In 2016, a public works crew in East Goshen Township, Pa., discovered that the bottom of a large (80 in. x 120 in. x 30 ft.) oval corrugated metal pipe culvert, running beneath Forest Lane, had rusted out.
Though a small road, Forest Lane is a significant connector between three main suburban Philadelphia traffic routes. It carries local traffic, including school buses, and no one wanted to see it closed for a traditional dig-and-replace job.
The structure had surpassed its service life, and fixing it was of immediate importance, since leaving it missing sections of its invert could cause erosion of surrounding soils. This could weaken the road’s compaction and, in an extreme rainfall event, even form sinkholes.
Township Manager Rick Smith was familiar with the culvert. In 1972, he had been on the road crew that had replaced it after during extreme rains from the remnants of Hurricane Agnes had washed it out. Now he had to decide how to replace it again. He and the township’s Director of Public Works, Mark Miller, visited the site to understand the exact nature of the pipe’s deterioration.
Trenchless It Is.
“Except for the bottom center section of the culvert, the rest was in excellent shape,” Smith recalls. “Replacing it in its entirety seemed to be overkill.”
There was also the matter that an open cut, dig-and-replace solution would be subject to stringent, environmentally sensitive permitting, that would require a complete culvert re-design. And everyone was eager to avoid an 8-week road closure and detour—and $175,000 price tag—estimated for such a project. Smith and Miller agreed that a trenchless solution was in order.
“We had previously used various types of (structural) coatings on sewer manholes and pipes with good results,” Smith says. “Our goal was to install a structural coating that essentially took the place of the metal culvert. So we had the engineer write what was considered an open spec.”
Design engineer Nate Cline of Pennoni Associates, the township’s consulting engineering firm, wrote that project specification, indicating a trenchless lining solution but leaving open what type of solution was acceptable. The township had worked with two contractors in previous lining jobs—one a steam-cured CIPP solution, the other a spray-applied liner—both of which had performed well.
Both companies were among the bidders on the Forest Lane project, for which the following solutions were ultimately considered:
- Inversion CIPP (felt liner)
- CIPP (fiberglass liner)
- Spray-applied epoxy
- Spray-applied polyurethane
All these methods were approved, as long as materials had verified, third-party testing on physical strength, and the manufacturer and contractor had extensive experience with similar projects. A final requirement was the ability to provide an engineered design thickness calculation for any solution.
Price and Performance, Pronto!
Abel Recon of Mountville, Pa., came in with the lowest bid of $66,000, nearly a third of what had been estimated for traditional dig-and-replace. This included bypass pumping to temporarily relocate active stream flow, and the installation of 600 mils of Sprayroq’s Spraywall structural polyurethane product.
Price was paramount, but performance value ran an immediate second in importance. Abel had demonstrated SprayWall’s performance in an earlier project, so Smith had confidence in it.
However, prior to bid, Pennoni required Sprayroq’s engineer, Chip Johnson, to provide appropriate design thickness calculations that would prove SprayWall was the best rehabilitative solution for the elliptical-shaped structure. Matt McAloon from Pennoni was present at the installation to ensure proper application and provide on-site inspection.
Groundwater pressure forcing soil through the missing pipe sections was eliminated with a cement waterstop mix, profiled to the host structure. With the active stream flow, continual bypass pumping was required. SprayWall’s immediate cure allowed for a cofferdam and through-structure bypass, putting the hose directly through the host pipe being lined.
Immediate Relief, Long-term Results
East Goshen was pleased with the single-day setup and installation, which required only the placement of traffic cones, rather than road closures and detours. SprayWall’s enabling of simplified environmental permitting and engineering provided massive cost savings, while its third-party-verified performance gave Smith and the township confidence that the expenditure was a long-term investment.
Perhaps most impressive is the project summary from an attendee from PennDOT’s Bureau of Maintenance and Operations, who witnessed the project as a SprayWall product demonstration:
“The verified engineered solution, utilizing a designed thickness in addition to the inherent field quality control monitoring, will allow this material to be a viable option for our Department of Transportation, as we continue to explore available technologies to better serve our public.”
Abel and Sprayroq both look forward to the day when Sprayroq products make the permanent list of approved PennDOT options. For now, it’s enough that Rick Smith and East Goshen Township can rely on them for continued performance in local municipal projects.