Making quick work of 250 median grates

Asphalt Case Studies June 05, 2015
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Curtis Contracting Inc. (CCI), based in West Point, Va., is a large regional contractor, specializing in all phases of asphalt pavement design and construction. They’re experienced in a variety of projects, including the massive paving required for an Amazon fulfillment center in Chester, Va., and the installation of “Combat Training Breacher Walls” at Fort A.P. Hill near Bowling Green, Va.
 
The company recently learned about a new paving technique that saved a great deal of time and money on a design-build pavement rehabilitation of 12 miles (76 lane miles) of I-264 for the Virginia Department of Transportation (VDOT).
 
The challenge CCI faced was two-fold. First, the project included about 250 large median inlet grates (20 in. x30 in. and 30 in. x30 in., with grates weighing 80-90 lb and 150 lb, respectively. The second challenge involved multiple asphalt lifts required to complete the rehabilitation, totaling up to 6.5 in. of new pavement.
 
Since federal and state highway safety specifications called for no more than a 2 in. differential between pavement and other surfaces at any time, CCI was looking at raising 250 inlet grates multiple times during the course of the work. Conventional utility raising involving excavation and new concrete rims would have been expensive, labor-intensive and time-consuming. Also, due to all the removal and replacement of new asphalt, the work would have degraded the overall quality of the rehabilitation and could have led to additional lane closures.
 
CCI needed a utility raising solution that was faster and more convenient than conventional methods, a solution that didn’t degrade project quality and met VDOT standards. Fortunately, such a solution existed.
 
“We heard about this method at a project meeting,” said Assistant Project Manager Kirill Gorin. “A team member suggested inlet grate risers fabricated by American Highway Products. We looked into it, and decided they would work well for the almost 250 median grates we would be dealing with. We’re more than half way through the project now, have installed hundreds already, and they’re working out very well.”
 
American Highway Products Catch Basin Risers are made in the U.S. with American steel and are approved under the FHWA Buy America clause. Similarly, they’ve been approved for federal highway use by many DOTs, including VDOT. In essence, they’re sturdy steel risers, custom manufactured to precise dimensions, that fit snugly within original utility frames; the original grate is then placed back in the riser, now raised so that the top grate surface is at the level of new paving. The risers are typically installed just before lifts, so new asphalt fills in tightly around the riser to provide support. And since pavement never needs be jackhammered or picked out, that support stays in place for the life of the pavement.
 
American Highway Products risers can also be stacked; that is, a new riser can be placed within an old riser. This meant that inlet grates could be raised in stages so that grate levels were always close to road surface levels, and the driving public was never exposed to dangerous dips or exposed grate edges.
 
“Cost effective and easy to install”
“There are nearly 250 grates on our section of roadway that need to be raised,” Gorin explained. “Most of these grates are not on a uniform grade due to pavement settlement, damage, etc., which further complicated the raising process. This was also compounded by the nature of the paving process with multiple lifts of asphalt.  There were 4.5 in. and 6.5 in. thick pavements that required installation of risers during each 2 in. lift, and final surface. Ultimately, a differential in pavement greater than 2 in. cannot be allowed.”
 
This meant that some grates were being raised as many as three times during the paving workflow, and in some cases three risers were being stacked. This was not an issue, according to Gorin.
 
“These risers are cost effective and easy to install. Ultimately, various thicknesses of risers (which can be as thin as ¾ in.) gave us the option of adequately adjusting the height of the grate without creating a hazard; too high would not allow water to enter the grate and too low (2 in. below grade) is considered hazardous to the traveling public,” said Gorin.
 
CCI uses three-to five-man crews to raise inlets, but not because the risers themselves are difficult to install.
 
“Keep in mind, the risers are not the difficult part of raising grates,” Gorin explained. “The existing grates are the problem. The 20 in. x 30 in. grate weighs 80-90 lb and the 30 in. x 30 in. grate weighs approximately 150 lb. Therefore, having to pry and remove the existing steel grate is the most challenging part of the operation.”
 
In fact, the most important tool needed for the raising process is a 6-ft crow bar, for the leverage it provides when removing grates. Actual riser installation is as simple as cleaning the original utility frame and tapping in the riser.
 
Given the large amount of risers used on this project, the relative lightness, ease of storage and fast fabrication time were important factors. CCI was able to transport, and stack and store the risers conveniently, and orders are typically fulfilled within a week.
 
“The simplicity, different thicknesses (heights of raise), ease of storage and ease of install made the risers advantageous to our needs; especially due to the large number of grates and non-uniformity of the shoulder grades on our project,” Gorin said.
 
A final consideration was the green aspects of riser use; because pavement does not need to be chipped out and hauled to landfills, gasoline and landfill space is saved. American Highway Products risers fit well into sustainable construction initiatives.
 
The I-264 VDOT project is scheduled for completion in November 2015, by which time CCI will have installed 500-700 risers. So far, the firm is very happy with the results, and is likely to use the risers for future projects.

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