A railway in Vermont, US, has undergone an upgrade using a two-pass pipe-ramming and guided boring system.
Although it’s officially listed as only the ninth costliest hurricane to make landfall in the US to date, in 2011 Hurricane Irene caused at least 49 deaths and widespread destruction along a path from first landfall in the Caribbean spanning along the US eastern coast and well into Canada. By 29 August, Irene had made its way as far north and inland as Vermont.
The White River Railway Bridge, located in Vermont, was victim to the storm, with one granite pier sinking more than 1.8 m and threatening the total collapse of the bridge. Track washouts west of White River Junction completely shut down Amtrak’s high speed Vermonter rail service from 29 August to 1 October 2011.
While rail service has long since been restored, seven years after the hurricane the Vermont Agency of Transportation (V-Trans) continues to bolster railway infrastructure against future severe weather events of Irene’s calibre or greater.
Improving the system
In 2018, two V-Trans rail system improvement projects, funded by the Federal Emergency Management Agency, focused on ground stabilisation and drainage upgrades near Ferrisburgh and New Haven. The agency subsequently contracted Engineers Construction (ECI) to perform the scope of work for the projects.
Founded in 1965, the multi-division, family-owned contractor specialises in civil and full-service railroad construction, concrete construction, asphalt paving and trenchless pipe installation, and is an industry leader in steel casing installation.
ECI’s ability to seamlessly coordinate deployment and integrated task performance of its five divisions – comprising a fleet of more than 500 pieces of equipment and 175 dedicated personnel – assures its customers of highest quality work at greatest value in complex and highly technical projects.
All work on these two contracts was performed by ECI teams, with tasks ranging from heavy civil construction to sheet piling, earth anchoring and extensive erosion prevention and sediment control. The work included the installation of a new 30 m long culvert in New Haven and two replacement culverts – one 14.9 m and the other 15.2 m long – to upgrade flow capability near Ferrisburgh.
Each culvert required a two-pass installation system, installing 72 inch (1,829 mm) casings to receive an Ultra-Flo Smooth Interior Culvert carrier pipe varying by culvert in diameters of 42, 48 and 52 inches (1,066, 1,220 and 1,321 mm).
ECI Senior Project Manager Tom Loyer, who is also head of the company’s trenchless division, says open cut techniques were out of the question for these projects.
“Our rail and excavation crews could certainly do it but not between the scheduled trains,” he says.
“The busy line had to be kept running. This region has severely limited rerouting options.”
Mr Loyer preferred the auger boring method for the railway casing installations to meet the projects’ typically tight tolerances for grade and azimuth. While the New Haven site gave the crew ample space for an auger boring setup, site restrictions in Ferrisburgh were complicated by a shared boundary with environmentally protected wetlands.
Elevation wasn’t a problem here, as the shallower culverts were just under 1 m below the toe of the shoulder ballast, but the allowable worksite dimensions were too tight for an auger boring machine or construction of a backing wall. The site restrictions did allow for 12.2 m working pits, adequate space to operate a medium-sized horizontal directional drilling (HDD) machine and a pipe ramming tool setup.
“Combination pipe ramming and a guided boring method was an easy call on this job. We’re weren’t crowded then at all,” says Mr Loyer.
Other ECI divisions worked on sheet piling at the two sites and on grouting up the existing 100-year-old stone box culverts at Ferrisburgh. ECI’s trenchless crew began with the Ferrisburgh project. One pipe path was adjusted prior to installation operations to accommodate a ledge discovered during ECI’s preconstruction exploratory probing.
The ECI equipment fleet represents all major manufacturers in the market. In 2012, the company purchased its largest hammer, the HammerHead 24 inch (610 mm) ramming tool used for this job.
Mr Loyer’s personal experience with HammerHead equipment and support goes back more than 28 years. He and his brother, who has since passed away, founded Trenchless Technologies of New England, which he says was one of the first companies in the country to offer pipe ramming.
The team used one of ECI’s mid-sized Ditch Witch HDD machines to establish the grade and azimuth with 5 inch (127 mm) pipe. Once through the ground’s heavy clay conditions, a 24 inch (610 mm) Akkerman guided boring machine (GBM) weld-on reaming head was adapted for use centralising ramming operations on the pipe.
The pipe then guided ramming operations as the they installed the 24 inch diameter, 0.5 inch (13 mm) wall steel pipe casing into the bore using a small ramming tool. The casing served as the final ‘pilot pipe’ to guide ramming of the 72 inch (1,829 mm) grout-ported, 25 mm wall carbon steel casing.
“A 5 inch pipe, of course, won’t stand up to ramming operations on a 72 inch casing,” says Mr Loyer.
“Since these were relatively short runs in conducive soil, we only needed to step up to 24 inch pipe. In longer runs and tougher soils with similar, sensitive grade requirements, we might go from 5 to 24, and then step up again to 36 or even 42 inch pipe to drive a 72 inch casing.
“It all depends on the requirements and ground conditions of the job.”
ECI used a second Akkerman GBM weld-on reaming head to guide the 72 inch casing on the 24 inch pipe. The reaming head’s spoke-like blades allowed spoil to pass through as the casing progressed while ensuring it stayed centred on the bore path.
Two 755 L/s Caterpillar compressors supplied power to the HammerHead ramming tool. Each 6.1 m length of casing took a day to drive.
Adding a section to the installation required two certified ECI welders and a full shift to make the joint. Then, to clean out the pipe, the team used a 64 inch auger tool and skid steers.
“That basically got the pipe so clean, we just handed out shovels and a hose to manually wash out the little that was left,” says Mr Loyer.
The project plans initially called for contact grouting of the 72 inch casing. When V-Trans came to inspect the installation, it found heavy clay was densely packed around the pipe with zero voids detected at the ports. Contract grouting requirements were waived.
The crew installed cross-members within the pipe to support the polymer-coated carrier prior to performing the project’s requirement for annular grouted fill. ECI installed precast concrete headwalls and wingwalls, incidentally obscuring the culverts’ robust two-pass engineering.
“From the outside you can’t see all that fine work,” says Mr Loyer.
Fit for the future
With the works completed, the culverts have been strengthened for the decades to come; the next Irene to come along will not reveal their inner workings. The carrier within the two-pass system has a rated service life of at least 100 years.
Total project time – including culvert installations – took about six months, start to finish. ECI completed the two contracts within specification, on schedule and within budget, never disrupting scheduled railway traffic.
This article was featured in the Spring 2019 edition of Trenchless International. To view the magazine on your PC, Mac, tablet, or mobile device, click here.
For more information visit the HammerHead website.
If you have a project you would like featured in Trenchless International contact Assistant Editor Chloe Jenkins at email@example.com