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by Jeff Griffin, Senior Editor
Carbon Calculator Determines Trenchless Benefits
T
The benefits of trenchless construction are calculator is designed to be used with typi- other values. Default fuel settings are based
well known – at least by the manufacturers cal utility line replacement projects for pipe on current Caterpillar engines.
of equipment/products used for trenchless two inches in diameter and larger. The cal- When all project information is entered,
construction and rehabilitation and the culator is the first and currently only tool the calculator estimates CO2 emissions for
contractors who use them. available that can compare carbon emis- open-cut construction for traffic, trucks,
Compared to cut-and-cover construction, sions of open-cut construction and trench- machines, pumps and material (asphalt,
trenchless methods minimize the amount less construction. gravel, fill) and provides the total CO2
of excavation required to bury pipe and ca- The Carbon Calculator can be accessed emission from the project.
ble, reduces damage to surface structures, on the NASTT-BC web site, www.nastt-bc.
cause less disruption of org. By entering basic project information, Results
traffic and other activi- the calculator estimates the amount of car- For our fictional test, open cut was project-
ties on and around job bon that would occur during open-cut con- ed to release 708.5 metric tons of carbons.
sites, and allow instal- struction and three categories of trenchless Savings using all of the trenchless meth-
lations to be made in construction: horizontal directional drill- ods were significant:
areas where excavation ing (HDD); sliplining and pipebursting; and
is impractical or impos- cured-in-place pipe (CIPP) lining, point CO2 Emissions CO2 Savings
sible. repair and grouting. O’Sullivan explained
A good case also can that methods are grouped in the three cat- HDD 35.4 637.8
be made that trench- egories based on the amounts of carbon Slipline/ 70.8 637.6
David O’Sullivan,
less procedures are they produce. Pipebursting
P.W. Trenchless more environmentally The calculator is easy to use. Simply enter CIPP 14.1 694.3
Construction friendly because they a project description and provide answers (Emission quantities are in metric tons.)
can reduce dust, pol- to questions about project details: surface
lution and noise, and make installations conditions; length and depth of backfill that O’Sullivan pointed out that the calculator
through wetlands and other environmen- will be required; size of pipe; whether dewa- showed impressive CO2 savings for our fic-
tally-sensitive areas possible. tering will be necessary and if so, number of tional project , but that it is relatively small,
The British Columbia Chapter of the pumps needed; traffic flow; distances from and that a higher percentage of savings can
North American Society For Trenchless project to sites to pick up new fill; and fuel be expected on larger projects which can
Technology (NASTT-BC) has taken the en- efficiencies of equipment to be used. amount to significant reductions in release
vironmental factor a step further, asserting of CO2.
The calculator then estimates carbon
that trenchless procedures actually reduces A tip for first-time calculator users: be
emissions for each method of construction
carbon dioxide (CO2) emissions compared sure to enter all information requested.
and projects carbon savings for each of the
to open-cut construction. Under the equipment section, we made the
trenchless methods.
Trenchless methods for pipe replacement mistake of deleting the default fuel efficien-
To try out the calculator,
projects can reduce carbon emissions from cies of machines we thought would be un-
created a “test” project that
78 to 90 percent, said David O’Sullivan, necessary on the project and the blank box-
required installation of 1,000 feet of 12-inch
past president and current board member es prevented continuing to the next step.
of NASTT-BC and president of P.W. Trench- diameter pipe to be installed beneath as-
phalt. Asphalt thickness, depth of backfill The program selects the equipment nec-
less Construction. essary to match project information, so
“Reducing the amount of open trench and depth of bedding were entered. Dewa-
tering was not required so no pumps were emissions from unnecessary equipment are
also reduces the amount of soil removal note calculated.
to dump sites and importing fill material needed. Daily traffic flow was estimated at
10,000 vehicles per day and six days of traf- O’Sullivan said the problem of carbon
to fill the trench, minimizing truck emis- emissions is drawing increasing attention
sions,” O’Sullivan continued. fic control were entered. Next were travel
times from site to an asphalt plant if old as- throughout the world, western provinces
phalt is to be recycled or to a dump site if it of Canada and many U.S. states. “By 2012,
CO2 savings cities in British Columbia by law must be
is not, and travel time from a depot where
To provide a tool to emphasize the signifi- new fill material is picked up for transpor- carbon neutral,” said O’Sullivan.
cance of CO2 savings, NASTT-BC has devel- tation to the job site.
oped a carbon calculator that estimates CO2 The calculator uses default settings for Initiative
“savings” by using trenchless construction fuel efficiencies and vehicles used for the The Western Climate Initiative (WCI) is an
compared to excavation. O’Sullivan said the project, but allows them to be replaced with organization devoted to identifying, evalu-
20 Underground Construction ucononline.com July 2008
ating and implementing collective and P.W. Trenchless Construction is one of the how trenchless reduces CO2 emissions, is
cooperative ways to reduce greenhouse most experienced trenchless contractors in one more benefit we can cite to advance the
gases in the region. WCI was launched in British Columbia, specializing in pipeburst- trenchless industry.”
February 2007 by the governors of Ari- ing and sliplining.
zona, California, New Mexico, Oregon and “We would like to see the day when FOR MORE INFORMATION:
Washington to develop regional strategies trenchless construction is the default NASTT-B.C. Chapter, (604) 505-2084,
to address climate change. A short time method of underground construction – not nastt-bc.org.
later, the governor of Utah and premiers an option to consider when site conditions P.W. Trenchless Construction Inc.,
of British Columbia and Manitoba joined make excavation difficult,” said O’Sullivan. (604) 580-0446, pwtrenchless.com
the Initiative. Montana joined in January “Using the carbon calculator to document NASTT, (703) 351-5252, nastt.org
2008. Other states in the U.S. and Mexican
and Canadian provinces are participating as
observers.
Recognizing that reducing levels of CO2
released into the atmosphere has a posi-
tive impact on the environment, NASTT-
BC contacted the University of Waterloo
about undertaking research focusing on the
quantities of CO2 reductions that can be ex-
pected by using trenchless construction.
Conducted by Dr. Mark Knight and
Rashid Rehan, the study demonstrated that
large amounts of CO2 are released due to
traffic disruptions during utility construc-
tion along major roads. Using information
available from traffic studies, it was con-
cluded that the reduction in CO2 emissions
associated with trenchless construction is
achieved primarily due to limiting disrup-
tion of traffic flow and shorter duration of
projects using trenchless methods.
With research documenting carbon sav-
ings by using trenchless methods, NASTT-
BC began planning ways to promote this
important benefit. The carbon calculator
was developed on assignment by fifth-year
engineering student Liz Creelman at the
University of British Columbia.
The calculator became available on the
NASTT-BC web site in January 2008.
Envisioned as a tool for preparation of
proposals by public works officials, consult-
ing engineers and contractors, O’Sullivan
said to date documentation developed by
the calculator has been used by two entities
for proposals submitted to provincial gov-
ernments for funding available for carbon-
friendly projects.
O’Sullivan said NASTT-BC is a multiple
disciplinary organization devoted to ad-
vancing the science and practice of trench-
less technology for the public benefit; to
develop standards; promote education,
training, research, development and infor-
mation; and to promulgate through public
forums the improvements and status of
trenchless technology.
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