Underground Construction - May 2022 - 34

Manhole Rehab Project
to mobilize its team to get the project underway in August 2021.
The scope of work for IIS was a comprehensive rehab of
the seven-manhole chimney structures. At an average depth of
10 to 11 feet, the project was comprised of 80 vertical feet of
manhole risers, with a five-foot circumference of each structure.
With the proximity of the city of Eagle to the Boise River, and
the corresponding high-groundwater table, four of the seven
risers were experiencing infiltration and inflow; the team used a
hydrophobic pressure grout to address this issue.
The next step was some build back work on all the risers.
Integrity chose a high-early-strength patching material to fill
any voids in the concrete. As part of the surface prep, the contractor
also cut a keyway at the top of the chimneys, below the
grade rings, and a termination key at the spring line - versus
doing a monolithic down to the flow line - using a grinder to
" notch " the concrete.
This would help ensure a good solid termination point at
the edge of the coatings solution, and reduce the possibility
of undercutting, corrosion, disbondment or peeling of the
coating. Once the build back and keyways were completed,
the final step in preparing the surface was pressure washing all
seven of the risers, with a 5,000-psi rotary tip.
When considering a coatings solution for a manhole rehab
project, one option is polyurethane. But in this type of environment,
it would be difficult, time-consuming and expensive
to dry the concrete enough for it to take a typical polyurethane
coating. There was also too-much residual moisture
in the substrate to apply the polyurethane without extensive
surface prep.
As a result, an ultra-high-build epoxy coating was chosen -
Raven 405 from PPG Raven Lining Systems. The 100-percent
solids, zero-volatile, organic-compounds, chemically resistant
epoxy was an ideal solution for the manhole structures. It
could be applied on a saturated surface-dry (SSD) substrate,
saving a significant amount of time.
Raven 405 epoxy was applied direct-to-host, without a
primer, at 150-mil dry-film thickness (DFT). The pressure
washing done beforehand created the required surface profile
for the epoxy to both chemically and mechanically adhere to
the concrete risers.
In some rehab applications, an epoxy coating may seem an
excessive, expensive, and premium solution that isn't needed.
But with an environment with such high exposure to extreme
levels of H₂S, the epoxy was critical to providing a long, useful
life for the manhole risers - " as good as new, " for most any
sanitary sewer infrastructure application.
48 hours
Integrity Inspection Solutions works on the manhole coatings project in
Eagle, Idaho.
Once the film was dry (approximately four to five hours),
a final step was a comprehensive holiday test in the seven
chimneys, following ASTM and NACE industry standards.
The tests, using specialized, high-voltage equipment, ensured
there were no inconsistencies or imperfections in the 150-mil
DFT surface of the epoxy coating, such as discontinuities, pinholes,
holidays and voids.
Holiday tests are particularly important when applying
anti-corrosive coatings, as undetected holidays leave the underlying
substrate (concrete, masonry, metal) susceptible to
corrosion at those locations.
From start to finish, the IIS team took 48 hours to get the
job done. It was a quick and efficient project, made possible
by the knowledge and expertise of the team, but also by the
time-saving features of the 405 epoxy. With the ability to apply
the coating on an SSD substrate, and the brief window
from time of application to holiday tests, it proved an effective
solution as part of a long-term, ongoing maintenance plan for
any sanitary sewer district. *
ABOUT THE AUTHOR: Randy Gonzalez is the West Region Technical
Manager for PPG PMC Raven Lining Systems. He can be reached at
760-685-7784, or at gonzalezr@ravenlining.com.
FOR MORE INFORMATION:
Manhole after being coated.
34 MAY 2022 | UCONonline.com
Integrity Inspection Solutions, (208) 442-4470, iispipeline.com
Raven Lining Systems, (800) 321-0906, ravenlining.com
http://www.iispipeline.com http://www.ravenlining.com http://www.UCONonline.com
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