Underground Infrastructure - August 2023 - 38

REHABNEWS
First Aqueduct Water Pipeline Rehabilitated
with Geopolymer for SDCWA
When the San Diego County Water Authority (SDCWA) inspected its
First Aqueduct water conveyance system in Valley Center, engineers
identified that rehabilitation was required. Groundwater was infiltrating
three tunnels within the system and rehabilitation was required to
maintain the tunnels' structural integrity and extend their service life.
Michels Trenchless Inc. was chosen to develop design-build
solutions for the project. The organization partnered with Stantec for
engineering services and GeoTree Solutions joined the group to provide
rehabilitation materials for two out of three tunnels included in the
project scope. GeoTree's GeoSpray 61 geopolymer mortar was used to
rehabilitate portions of two 72-inch horseshoe-shaped tunnels, known
as Lilac Tunnel and Red Mountain Tunnel.
The third tunnel was rehabilitated using fiberglass-reinforced
polymer pipe and grout via sliplining. To carry out the required repairs,
the authority identified three 10-day shutdown periods, during which
204 hours of production work was possible. December 5 to 15, 2022;
January 23 to February 2, 2023; and February 27 to March 9, 2023.
A 500-foot section of the Lilac Tunnel displayed minor water
infiltration. A solution was developed to apply a 1.5-inch layer of
geopolymer to the entire section after cleaning, filling the haunches
with approximately 2 inches of GeoSpray 61.
A 3,100-foot section of the Red Mountain Tunnel also had moderate
infiltration and, again, a 1.5-inch layer of geopolymer was applied after
cleaning to mitigate the infiltration of groundwater. Haunches were
filled with approximately 2 inches of GeoSpray 61.
The Lilac Tunnel rehabilitation was completed during the first shutdown,
as well as the work to fully grout the Red Mountain Tunnel. Work on that
tunnel was performed from two temporary access portal locations.
The first half of the geopolymer application was completed during
the second shutdown and the second half was completed in the early
portions of the third shutdown. Following the geopolymer applications,
the Lilac and Red Mountain tunnel sections were completed and
released back to the Water Authority on schedule.
Spray materials
GeoSpray 61 was chosen for the project for a range of reasons. The
rehabilitation needed to meet NSF/ANSI/CAN-61 certification for
drinking water contact, a standard met by GeoSpray 61. Physical
properties of the material also played an important part, such as 1500
psi flexural strength (ASTM C78), fast-setting and curing, and chemistry
to self-bond without cold joints when multiple layers are applied.
GeoSpray has gone through a rigorous certification program through
the Water Research Centre (WRc) including the material and design
approach. GeoSpray 61 has proven application in deepwater heads,
meaning it can be pumped a long distance without setting. Therefore,
the temporary access points were sufficient to feed the workers inside
the pipe carrying out the application.
GeoSpray 61 was applied using Michels Trenchless' proprietary
centrifugal application devices specifically designed for the 72-inch
tunnel. For the Lilac tunnel alignment, GeoSpray 61 was pumped
approximately 750 feet to the application device and retracted at the
appropriate calculated speed. The total thickness was applied in two
passes, each of ¾ of an inch.
For the Red Mountain alignment, the material was mixed topside and
conveyed into specially designed diesel conveyance carts and delivered
to the application device for installation.
Two crews consisting of approximately 30 members took 26 days to
complete the project including preparation time.
" Trust between the customer, contractor, engineering firm and
material supplier is essential with all critical infrastructure projects, " said
Michels Trenchless President Matt Smith. " This project had a particularly
challenging timeline and conditions. As a result, we only had one chance
to get this right and provide safe, clean water to more than 3 million
people. Our experience and the ability to work with products and teams
we had confidence in allowed us to achieve the project's goals. "
GeoTree Solutions is a leading, global provider of highly engineered
solutions for repairing, rehabilitating, strengthening, and protecting
critical infrastructure, spanning the water and wastewater, oil and
gas, industrial, and civil sectors. The company is part of Critica
Infrastructure, which provides highly engineered and proven solutions
used to construct, maintain, strengthen, protect, and rehabilitate
energy transmission and distribution lines, high-consequence industrial
pipework, water pipelines, tanks, storm and sanitation systems, and
civil/structural assets. UI
FOR MORE INFORMATION
Critica Infrastructure, (281) 915-0752,
cs-nri.com/brands/geotree-solutions
38 AUGUST 2023 | UndergroundInfrastructure.com
http://www.cs-nri.com/brands/geotree-solutions http://www.UndergroundInfrastructure.com
Underground Infrastructure - August 2023

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