Trenchless culvert replacement typically calls for auger boring or pipe ramming, but full replacement isn’t always necessary. Cured-in-place point repair offers a permanent, alternative solution to culvert replacement with significantly better economy in some culvert remediation jobs.

Point repair is appropriate for round and oval pipe of a variety of materials, including clay, concrete, steel, cast iron, stone, corrugated metal and plastic. Defects such as deteriorated inverts and joint separation existing in otherwise sound storm and sanitary sewer mains, ventilation shafts or culverts can be excellent candidates for restoration using CIPP point repair.

Depending on composition, the service life of most culverts generally ranges from 50 to 100 years. Harsh site conditions, which might not have been present when the pipe was laid but developed over the course of time, can shorten culvert life expectancy and lead to premature failure. Usually the pipe must be completely replaced. On the other hand, culverts with isolated defects such as cracks, leaks, joint offsets and joint separation can be quickly restored to full service life expectancy using the cured-in-place point repair technique.

Permanent solutions

For the past two years, Hurk Underground Technologies has been using CIPP point repair to give its railway customers greater flexibility in their maintenance plans. Headquartered in Grinnell, Iowa, Hurk Underground is a culvert cleaning, restoration and subsurface drainage specialist. The company is a railway contractor of choice for culvert repair and replacement techniques that include augur boring, pipe jacking, pipe ramming, pipe bursting and pipe swallowing, as well as for large-diameter pipe renovation and repair with mechanical banding, pipe lining and, since 2014, CIPP point repair. These permanent culvert solutions prove invaluable to railway customers, since they have negligible effect on sensitive railroad substructures and don’t interrupt commercial rail traffic.

Company co-owner Doug Uitermarkt says most of the CIPP point repairs his crews have made are in the northern regions of Hurk Underground’s service area where railroad substructures are subject to seasonal frost heave. The cyclical ground movement can cause the individual sections of bell and spigot pipe to separate from each other in only a few years.

“They usually don’t ask us to fix small separations less than 4 inches, but that’s up to them and their maintenance schedules. However, separations over 4 inches allow significant infiltration opportunities. We’ll see where they are actually drawing down ballast from beneath the railroad ties.”

In addition, Uitermarkt says the robustness of a CIPP point repair means he can confidently extend his customer’s culverts. Whenever the width or the elevation of a roadway must be increased, the substructure typically needs to be widened. Often it requires widening the substructure beyond the length of the existing culvert.

A cured CIPP joint used to connect the extension is not only seamless, but in most cases is stronger and more corrosion resistant than the original pipe material. It ensures maximum flow capacity well beyond the expected service life of the existing pipe. 

Uitermarkt says a CIPP point repair offers three significant advantages over mechanical banding. The first lies in the smooth edges of a CIPP lining. The thin, tapered profile of the finished CIPP point repair presents no impediment to flow and may actually increase flow rate capacities. The second is longevity. CIPP point repairs have high long-term strength retention and perform with superior abrasion and corrosion resistance. Third, in cases of joint separation due to soil movement, the CIPP point repair effectively eliminates the joint. Culvert integrity is no longer vulnerable to frost heave at the point of repair. From then on, soil can glide along the pipe without moving the pipe with it.

Uitermarkt says sometimes customers notify Hurk Underground of a culvert in need of repair, and sometimes Hurk crews will discover a pipe’s defects while cleaning. “Whichever way it comes about,” Uitermarkt says, “we work together with the customer to assess whether it needs attention right now or not and, if so, we advise which techniques should be used. Then we determine together which methods are most appropriate in the given case.”

Bridging gaps

In its first year using the CIPP point repair system, Hurk Underground helped one of its major railway customers identify 15 culverts that could be saved without full pipe replacement or lining. Some had joints that separated due to frost heave, but others needed repair to eliminate infiltration at holes, offsets and misaligned pipes. Most joints with less than 4 inches of separation were determined not to be a serious concern. The customer instructed Hurk Underground to repair only joint separations greater than 4 inches. Separations less than 4 inches were considered on a case-by-case basis, and some of those were also repaired.

In one example, three of the five bell-and-spigot joints in a 50-foot-long, 34-inch-diameter culvert had greater than 4 inches of joint separation. “The other two joints in the pipe we agreed were not significant enough to require repair at this time. But one of the three we repaired had a 14-inch gap with substantial infiltration causing reduced flow from debris accumulation,” Uitermarkt says.

Access to the pipe was difficult due to steep inclines and wetlands on both sides of the rail bed, but the point repair equipment is small and easily transported. “Basically, if you can get to the pipe to clean it, you can repair it,” he says.

The crew made a ramp on one side for skid loader access and then cleaned the pipe to eliminate debris and loose material. Pipes did not have to be completely free of moisture, as the resin is moisture-tolerant and will work even underwater. Once the pipe was cleaned, other than the CIPP point repair system itself and a small gasoline-powered air compressor, little else was required.

The crew mixed the resin and applied it to the 6-foot-long liner, ensuring the felt-fiberglass composite was thoroughly saturated. They placed the bladder in its protective sleeve and wrapped the wet-out liner around the bladder. Then they inserted the prepared bladder into the pipe, positioning it at the point of repair. The crew used a 1/2-inch air hose for faster inflation, filling the bladder with the small compressor in a little over two minutes to the manufacturer’s recommendation of 11 psi. The bladder was held at 11 psi throughout the cure.

“Usually a cure for a 34-inch repair takes 1 1/2 to two hours. But it was unusually cold that morning, with temperatures ranging in the 20s throughout the day,” Uitermarkt says. “That’s not as cold as you might think because you have to remember that the temperature of the pipe was actually higher. The ground not only insulates the pipe from the outside air but tends to warm it through ground-source heat effect. But we allowed an extra 30 minutes anyway, for good measure.”

The crew deflated the bladder and inspected the repair before moving to the next joint. A crew of four was able to complete two joints in a single day’s work.

Uitermarkt says CIPP point repair restored the expected service life of the 15 culverts at one-third to one-fourth the cost of total pipe replacement or relining.

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Working the system

For the past two years, Hurk Underground Technologies has been using a CIPP point repair system from HammerHead Trenchless Equipment to give its railway customers greater flexibility in their maintenance plans.

The CIPP point repairs consist of a corrosion-resistant fiberglass composite lining using an odorless, styrene-free, VOC-free, ambient-cure silicate resin. Hurk Underground co-owner Doug Uitermarkt says each repair system comes with all of the consumable components his crews need to install the repair, including an inflatable bladder, protective bladder sleeve, and a disposable ground cloth to work upon. While Hurk Underground primarily works with corrugated steel, reinforced concrete, and bell-and-spigot culvert pipes in the 24- to 48-inch-diameter range, the CIPP system is compatible with all pipe materials and is available for pipe diameters from 3 to 48 inches.

Applications compatible for CIPP point repair include vehicular and railroad roadway culverts, cased ventilation shafts, and storm and wastewater drainage systems. Repairs maintain the culvert’s inside diameter to within 0.25 inches, and overlapping bands permit coverage of larger areas up to the full length of a culvert and can also be used to add pipe, extending the length of the run beyond the original length of the host pipe.

Brian Kenkel, HammerHead Trenchless business development manager and CIPP point repair consultant, says the CIPP point repair products are certified by NSF International to NSF/ANSI 14, NSF SE 10990, the Uniform Plumbing Code and the International Plumbing Code. Once cured, the high-strength resin and fiberglass matrix meets structural design standards set forth by ASTM F1216. “And our CIPP point repairs have both an H20 live load rating for use under highways and a Cooper 80 live load rating for use in rail beds — and that’s on their own, independent of the existing pipe.”