Underground Construction - August 2021 - 30

SPECIAL SECTION: Vaccum Excavators
Vacuum Excavators for Utility Construction:
Air or Water?
Jeff Griffin | Senior Editor
Vacuum excavators are a common sight on utility construction
project sites today.
These dual-purpose machines can make " soft " excavations with
either high-pressure water or air and also are a powerful vacuum.
For utility construction, their value primarily is potholing -
digging a small hole (about 12 inches square) to uncover existing
utilities and visibly confirm their location before soil is displaced
by new construction. They are also used for cleaning up drilling
fluids that escape from bore holes during horizontal directional
drilling (HDD) to install new pipe or conduit.
Vacuum excavators' capabilities certainly aren't limited to these
applications - they can make precisely controlled excavations for
virtually any purpose and are effective for general job-site clean-up
and special applications.
Their value for digging is being able to make small excavations
that limit surface disturbance. For potholing, soft excavation is
much less likely to damage the utility being exposed than mechanical
methods such as backhoes or compact excavators.
However, there remain concerns over which type of vacuum excavation
technology is best for specific applications: air or water?
There are vocal proponents for both methods and representatives
of two manufacturers shared their views on this topic.
Hydro
Vacall manufactures large, truck-mounted hydro (water) excavators.
Vacmasters is recognized as a leader in equipment that uses
high-pressure air to excavate.
Vacall Product Director Tod Ebetino said hydro excavation is a
much faster process than air, but at times it can be very messy.
" Loads become heavier faster with water and require transportation
to a dump site, " he said. " Water excavation also requires
additional backfill that needs to be delivered by additional
equipment and manpower. All of this can result in higher overall
costs on the project. "
Excavating with air, he said, allows the operator to dispose of
the spoils onsite. This eliminates costly trips to a dump site, which
generally charges a fee.
When comparing the two methods of excavation, hydro
proponents generally say air excavation is not effective in some
soil conditions.
Hydrovac model
" Compacted clay or rocky soil conditions limit the digging
effectiveness of air excavation, " Ebetino said.
All Vacall equipment can excavate with water or air.
Vacall AllExcavate machines are built on severe-duty truck
chassis and offer superior load distribution and filtration, thereby
delivering highly productive and safe machines, Ebetino said. All
models are capable of pulling vacuum up to 27 inches hg at 5,800
cfm water pressure for hydro excavation to 25 gpm up to 3,000
psi, and air excavation at 185 cfm and dual psi of 110 and 150.
Gradall Industries manufacturers the Vacall AE machines
with 10- or 12-cubic-yard debris tank capacities and 1,000- or
1,300-gallon water tanks; all available with optional air excavation.
Air
Since the time vacuum excavators began appearing on utility job sites,
Vacmasters has been a primary provider of air excavation equipment.
" All Vacmasters systems today can excavate with air or water,
but our customers find that they are able to dig with air 95 percent
of the time, said Vacmasters Sales Manager Charles Bell.
" Comparing operating and initial costs, " Bell said, " an air system
carries less water and the ability to re-introduce displaced soil at
the job site saves contractors money on disposal fees and hauling
cost for new backfill.
Air model
30 AUGUST 2021 | UCONonline.com
" Scaling down the water supply and having smaller spoils tanks,
provides a more cost-effective method for locating utilities with
a lower initial cost of the unit and lower operating costs, " he
continued. " Digging with air also increases billable hours - as long
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Underground Construction - August 2021

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