March/April 2023 - 101

A regular column showcasing successful
best practices for sustainable foundations
FOUNDATIONS FOR A SUSTAINABLE FUTURE
700 lb (317 kg) of CO2 emissions,
another easy to remember number.
When you compare that with the
approximately 400 million cu yd
(300 million m3) of concrete used in the
U.S. last year, it becomes obvious that
saving, say, even just 1% of that volume
by more efficient design is much more
meaningful. That 1% volume reduction
would account for 2,800 million lb
(1,270 million kg) of CO2 emissions.
Or we could compare the light rail
Carbon Savings in Seattle
The Challenges
When it comes to sustainability, many
find it difficult to relate to derived
emission reductions when alternatives
are presented. So, the first challenge is
simple: how can you present some very
basic numbers to make it possible to put
emission reductions in perspective?
The second challenge is, what can DFI
do other than just talking about more
sustainable foundation design?
The Solution
The DFI 48th Annual Conference this
year is at the Seattle Convention Center,
which is some 14 mi (22 km) from the
airport. Assuming 1,000 attendees all
take a rideshare using a gas engine
between the airport and the convention
center, it would require 28,000 car mi
(45,000 km), which equates to roughly
28,000 lb (12,700 kg) of emissions (on
average, one mile of a travel by a
nonelectric car generates one pound of
CO2 emissions). That is an easy to
remember number, and the answer to
the first challenge.
But there is an alternative in Seattle,
where the light rail system connects
the airport with the city's downtown.
For some time now, this system has run
on 100% carbon-free electricity as it
uses exclusively wind energy - the
first major light rail system in the
country to go completely green. If 1,000
attendees of the annual conference take
advantage of this light rail connection
between the airport and the convention
center, instead of riding in gas engine
rideshare vehicles, we can quantify the
savings at 28,000 lb (12,700 kg) of CO2
emissions and address the second
challenge.
The Results
While 28,000 lb (12,700 kg) of CO2
emissions may sound like a lot, it is
the same carbon savings as about
40 cu yd (30 m3) of concrete, as one
cubic yard of concrete generates some
emissions reductions to those associated
with rebar steel, where every
pound (since this kind of steel is usually
95% recycled) produces roughly 0.7 lb
(0.3 kg) of CO2 emissions. So, the
28,000 lb (12,700 kg) of emissions
savings from using the light rail would
be roughly the equivalent of saving
some 29,500 lb (13,400 kg) of steel.
When you compare that with an
estimated 20 billion lb (9 billion kg) of
rebar used in the U.S. last year, it is once
again clear that saving just 1% of steel
rebar weight is much more efficient.
While opting to use the light rail to
attend the annual conference may not
generate the same results as a minor optimization
of a foundation, it still makes
a difference. Hopefully many of you will
make your way through the parking
garage at the Seattle airport to the light
rail station for this year's conference.
Equivalent of 28,000 lb (12,700 kg) CO2
emissions: charging 1.5 million cell phones or
the annual electricity use in two and a half
houses
AUTHORS Gerald Verbeek, Allnamics, with contributions from Andrew Verity, Terracon, and Kimberly Martin, Ph.D., P.E., Keller North America
DEEP FOUNDATIONS * MAR/APR 2023 * 101
March/April 2023

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