Rocky Road: Carving Roadways, Utility Trenches In Tough Rock

May 2013, Vol. 68 No. 5

“There is a fine line between pushing it and overdoing it,” says Merck. “Our trenching and milling operators are very experienced in these conditions, and have a great sense of feel for just how much they can safely get from a machine. Vermeer equipment is tough -- especially in rock -- which made possible for crews to achieve the 300 to 400 feet per day production rates we were able to realize.”

Culvert junction
Merck ran 16-foot trencher booms for the majority of the job; and on several occasions along the route needed every foot of the depth in order to make grade. In fact, at a few places along the route where the slope of the terrain extended beyond that depth, additional milling was necessary to accommodate the deeper trenching needs. At an average width of 2½-feet to accommodate the eight-inch sewer lines and 12-inch water lines, more than 25,000 yards of rock was excavated to complete the 60-acre site.

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Where the roadway routes intersected, it was necessary for Merck and crews to install box culverts to direct the flow of storm water drainage. Each culvert -- measuring five feet by 4 feet -- was cut into the rock using the track trenchers and a process Merck describes as ribbon cutting. “The widest we had to trench was to accommodate a concrete box for culverts measuring five-feet wide so the trench leading up to those ended up being approximately 8½- feet wide. This required ribbon cutting through the rock.”

“The biggest challenge was definitely the topography,” Merck says. “This area is known for how hard the rock is. You’ll catch flint in some of the stuff and mixed with the limestone, you can burn through teeth in a hurry if you don’t know what you’re doing and don’t take the proper maintenance precautions. We learn something on every project; out there, we’re continuously learning the rock. We’re going to have much of the same on our next project, so what we learned on the top of The Dominion we’ll apply to the next development.”

“Our guys are continuing to sharpen their rock trenching and milling skills, learning how to operate the equipment most effectively and efficiently,” Merck says. “It all comes with experience -- a sense of feel and knowing exactly what the equipment can handle.”