A fleet of Wirtgen W 2000s are keeping scheduled resurfacing of major streets in Aurora, CO, on track, and its motorists on the move.
Six W 2000 cold milling machines from Wirtgen America Inc. comprise the heart of the fleet owned by Alpha Milling Company in Denver. Of them, two have been delivered in 2005. The W 2000s figure prominently in Alpha’s strategy for serving Aurora and its many other municipal and county customers in Colorado.
Aurora’s Resurfacing Program
Aurora maintains an ongoing street resurfacing program coordinated through a pavement management program.
“We try to maintain our roads in at least a good-to-excellent condition for the traveling public,” said John Johnson, pavement management coordinator, Street Services Division, city of Aurora, CO. “This year we are maintaining a $7.5 million program, and we will do close to 120,000 tons of hot mix asphalt overlay. About 30,000 tons will be new stone matrix asphalt [SMA] technology for our major arterials. We use our pavement management program in conjunction with visual inspection to program our work.”
SMA is a gap-graded (low medium-sized aggregate and fines) hot mix asphalt (HMA) mix which combines strong, coarse aggregate with a high content of asphalt cement, as much as 6 to 8 percent liquid asphalt. The result is a strong HMA mix incorporating a stone-on-stone skeleton that resists rutting. The stone-on-stone contact develops internal friction and resistance to shear.
Because the gap-graded SMA lacks medium-sized aggregate, the low-penetration grade asphalt used conventionally can drain out of the coarse aggregate skeleton. This “drain-down” is precluded by use of cellulose fibers or other asphalt modifier to hold the binder in place. The percentage of fines is less than in conventional U.S. mixes, about 15 percent of the aggregate weight.
“We started three years ago placing SMA on our east-west and north-south arterials,” Johnson said. “It’s been very successful for us, we really like it. And as its use increases around the metro area, numerous plants are making it now and contractors are able to place it.”
Maintaining the Account
“The Aurora account is one we’ve had since 1990, except for a few years where a competitor beat us out," said Larry Ware, president, of Alpha Milling. “It’s a very large project, because this year Aurora will mill over 1 million square yards of pavement, just for one city.”
Alpha also coordinates trucking, brooming and cleanup on the Aurora account. About 40 percent is subdivision streets, and the remainder is arterial and collector streets, where a 2-inch mill is performed ahead of overlay. Alpha serves as subcontractor to paving contractor Lafarge West.
“The toughest part of this project is that on the arterials and collectors, we can only work 9 a.m. to 3:30 p.m.,” Ware said. “We have to put up barricades at 9 and be completely striped and swept by 3:30, or we get into a large penalty.”
Not necessarily on the same day, a prime contractor will patch and crack seal the base prior to placement of an asphalt overlay.
“I’m usually up ahead of the pavers,” Ware said. “Usually it takes two pavers to keep up with one W 2000 milling machine.”
In Aurora, depth of the milling will vary by project.
“If it’s a reconstruct in a residential area, we will mill to take all the asphalt out,” Johnson said. “A lot of the residential areas were built with the old 6 inches of base course and 2 inches of asphalt. After they’ve gone through 10, 12 years of use they’re pretty much deteriorated, and if we try to mill an inch off, there’s nothing left. We will have Alpha scalp the entire section off, with a bit of the base course, and try to get a minimum of 3 inches back in. That way, with the extra inch, next time we come through we can mill off an inch and put a thin lift overlay on.”
The city of Aurora also owns a Wirtgen W 1900, which it uses on residential areas and for patching.
Longer Work Season
The continental climate of Colorado gives contractors a longer work season than might be supposed.
“We usually are down by Thanksgiving,” Ware said. “December gets pretty sparse, and we don’t get started up until March 1.”
And Ware subs traffic control out to dedicated contractors.
“I always exclude traffic control on my projects,” he said. “It’s very specialized work and a completely different ball game.”
In June, Alpha also was using a W 1200 F to cold-mill sections of busy Colfax Ave. in eastern Denver, some four miles from downtown.
According to Ware, the company rebuilt a short section of road with 18 different turn lanes that that needed to be milled into and around. Alpha performed a 2-inch cold mill, plus 4-foot-wide patching 8 inches deep. Aggregate Industries, the prime contractor, was responsible for the paving.
Work hours were confined to 9 a.m. to 3 p.m. due to traffic loads. The area being milled was heavily rutted, much due to shoving caused by buses at stops. But due to revealed conditions, Ware brought in a W 2000 to bring the pavement down 6 to 8 inches at the request of the owner, Colorado DOT.
Since he started his business in 1998, Ware has stuck with the Wirtgen platform. One of his first machines, a 1000 VC, still is used by Alpha, although its controls are considered obsolete by today’s standards.
That’s clear to the operator of the W 1200 F on Colfax.
“I came from running our old 1000 VC, so this is a big step up,” said Jason Figueroa, operator of Alpha. “The 1000 VC is manual all the way through.”
Ware uses it on mill-and-patch work.
“Sometimes I’ll put it on some of the big city jobs where the patching is 6 1/2 feet wide,” Ware said. “I’ll mill out small patches with it, and use it in parking lots and small trenches.”
Ware still uses a 1900 DC, and has a three-wheel W 500 used for miscellaneous work in trenches, parking lots, curb reveal and tapering edges on big jobs. But his business is built around his six big W 2000s; Alpha took delivery of its second W 2000 this year in June.
“It’s a very versatile machine,” Ware said. “I thought many times that I might go to bigger machines, but the 2000s are much handier. I’m limited where I can use the bigger machines; those call for night work or the big Interstate projects. But I do just as well with my 2000s. Sometimes I will put two, maybe three machines on one job; if I had a bigger machine it might sit from time to time, but my 2000s are always being used. If I don’t have a big project I can pop them into subdivisions and they stay busy.”
Uptime on the Wirtgen platform is a major reason Ware has stuck with Wirtgen.
“Wirtgen has proven to me that they are a lot better machine than any of the others,” Ware said. “No. 1, the drum is engineered so that if you hit a manhole, 15 minutes later you can be going again. With other machines you might be down three or four hours, welding it back up and putting it back together. And Wirtgen teeth last for a long time. They’re price-competitive and I’m getting ready to stock up again for the rest of the year. No. 2, they’re easy to maintain.
“It doesn’t take that much maintenance to keep them going each year, Ware continued. “I’ve been really happy with them.”
Alpha’s distributor is Faris Machinery Company in Commerce City, CO.
(This story appears courtesy of Wirtgen Technology magazine.)