Rapid Pipe Rehabilitation with Limited Community Impact

While working in Maryland’s Baltimore County, Ecotone LLC, an environmental construction management firm, discovered it needed to rehabilitate 96 linear feet of corrugated metal pipe. The challenge was, the twin 72-inch pipes passed under a county road that accessed an apartment community’s main offices and beneath the community’s swimming pool. The pipes had suffered extreme deterioration from prolonged exposure to constant running creek water. Small voids were now evident, creating pipe failure concerns.

The single point of access to the main office eliminated the traditional dig-and-replace method as a viable option due to the potential safety impact of limiting accessibility for fire and emergency medical services. Open cut was also ruled out because it could endanger children at an existing playground directly adjacent to the site. Unfortunately, this latter concern prohibited several other trenchless methods as well.

Solution

Pleasants Construction won the project, bid as a $250,000 cured-in-place-pipe (CIPP) lining job using the Alphaliner 1800H ultraviolet light-cured, glass-reinforced pipe (UV GRP) liner system. Two segments of 72-inch corrugated metal pipe (CMP) — each 48 feet long — needed to be lined.

Logistics challenges included the location of the creek ravine containing the pipes, which was between the roadway and a CSX railway track. The culvert area was protected by a fence and overgrown with weeds. This situation required some cut-in of a temporary work area for equipment and the liner crate as well as crew access. The crew also had to create an area to build their sandbag weir and to accommodate diversion for bypass pumping. Although a significant rain event occurred the afternoon and evening before the installation, the storm caused no issues or delays, thanks to proper site precautions by the crew.

The installer meticulously cleaned and inspected the pipes in preparation for the lining process. They spent the first day performing a televised line inspection and using their hydro-excavation truck to pressure-wash and clean out the pipes. The second day was devoted to clearing debris and preparing the pipe’s interior surface. During preparation, the crews were diligent in ensuring the safety of the general public and community, who were curious about the ongoing work.

The weight of the resin-impregnated liners required a 40-ton crane to lift the liner crates off the truck and assist in setting them down in the crews’ work area. The crews pulled the Alphaliner product into place and introduced air into the liner for expansion into the failing host pipe.

With less than 8% elongation, the Alphaliner glass-reinforced pipe product was the perfect solution for this project. Using the Reline America REE4000 curing unit, crews successfully cured the liner in place without any impact on the surrounding community or existing creek flows.

Each pipe required a full day for installation and curing. A second day allowed for quality control testing and site remediation. Throughout the process, the construction manager provided bypass pumping. Within 48 hours of crews arriving on site, the pipes were rehabilitated and returned to service without any trenches or open-cut excavation.

Results

With the installation of the Alphaliner 1800H liner, structural concerns — both present and future — have been eliminated. Due to the project’s success and limited community disruption, the local municipality has begun utilizing UV GRP lining on a number of problematic lines throughout the county, as well as for stormwater assets and failing outflow lines.