and was somewhat self-perservative, given what contractors knew of Missouri-American’s future plans.
“The water company was concerned that the water main was too fragile to withstand the paving and vibratory rollers and what that would do to their system,” Ryan Casey of Pace Construction told Roads & Bridges. “They had a project that was scheduled for a year after we were going to be finished paving, which would call for about 14 pavement cuts—right into the new pavement we would put down, so basically they sped up their schedule and we delayed ours and they got in and lined that old water main.”
The choice to line the main, rather than fully replace it as they did with the earlier failing main, was made in order to expedite the process and give the county and contractor a comfortable window in which to pave. The plan was for Missouri-American to be done and gone by Oct. 1.
The milling and paving took place at night to minimize traffic disruptions.
“We were planning on a Superpave SP125CLP 76-22 oil for the mainline mix, which makes for a stiff mix,” said Jonas. “Paving with it in cold weather was kind of a wild card, and we were concerned. But Oct. 1 was going to give us enough time. Well, there was a delay in materials and Oct. 1 became Oct. 15, and then the liner leaked on pressure testing, so that added even more days. A lot of this was out of the water company’s control, and luckily, we were already talking about using warm-mix technology. November paving makes everyone nervous, but we found it could be done.”
The narrow window
“We could only work within certain timeframes; we could not impact morning or evening rush, which doesn’t leave a very big daytime window in between, especially since anything we milled we had to have paved that same day,” said Casey. “We needed a big work window, which we got on overnights.”
While warm-mix asphalt (WMA) wasn’t the first choice for this project, its application at this juncture gave crews their best shot of getting the result they needed in the time they had to pave. Hanley Road is a variable-width artery that is primarily four lanes, but widens to five at intersections and as you approach the heart of downtown Clayton, where that fifth lane is a center-lane, bidirectional turn lane. On some parts of the project site, business were as close as 10 ft from the road, which added another challenge. Thankfully, the level ground in the area meant workers were able to achieve a consistent depth with relative ease. The existing pavement cross-section ranged from 2 to 4 in. of asphalt, beneath which was concrete. Subcontractors addressed a handful of full-depth concrete repairs, allowing Pace Construction to get down to the paving—and not a moment too soon.
All in all, they were looking at 50,000 sq yd of pavement placement, which would end up requiring 5,259 tons of asphalt. A single 2-in. lift was placed via a Blaw Knox 3200 rubber-tire paver running off an International 7300 distributor; this lift thickness itself reflected a last-minute change, as the initial planning called for a 1.75-in. lift. Once work got underway, however, engineers felt, according to St. Louis County Resident Engineer Scott Dezort, that extra 0.25 in. “gave us more stability, considering all the utility repairs, basically a better base to deal with. It’s not the kind of road you want to go back into anymore than you have to, given the traffic it gets.”
While the Superpave was executed on the mainline, the side streets were completed with a standard County C-mix that consisted of PG 64-22V binder, 12.5-mm nominal maximum size aggregate, and incorporated a percentage of porphyry aggregate as well as 20% reclaimed asphalt pavement—that percentage being a target threshold the county has on all its asphalt projects. The choice of mix was crucial for crews to achieve both quality in density and target compaction, notably since in November temperatures can drop after dark quite significantly.
“Both mixes allowed for temps to get down to 40°F,” Dezort told Roads & Bridges. “In fact, the lowest we got one night was 39°F. We kept the mat temperature at 295°F, as high as possible, and we had the rollers right behind the pavers to hit it straight away to avoid it cooling down.”
The asphalt plant was only 15 miles from the work site, so testing was easily completed both in the lab and on-site (coring) to assure that the mix was reaching the appropriate density. Compaction was the result of three vibratory passes with two breakdown rollers and a single static pass with a finish roller, all Volvo DD118 tandem steel-drum rollers.
“That’s really the happy ending to this whole thing,” Dezort said. “To say we paved at 40°F, got compaction and the average density achieved was 93.1%, that’s pretty impressive.”
Casey agreed. “The WMA extended the timeframe for compactibility, considering the temperature implications. You can compact it at lower temperatures, even if you lose heat a little more quickly. We started paving on Nov. 2 and went through Nov. 18. That was our last day.”
The manhole slalom
“This is a major corridor for the Metropolitan Sewer District and its main,” Dezort said. “So, we had a tremendous number of manholes we had to meet and adjust to grade. We had upwards of 65 manholes over a mile of road. Lots of water valves and gas valves, a lot of obstructions in the roadway,” making both the milling and paving a particular challenge.
“Lots of manholes and utility valves were in the way,” Casey said, “which was a milling issue. Plus it would be only in the upper-30s at night. And that stiffer oil was hard to manipulate once it was out of the paver. But we got it done. It was a very easy process with the group of people we worked with over there. We were all working toward the same goal. The road would have only gotten worse going through another winter, so we all wanted this done before winter, certainly not to stretch it into the following spring. The county was willing to explore the use of and pay for WMA.”
St. Louis County is looking to get 10-12 years out of the new Hanley Road, possibly 15 if luck is with them. This goal they attribute to both the skill employed by their contractor and the quality of the product laid down. “That 76-22 oil should get us well past 10 years,” Dezort said, adding, “It won’t be our practice to pave in November, but if we should ever find ourselves doing that, we’ll have a much higher level of confidence due to this mix design.”
As though the result of the fractured project timeline held some measure of wonder, despite the visual proof of the finished road, not to mention a 2015 Missouri Asphalt Pavement Association Municipal Paving Award, Jonas could only add, “Trying to get compaction in November, whew. But we’ve gotten good feedback from residents. No news is usually good news, so actual news is wow.” R&B