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EcoCast™ High-Strength Polymer Concrete Liner Provides
Cost-Saving Solution for Rehabilitating Corroded Culvert
Located in the heart of California’s industrial and commercial hub, the city of Vista is home to a master
planned 80-acre commercial/industrial community in the southeastern part of the city. A major artery
serving these properties is Business Park Drive. As part of the Drive’s construction in 1987, the city
installed a 15 ft. diameter corrugated aluminum multi-plate arch culvert that crosses under the Drive to
provide access along the City’s sewer easement for maintenance vehicles and trucks, and to serve as a
crossing for wildlife. Today, the culvert is also used as a tunnel by joggers and bicyclists.
Accelerating Corrosion Attack
In 2002, according to Greg Mayer, City Engineer, City of Vista/Buena
Sanitation District, City staff began observing corrosion of the culvert pipe
structure that progressed steadily over the years. Alarmed by the rate of
acceleration, the City sought recommendations from engineering
consultants to either remove or rehabilitate the structure.
Rehabilitation Requirements
The City decided against replacing the culvert, opting instead for
rehabilitation. Due to the oval shape of the pipe and its use as a roadway
underpass for both sewer and fire trucks, rehabilitation needed to follow the
same profile of the existing CMP. The primary design criterion was to
support the earthen embankment and any live vehicular loading. Another
requirement was that the exposed culvert material be non-flammable and
resistant to heat, as City staff had observed campfire remnants within the
culvert.
These design requirements eliminated some options such as High Density Polyethylene
spiral lining and epoxy lining systems. Consequently, concrete or steel rehabilitation systems were
recommended to meet the design criteria.
Environmental Concerns
To minimize impacting sensitive areas surrounding the project site (coastal sage scrub and
wetlands/riparian habitats), the City required that all work be performed inside the culvert and any required
staging areas be established in disturbed dirt areas that are located within 500 feet from both the upstream
and downstream openings of the culvert. In addition, the City determined that any rehabilitation solution
must be constructible with a minimal work area footprint and be able to utilize the existing access roads
into the bottom of the canyon.
Rehabilitation Solution
The City considered several rehabilitation alternatives using the existing pipe. Design proposals included
slip lining the pipe but that would have reduced the diameter of the pipe. It would also have impeded the
ability to drive trucks through the pipe. Another proposal was to use shotcrete but that had similar
limitations due to the thickness required to achieve the final design strengths.
Seeking an alternative that would not only rehabilitate and stabilize the pipe, but also support its
environmental concerns, the City chose a design/build solution from Inland Pipe Rehabilitation (IPR) of
Houston, TX based on qualifications and service offerings. The solution involved applying IPR’s
EcoCast™ high strength fiber reinforced polymer concrete liner directly to the host pipe in layers with no
specialized bonding application or engineered system required.
Developed by IPR and Milliken Infrastructure Solutions of Spartanburg, SC, EcoCast™ combines
advanced installation and application equipment with a custom formulated geopolymer called GeoSpray®
.
Unlike traditional cement mortars, the geopolymer is capable of bonding and building to great thicknesses.
Roadway Culvert
Installed in 1987, the 245 ft.
long corrugated aluminum
multi-plate arch culvert is 15’2”
tall and approximately 15 feet
in diameter. It extends beneath
Business Park Drive, just south
of Park Center Drive in Vista,
CA. It is comprised of
corrugated aluminum sheets
bolted together. The material
in the culvert liner is Kaiser
Aluminum Alloy 5052 with a
plate thickness of 0.150-inch.

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Product Specifications
Specifications included a thickness requirement of 2.5 inches, as well as microfiber and polymer additives
in the geopolymer to achieve a minimum 28-day compressive strength of 8,000 psi and 28-day flexural
strength of 1,300 psi as tested in accordance with ASTM C293.
How it Works
EcoCast™ is applied with a precision-controlled spray application apparatus, or is troweled on, depending
on the type of structure. “EcoCast is an extremely versatile system and was specifically developed for very
large diameter structures such as this one,” said Rob McCrae, IPR’s Chief Operating Officer. “For this
project, we determined the best method of application was to spray-apply the primary coating, then follow
up with troweling to create a smooth finish.”
Installation/Construction
One of the advantages of EcoCast™ continued McCrae is that “We can layer the material so our
crews can stop and start at any time, allowing the application of evenly applied product up to the required
thickness.” With a crew of five installers and one project manager, IPR completed the rehabilitation project
within the projected two-month time frame with no overtime or weekend work required. “The City was
impressed with the speed and expertise of the crew who viewed safety as a number one priority and fully
understood the project’s constraints,” added McCrae. In addition to installing the EcoCast™ liner, the
project construction included grading a new access road, installation of a SWPPP measure due to the
work being performed next to a stream, demolition of the existing asphalt roadway, and construction of a
new roadway slab.
Unforeseen Challenge
During the rehabilitation project, the IPR crew encountered movement in the pipe after removal of the
asphalt roadway. “The asphalt was not just a roadway for sewer trucks, it also locked the structure in
place,” said IPR’s General Manager, Schalk Opperman. “When we started to remove the asphalt we
realized that we would have to duplicate the roadway/slab function to eliminate movement in the pipe. The
challenge was to replace it with a structural slab that would be traffic rated and strong enough for large
sewer and fire trucks to pass through. It needed to be thick enough — and consist of enough rebar — to
withstand the anticipated loads of large trucks. The constraint was that we would have to stay within the
rehabilitation envelope. The difficulty was constructing a slab that could be no more than 5 inches thick.
Most conventional traffic-rated concreted slab is 9 inches thick, but that would have put us outside the
allowable envelope.”
The solution was to use EcoCast™ to construct the slab due to its high strength characteristics.
“We imported 5 inches of gravel, fixed #2 rebar and poured a 5-inch thick layer of geopolymer,” said
Opperman. “Regular concrete would have required a much thicker slab because of its lower compressive
strength. Using the high-strength EcoCast™ material, we were able to achieve the HS20 traffic loading
required and stay within the rehabilitation envelope.”
Conclusion
The rehabilitation project was completed both on time and within budget. Upon completion, several
measures were taken to verify the thickness of the EcoCast™ installation. First, IPR drilled set screws into
the crown of the CMP rib and measured the required 2.5 inches as per engineered design. Second, IPR
and the City agreed to have a testing laboratory conduct comprehensive testing of the materials to ensure
the design criteria were met. Twenty samples were tested and all were successful.
Commenting on the final project, Opperman said, “Not only was EcoCast™ the product of choice
when it comes to the circular rehabilitation it is known for, we now know it has the ability to cut down on
slab thickness when that is a construction constraint. With EcoCast™, the same structural requirement can
be achieved with a lot less material and with no loss in capacity. This is a big factor in storm water
rehabilitation.”
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