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The public (that group
for whose benefit we do most of our work) does not like mess and
disruption on the surface, and people prefer to have all their utility
hardware aesthetically hidden. So more construction than the public
imagines is underground.
There have been beneficial
advances in trenchless technologies in the last two decades, but
it would be inaccurate to say that all underground construction
is now done with trenchless equipment and techniques. It depends
on the trench. It depends on the ground. It depends on the path
that has been planned for the underground work. It depends on the
funding for the project.
Will it go under a railroad?
Under a stream or river? Under the interstate? Are there criss-crosses
of buried utility lines? Those are probably trenchless applications.
Does the trench provide space for a cross-country cable or pipeline?
Is the trench for cable and pipe connections at a new multidwelling
development? Are there few underground obstacles? Those are applications
where the machines called trenchers and plows will do well.
What is a trench? If
excavation is a hole in the ground, what makes a trench a trench?
It’s longer than it’s wide, usually. Sometimes it’s
only a few inches wide. Sometimes a trench is a yard or several
feet wide, and people work in it. If the trench is big enough for
a person to stand and work in, it should be shored against cave-in.
That’s basically what the law says, and any contractor who
does not shore a trench where his workers are active is committing
premeditated … You don’t need reminding of the risks or
moral obligations. Shielding and shoring for trenches protects workers,
equipment, and adjacent structures.
Basic Trenchers
If there are no underground obstacles like pipe and cable,
there are many applications where trenchers are the fastest and
most efficient solution. That’s why they were invented! Excavators
can make trenches, especially the larger varieties, but a trencher
is built specifically for making trenches, and it does it accurately
and fast. Machines that have always appealed to us for their simplicity
and practicality are the vibratory plow and trencher plow.
For a townhouse project
some 20 miles south of the international airport in Atlanta, GA,
Genesis Construction used a ride-on hydrostatic trencher/plow (Vermeer
RT650) to put a trench that ended up at about 45,000 feet in its
meandering length. “We’re trenching 6 to 8 inches wide
and 36 to 42 inches deep,” notes Paul Harrison, construction
supervisor for Genesis. “That’s a joint trench, with several
utilities going in the same one. On most days we trench a total
of 300 to 400 feet. On a more wide-open subdivision, where there’s
less congestion, we do about 1,000 to 1,500 feet per day.”
What do they do about buried utilities? Genesis contracted to do
the electrical, telephone, and cable at the site. The only other
utility on the scene before it was the water company. “The
water lines are in first, and that can pose a problem,” notes
Harrison. “If they have gone in deep enough, we can go over
the top, but otherwise we have to hand-tunnel under them. Sometimes
the water meters are already set, too, or they may just have copper
lines in. We just take it as it comes.”
It was water lines—about
67 miles of them—that prompted contractor Charlie Holub to
invest in a Trencor Maverick (now a T560, from Astec Industries).
That machine is a chain trencher; it can handle soil and rocks.
The new water lines were for Marion County, KS. They ranged from
2 to 10 inches, which was not especially difficult, but there were
those 67 miles. “Productivity was important,” comments
Holub, owner of Ditch Diggers and the man who operated the trencher.
On the first day he cut 2 miles, 3 miles on the next. “Of course,
it depends on how many obstacles we have to go around and how much
mud we have to fight,” adds Holub. “Right now, we’re
producing between 20 and 30 feet per minute, and that’s not
bad considering all the rain we’ve had here.”
Quite the opposite of
a 67-mile trench are those trenches required for utility installations
at many residential sites, not locations that involve an estate
for several houses, but ones where there are just one or two new
homes. Or you may be asked to install new lines to an existing building.
The trenches are short, and there may be little room for maneuvering.
That’s where walk-behind trenchers and plows have proved their
value. A trencher will dig a trench, while a vibratory plow will
lay the cable, too, as it goes along. Walk-behind trenchers (like
the 1030, 1230, and 1330 from Ditch Witch) have been successful
for water, sewer, gas, electric, and communications applications,
with trenches from 2 to 4 feet deep for the trenchers and 1 to 2
feet deep for the plows. A hydrostatic vibratory plow can go through
the garden gate to install power lines and telecommunications cable
up to 1 inch in diameter, or water service, sprinkler system, or
natural gas pipe up to 3 inches in diameter.
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PHOTO: BOBCAT |
Let’s look at some
of the features and benefits mentioned by one manufacturer. We won’t
tell you who it is, but the points mentioned will give you a good
idea of what to look for in any trencher:
- A high-horsepower
engine for a small machine
- Two speeds and four-wheel
steering
- Attachments available
to complete many underground jobs
- Direct-driven hydrostatic
transmission
- Infinitely variable
speed ranges within given parameters
- Oscillating front
wheel axle to maintain contact on uneven ground
- Backfill blade (with
all six functions from one control)
- Unitized main frame
to absorb shock loads
- Easy access to all
areas of the unit
- Heavy-duty trencher
attachment, planetary chain drive
- Trencher chainline
reversible to dislodge from obstruction
- Dual open-end augers
to move spoil to both sides of trench
- Trencher speed infinitely
variable to adjust to changing soil conditions
- Worker safety restraint
bar as standard equipment
- Vibratory cable plow
system that avoids damage to cable when blade is lifted
- Generous offset (32
inches) for blade from centerline
- Mounting of shows
allows work next to walls and other obstacles
- Plow has hydraulic
lift, down, and swing pressure
- Backhoe attachment
available
The list could be much
longer, but you can imagine the importance of apparently small features.
Some of your best advice could come from other contractors who have
experience with different trenching machines and techniques. Ask
your manufacturer/dealer for references and application stories
from contractors who do the same kind of work you want to do.
One thing you may have
noticed is that the leading companies in trenching machines are
leaders in trenchless technologies, too. Their expertise is in the
design and manufacture of practical equipment for virtually all
underground construction projects. You would usually obtain their
equipment from networks of dealers in strategic parts of the country,
an important consideration when it comes to advice or service for
your trenching applications.
We came across many names
of manufacturers of equipment for trenching. The list could include
those who make self-contained systems and those who build attachments
for other carriers. One caution we were given by several contractors
was to make sure that the machine purchased or rented was intended
for professional, frequent use. In a sector related to trenchers,
we were advised that the tiller made for your personal use was not
the same as the tiller intended for commercial or professional use.
Without any intention
to endorse or comment on anybody, here are some of the names most
mentioned in the smaller trencher market: John Deere, ASV, Vermeer,
Toro, McCullough, Barreto, Caterpillar, Ditch Witch, Daewoo, Case,
Polaris, Parsons-Maxon, Ramrod Equipment, Kanga Loaders, Bobcat,
Kubota, Ground Hog, Trench Master, Brown Manufacturing, EZ-Trench,
Power House Equipment, Z Loader, Pengo, CEAttachments, and JCB.
All those companies seem to have Web sites with varying degrees
of product information available.
Rocks and Hard Places
Then there are the big trenchers. When the ground is rock and
you have to make a trench to carry pipe for a few miles, good productivity
is essential to good profitability. The walk-behind trencher will
not cope with a cross-country trench through ground that contains
rocks of varying hardness. A powerful excavator could make a trench,
but not one as clean and fast as the right kind of trencher.
C&S Co. is based
in booming Las Vegas and has received contracts for the installation
of sewers, water lines, storm drains, streets, and curbs for a community
called Mountain’s Edge, on the southwest side of the Nevada
city. The crews were doing 1,200 to 1,500 feet a day for some 24-inch
water lines (using a Vermeer T1055 hydrostatic trencher). Then they
struck basalt. “I got a phone call telling me they had gone
from production of 1,200 feet a day down to 200, and we couldn’t
figure out what was going on,” recalls Brad Lindburg, owner
of C&S Co. “That was the hardest stuff I’ve ever seen.
It was like granite.” Here’s where a local source of help
makes a difference. Lindburg contacted Vermeer Sales Southwest.
John May, the local representative, optimized the control settings
on the trencher and changed its tooth patterns. Production was back
up to 700 feet a day through rock that Lindburg called some of the
worst he had ever seen.
Highway drainage projects
are sites where you may see rocksaws or chain trenchers in action.
State departments of transportation have different requirements
for edge drainage. For a PVC pipe project, a chain trencher is preferred
by many contractors, with a rocksaw popular for panel-drain applications.
Trencor makes both kinds of machines; the company makes a vertical
cut between the pavement and the shoulder to depths as much as 36
inches and widths up to 15 inches. “We do more than a million
feet of highway drainage each year,” comments Tom Arnold, owner
of Tom Arnold Contracting in Carthage, TN. That’s almost 200
miles.
Tennessee uses regular
PVC aggregate pipe and filter cloth for its highway underdrain system.
“One feature of our Trencor equipment that has proved valuable
is the side-shift. We have many new construction jobs where the
underdrain has to go right up against an existing bare wall. At
other times, on rehab jobs, there’ll be an older two-lane road,
and we’ll have the underdrain scheduled to go right up against
the existing asphalt. That’s where the state wants it, and
we wouldn’t be able to put it there with that Trencor side-shift
feature. We’ve found that, with another machine, the closest
we could get from the existing roadway would be 42 inches.”
“On highway-edge
drain projects, the work is split about 50-50 between rehab and
new construction,” observes Pat Beasley, general manager of
Beasley Contracting in Tupelo, MS. “We specialize in this kind
of work and we’ve completed projects in Florida, Alabama, Louisiana,
and Arkansas, even as far over as New Mexico.” Beasley also
uses Trencor equipment. At Central Illinois Tile Co. crews use a
Trencor rocksaw and a regular trencher in combination. “We
specialize in the installation of drainage on interstate highways,”
explains Bill Schlueter, a partner in the company. “The rocksaw
cuts through the asphalt or the concrete base, and a regular trencher
helps us go down and lay our round pipe. We laid 10 miles of Monsanto
drainage mat in one day! Our installation crews normally work about
40 to 50 feet per minute and average 3 to 5 miles per day.”
Everyday Problems
for Some Contractors
If you live in a kind, balmy climate like Florida or California,
you seldom consider the problems caused by frost. In some parts
of North America, the frost can settle as deep as 6 feet below the
surface. If there are clay soils, they can make the ground swell
or shrink as water comes into contact with the soil. That can cause
serious movement problems with a home’s superstructure.
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PHOTO: VERMEER |
In northern Alberta,
Canada, for example (around the Edmonton neighborhood), pilings
are used to secure foundations and for securing attached garages.
One contractor found that his skid-steer loader, with an auger attachment,
was perfect for doing the preliminary work. He used his Mustang
2105 skid-steer loader and a 16-foot, 40-gallon-per-minute auger
attachment to increase his augering speed by three minutes per hole.
“That may not sound like much,” says Harry Verkuyl, owner
of H.E.C. Foundation Piling in Edmonton. “When I started drilling
for foundation pilings, it took four to six hours to drill 20 holes.
After experimenting with various augers and bits, I was able to
get the drilling process down to 30 holes in one hour. I credit
the equipment I use for that.” Of particular benefit has been
the high-flow hydraulics system on the 2105. This, along with the
unit’s adjustable flow valve, has allowed Verkuyl to adjust
the amount of hydraulic fluid directed to his auger attachment.
Skid-steer loaders can
have trencher attachments; they have proved popular for trench work
near buildings and fences when they offer a manual or hydraulic
side-shift capability. Even those small skid-steer loaders (like
Bobcat’s LT112) can achieve impressive productivity. The trenching
widths available for attachments on skid-steer loaders range from
4 to 12 inches, depending on the carrier, with flow ranges from
9 to 32 gallons per minute. The digging depth capability for these
trencher attachments varies from 24 to 60 inches; you can see how
good productivity is achieved. Ask the loader manufacturer or his
dealer which trencher attachments are suitable for your machine.
Before acquiring, by purchase or rental, an attachment that will
do your trenching you must be sure that your carrier has the hydraulics
necessary to run the attachment efficiently.
Caterpillar offers several
trencher attachments for its skid-steer and multiterrain loaders,
with the T6B the smallest of the family. This has a 36-inch boom
for those applications where you don’t need the greater depth
of the T9B or T15B. You don’t need high-flow hydraulics for
the T6B; it is designed to work with standard-flow hydraulics. The
direct-drive motor will give a good balance of torque, chain speed,
and chain pull, and this attachment has worked well in a variety
of soil conditions. The adjustable boom lets you have cutting widths
of 6, 8, 10, and 12 inches. If your work is close to structures,
the optional manual or hydraulic side-shift will make that a simple
task, with a maximum side-shift of 22 inches to the right of center.
Caterpillar offers 21 different chain types and width configurations
for the trencher, with installation done for you at the factory
before delivery.
One problem you could
face at some sites is how to get your equipment to the place where
you will be working. TT Technologies offers a compact HDD trailer
rig on which you can transport a Grundodrill 4X compact HDD and
a Grundomudd DS 225 bentonite mixing and delivery system. The trailer
comes equipped with stem racks that can hold up to 32 extra drill
stems (160 feet). That Grundodrill 4X was specifically designed
for the installation of conduit, as well as those residential services
with small-diameter main installations.
Sometimes it is the site
itself that limits your equipment. Access and depth were the challenges
for Welbro Building Corp. for a project at the Nickelodeon Family
Suites of Holiday Inn in Florida. The vaults for “The Lagoon,”
a water park and interactive playground, were scheduled to be 9
feet deep. That would usually mean sheet piling or a trench box.
With the courtyard’s limited access (basically, a 10-foot square
tunnel through buildings), sheet piling would have to be craned—blind—over
the buildings, and a properly rated trench box could pose dangerous
conditions.
The contractor decided
to install three personnel-accessible water vaults to a depth of
7 feet, with 2 feet above ground to be camouflaged by creative landscaping.
Getting the approved pit-shielding system into the courtyard was
still a challenge. The solution was a modular Build-A-Box trench
shielding system from Efficiency Production. The manufacturer designed
special configurations for this trench/pit project, and all the
components could be hand-carried into the hotel courtyard. The results
were most satisfactory. The only heavy equipment used comprised
three trackhoes (two IHI, one Bobcat) and one TCM frontloader; they
all could travel through the access corridor.
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PHOTO: EFFICIENCY PRODUCTION |
Replacement of Existing
Pipes
If there are obstacles for your underground construction—such
as rivers, railroads, and highways—trenchless techniques have
proved their worth. If there is one sector of trenchless technologies
that seems to gain momentum annually, it is pipe bursting. This
is where the current pipe is broken and the new one (usually bigger
for an upgrade of capacity) pulled through, without digging up (or
having to backfill) long trenches. The debris is left in the ground.
An interesting innovation
has been a 16-inch Air Impactor pipe-bursting tool from HammerHead/Earth
Tool. With this system, a hammer is activated when pull force is
applied to it and, when the pull force is stopped, the air supply
vents, shutting off the hammer. “This pneumatic method is excellent
for modest up-sizes in sanitary sewer in reasonable ground,”
notes Steve Wentworth, vice president of advanced product concepts
at Earth Tool Co. “Static rod-pulling machines and their equivalents
are high tonnage with no dynamic impact energy superimposed over
the static force. Static lends itself to modest-size water pipe
replacement.
“A hybrid method
has some of the best qualities of each while still being capable
of handling more adverse conditions in the ground and multiple up-sizes.
This middle-of-the-spectrum process takes the easily handled and
operated midsize rod puller with enough tonnage to ensure that pipe
friction will not be an issue. It gives it the self-adapting ability
of dynamic impact.” The average force of the hammer will increase
as the going gets tougher. If an underground obstruction (such as
concrete over a patched area) is met with a hybrid system, the static
machine can max out, but the hammer will carry on making useful
progress.
Several companies manufacture
pipe-bursting equipment. As mentioned, the leading companies in
trenchers are also those in trenchless technologies and they have
helpful, informative Web sites. Whatever your underground construction
challenges, there are many good products to help you complete the
task safely and profitably. It will take a little homework and research,
but the time spent will be worthwhile.
Paul Hull writes on
construction and environmental topics for several international
magazines.
GEC
- September/October 2005
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