Underground Construction - August 2021 - 17

Taming a Mammoth
feet from the southern edge of the open shaft, was in
full service with no possibility for interruption.
Upon unearthing the existing 84-inch stub-out, suspicions
were confirmed that the dished head plug was external, not
internal. The contractor implemented a temporary support
system using nylon straps to support the stub-out piping
while the surrounding soil support was excavated.
Connecting to the external dished head plug would be
easier said than done, with the outer diameter of the existing
84-inch being different than the outer diameter of the new
84-inch connection piping. After grinding off the existing tape
coating, Main Lane Industries used a butt strap to connect a
new 84-inch spool piece to the existing 84-inch stub-out. Field
modifications to the butt strap were needed to make it work.
Special delivery
Good things come to those who wait. After a nine-month lead
time, the huge gate valve made its final journey from Alabama
to Texas in July 2020. The valve, approximately 22 feet long
and 4 feet wide, weighed a whopping 34.6 tons, the equivalent
of a brontosaurus, or three great woolly mammoths.
On a hot and sunny summer day, a small crowd of
engineers, managers and representatives patiently waited
as the valve was lifted from the 18-wheeler flatbed with
the crane and lowered into place. The bolted fasteners, 130
in total, took a day and a half for crews to complete.
Once the piping and valve were in place, the contractor
completed the concrete foundation and vault. The structure
itself was more than 400 cubic yards of concrete. For vault
cover and access, LAN designed a four-panel access door,
with access points that would permit the 84-inch gate valve
operator and bypass to operate without removing the panels.
Once complete, these vault panels were sealed with caulk and
covered in a shallow layer of soil and grass sod, so all that could
be seen from the ground surface was the air release valve cabinet.
Conclusion
" Design and construction of such a massive interconnection was a
big challenge to the project team. It required innovation, teamwork
and communication from every member of the team, " said Kevin
Tran, P.E., supervising engineer at Houston Public Works.
The interconnection was successfully completed with site
restoration in January 2021. Houston's legacy continues with
its groundbreaking water infrastructure expansion programs.
The city of Houston's drinking water system maintains a
" superior " rating, the highest rating for water quality issued
by the Texas Commission on Environmental Quality. *
CHRISTINE KIRBY, P.E. is a senior associate and senior project
manager at Lockwood, Andrews & Newnam, Inc. (LAN), a national planning,
engineering and program management firm. She can be reached at
chkirby@lan-inc.com. RAM CHAKRADHAR, P.E. is a project manager
at City of Houston Public Works, Capital Projects, Facilities Delivery
Line, Surface Water Transmission Program. He can be reached at ram.
chakradhar@houstontx.gov.
prevent this
DIVISION OF REEF INDUSTRIES, INC.
pipeline Protection
Highly Effective
underground warning tapes
Concrete is placed for vault walls. (Photo Credit: LAN)
800.231.6074 * ter ratape.com
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Underground Construction - August 2021

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