Urban Digs: In the Trenches
Trenching can take a little longer than blasting, but it does a neater job.
Limestone, the rock lying under 6 to 8 inches of Tennessee topsoil, typically
requires blasting, but where blasting is prohibited, Eddie Conrad, owner of
Conrad Construction Co., says trenchers are “handy.”
Fort 35 years,
the family business with 33 employees, located in Nashville, TN, has specialized
in building roads and infrastructure—primarily water and sewer lines. Conrad,
who does $3 million–$4 million in business annually, has put in water and sewer
lines to the cities of Lebanon and Hendersonville and works for various
“We used to
blast,” Conrad admits. “It made life easier.” However, the threat of litigation
from potentially damaged homes and businesses complicated the ease of blasting.
Because the rock is weathered, Conrad explains, a blast can cause fissures or
caverns—and the resulting shock waves often do additional damage.
Conrad more often uses a Vermeer trencher to do the job. “Trenching takes longer
than blasting, but it does a neater job.” How long it takes depends on the
rock’s density. Hard rock cuts better than dense rock.
Trenching Versus Blasting
Conrad’s opinion that trenching takes longer, in many situations, trenching can
be the quicker, more efficient option. Although blasting through hard rock was
long considered the favored way of excavating for a pipeline, contractors across
North America are discovering, as Conrad has, that trenching offers many
disturbs nearby structures and fractures the rock, but trenching cuts a smaller,
neater path, with less ground disturbance. That also reduces liability.
material for backfill is typically needed when blasting. Cutting through several
layers of soil in a single pass, a trencher excavates the spoil, which can often
be used as backfill material.
results in irregularly shaped walls requiring additional excavation. Irregular
walls resist compaction. Trench walls are vertical, minimizing excavation, and
have consistent dimensions. Uniform walls aid compaction. The flat-bottom trench
is straight, at a controlled grade.
a wider opening that requires more surface patching—and at greater cost. In
addition, as the surrounding structure settles, surface sinking can occur. A
small opening at the top of the trench conserves patching materials and reduces
the amount of finishing required.
increased when trenching in close proximity to other infrastructure or in urban
settings, once again reducing the risk of liability.
“Safety is 90%
of getting the job done,” Conrad states. “If the job kills you, there’s not much
profit.” He is able to safely cut a ditch up to 22 feet in depth in the vicinity
of high-pressure gas mains. The trencher leaves a “slick-face rock when cut.
It’s a safe place. Even OSHA recognizes the safety of a rock wall.”
Because of the
increased focus on environmental issues and a growing number of restrictions and
regulations, rock trenching is eclipsing blasting and hammering, both of which
can produce unpredictable results, often at greater cost.
|Trenching eliminates many of the liabilities associated with
blasting, including increased insurance.
customer, Dave Rice, owner of Las Vegas–based Rice Construction Co. Inc.,
prefers trenching to blasting because it produces rock smaller than 1 inch in
diameter that can be used to fill the ditches. He’s also happy that production
increased by nearly five times when he replaced a 60-ton, 400-horsepower
trencher with a Vermeer T1255 Commander. Not only is it the largest production
track trencher available, the 90-ton unit puts out an additional 200
horsepower—essential, Rice says, for cutting through stone and caliche in the
residential areas of southern Henderson, NV.
installed a 10-inch water main approximately 13 feet deep throughout the
623-acre development at McDonald Ranch called the Canyons. His previous trencher
got 30–40 feet per day, but he reports getting 10 times that amount with the
T1255. Equipped with the Vermeer Trencher Electronic Control (TEC 2000) system,
the T1255 is automatically adjusted to varying conditions.
offers many desirable advantages for all contractors. It eliminates many of the
liabilities associated with blasting, such as increased cost of insurance,
bonds, and permits due to higher safety risk; additional debris and hauling;
risk of high rock explosions; intrusive method that isn’t permitted everywhere;
additional filling material and backfill requirements; increased wear and tear
on equipment; and limited access. Other benefits offered by trenching include
low environmental impact and increased speed and efficiency. A precise,
controlled path can be cut, and, because other crews can continue working
simultaneously, trenching saves time and money.
Choosing the Right Equipment
environment for trenchers is tough, rugged, and dirty. It’s imperative to match
the equipment to the conditions and meet the demands of the job. Equipment
features to look for include durability, flexibility, reliability, efficiency,
economy, and operator comfort. Urban projects require additional maneuverability
and add to the shopping list of necessary features.
60-horsepower RT55 is designed for the toughest, tightest landscapes, says Greg
Adkins, trenching product manager for Ditch Witch in Perry, OK. Equipped with a
quiet Deutz engine, the compact, powerful, versatile trencher works efficiently
in urban settings.
which sells 50% of all trenchers worldwide, invented the first walk-behind
trencher in 1949. It all started with the local plumber, Adkins explains, and
getting him from the street to the house. Today, the company caters to
contractors, municipalities, water and sewer companies, and rental yards with
its three main product lines: trenchers, ploughs, and hydraulic saws, all
for urban jobs is the RT115, a 4WD turbocharged heavy-duty tractor featuring a
115-horsepower John Deere engine and hydrostatic transmission, although Adkins
says it’s also available in a power-shift version, a unique feature. “Most of
the industry uses hydrostat or mechanical for performance efficiency,” he
The HT115 is a
hydraulic-track version of the rubber-tired powerhouse. Its one-piece rigid
frame design increases capacity and endurance. An optional tilt-frame
configuration assists in digging vertical trenches on uneven ground. Dual
steering helps in “crabbing” on slopes to maintain a better plow path and to
keep from drifting down. It’s also available with a rear-steer option that
enables tight turns for urban settings.
the key to the market, believes Tony Bokhoven, track solutions specialist with
Vermeer Manufacturing Co., and is driven by competition with the excavator
market. But while he says Vermeer is looking for additional capability, he
cautions, “We’re not trying to build a Swiss Army knife. We’re trying to get the
machine to be more versatile but not be everything.”
|Photo: Ditch Witch
|The 60-horsepower RT55 from Ditch Witch is designed to operate in
the toughest landscapes.
From the 755 to
the 1455 (the largest available), Vermeer’s hydrostatic trenching units offer
high torque and horsepower, can dig to deeper depths, and feature flexibility
for varying work conditions. The large head-shaft motor is designed to produce
full horsepower all the time. Hydrostatic transmissions engineered by Vermeer
deliver high torque without losing horsepower due to torque converters.
Able to operate
at full load at any chain speed, durable, heavy-duty track chains can operate at
a range of cutting speeds, allowing an operator to match the machine to the
conditions. Vermeer provides customized baseplate configurations and has
developed a digger chain specifically for trenching applications.
play an important role in getting the job done. Ditch Witch offers several
attachments for its line of ride-on tractors for contractors. A chain saw for
the trencher cuts to specific depths and widths. Vibratory ploughs are useful
for cable and waterline drops. “We developed cut-tooth technology on our digging
chain. The blade goes in the ground 2 to 4 feet,” Adkins says. “As the blade
cuts, the vibrator vibrates the blade to put the product in the ground. It
creates less disturbance in the earth.”
depths of 18 to 36 inches. Rock bits on the cutting wheel chew through asphalt,
concrete, and rock. “There are many chains available for a trencher; the cut
tooth is for dirt only,” he says. “The rock chain is for rocky conditions; it
has a carbide tip rock bit.” There’s also a combination chain.
offers mechanically driven digging attachments. Adkins points out that most
brands use belts and gears. “We use a torque converter to give mechanical
efficiency with the flexibility of hydraulics (fluid coupler). Contractors like
mechanical-driven. Hydraulic is user-friendly, but it’s the least efficient.
Utility companies like it.”
recognizes the importance of easy plug-in, plug-out versatility. When the 1250,
for example, costs $1.7 million, “you need the ability to convert it to a
trencher to continue to use a tractor,” Bokhoven says. That’s why the same boom
head holds all attachments. “It’s a unique feature,” he states. “For the
upper-end 850 and up, attachments are interchangeable between the trencher and
the train leveler without huge modifications to the machine. It increases
|Trenches must be shored while contractors are working. Slide-rail
systems can go where others can’t.
working on a new bucket wheel attachment for the T655 Commander 3, popular for
wind farms and cross-country gas pipeline applications where the ground is
hardpan cobble. Bokhoven says their focus is currently on the bucket wheeler,
versatility and ease of use.
Vermeer is concentrating on include productivity and operator comfort. “We
stepped back to make our machines more productive,” Bokhoven relates. One step
toward that is the introduction of the T1155 Commander 3 trencher, which can
reach greater depths and widths. But for current models, that step involves
adaptation to Vermeer’s TECplus system. The company’s exclusive, patented TEC
2000 and TEC 2000.2 control systems monitor operating conditions, increase
productivity, and reduce machine wear. In addition to providing an integrated
electrical system for automated control, they also work as diagnostic tools.
1,000 feet of wire out of the machine,” Bokhoven states. “It had a big wiring
harness; that was troublesome.” Vermeer also positioned multiple computers
around the equipment in order to more easily detect issues. “We can zero-in
quickly. That cuts down trouble-shooting time and is more efficient. The
operator can give the information over the phone to tech support and get
problems resolved quickly.”
also sought to enhance the experience in the cab in order to go after the
excavator market. Attention has been paid to operator comfort: air-ride seats;
an ergonomically designed, bigger cab; and a larger screen on the dash that’s
easier to see and simpler to operate. Elevating and extending cabs and placement
relative to the digging boom are designed to provide the operator with better
visibility. Another important aspect, Bokhoven believes, is that operations are
consistent. “There’s very little time to train operators to cut ditches
efficiently, so the controls are the same in all Vermeer machinery.”
the smallest walk-beside Ditch Witch machine to the largest, the operator
controls are color-coordinated the same way. “Every feature is color-coordinated
on all the machines, no matter the size,” Adkins confirms. “That way, as people
switch from one machine to another, they know where the controls are. It’s a
safety feature as much as a convenience.”
Safety is an
important issue, but operator fatigue “is a very big issue,” Adkins continues.
“The balance of the machine is extremely critical so the machine takes abuse,
not the operator.” Their trenchers accommodate kickback when they hit rock,
softening the impact on the operator. Ditch Witch offers other user-friendly
features like cruise control to let the operator maintain and monitor
Service After the Sale
service is as important as finding the right features. Because Conrad started
with an “old 800 Vermeer trencher in early 1980s,” his expanded fleet consists
solely of Vermeer products. “My policy is it’s easier to maintain one brand; you
dance with the one who brought you. Trying to master the mechanics on one brand
is easier than starting with other brands.”
to talk about “value-added services that aren’t steel and engine,” such as the
company’s rock lab. “It’s a valuable tool that lends credibility to the numbers
we generate.” Rock sampling is a proprietary, free service for Vermeer customers
who send in rock from a job site. Vermeer takes core samples, tests them, and,
using their solutions calculator, figures the machine cost. “It narrows down the
costs for a more accurate bid. Contractors need to know the condition of the
rock to make an accurate bid and select the proper equipment for the job.”
recommends talking to equipment dealers in the area about local conditions. “In
a lot of areas, you run into multiple ground conditions. Use your local [Ditch
Witch] dealer; he knows the local ground conditions and can recommend the right
equipment.” For instance, in dusty/dry conditions, a dealer might advise putting
on a heavy-duty air-filtration system. Ditch Witch offers secondary filters on
smaller units. When an air-cooled engine is close to the ground, Adkins says,
a perennial after-the-sale concern. Adkins says routine maintenance on Ditch
Witch trenchers is simple and minimal. There’s no daily maintenance for gear
bushings, unlike steel bushings, which need grease and daily flushing because
they attract dirt. Some machines, like the RT95 power-shift tractor, offer a
“huge advantage” to contractors through the elimination of belts (wear items)
and the mechanical transfer of power. “The cost-saving performance of our
machines improves productivity and consequently reduces dollars per foot.”
to be shored while contractors are working. A slide-rail system from Efficiency
Production Inc. in Mason, MI, goes where other systems can’t, claims James
McRay, marketing. “It’s an alternative to tight sheeting. Traditional excavation
with vertical walls is tight sheeting; it requires special machinery to pile or
vibrate into the ground, which might be prohibited near hospitals or historical
areas. The slide rail system works well around utilities, buildings, railroad
tracks and other structures.”
America, it was refined based on the needs and job conditions of American
contractors. “We thought through different situations, installation projects,
and applications,” McRay explains.
He calls it the
most flexible, easiest system to install. The steel component system of panels
and posts is put together one piece at a time. Lightweight and adjustable, they
can be sized in any configuration.
The pieces are
manageable, take up less space and can be handled by midsize excavator and two
or three operators. “There’s no need to rent bigger equipment to lift it.”
three basic systems:
- The four-sided pit expands to up to 20 square
- The clearspan system can be configured in
infinite sizes up to 64 feet by 50 feet. “There are no cross-members,” McRay
says. “It’s an open excavation area … or a huge lift station.”
- The linear multiple bay system consists of
flexible cross-members for working next to utilities. The parallel beams with
24-foot rollers are highly reusable, as they “leap frog” over new sections.
contractors prefer an unobstructed field, McRay points out, but it’s not always
possible. “It’s more and more rare, especially as contractors get involved with
updating and repairing infrastructure.” But, he concedes, there is more and more
of this type of work in our shrinking world.
contractors are turning to these rail systems because a shored trencher pit is
safer and these can be installed and removed faster than any other shoring
system. In addition, the steel construction provides a long life, and the
installation creates only minimal vibration, so they are highly adaptable to
urban or other sensitive areas.
Writer Lori Lovely focuses on topics related to transportation and technology.