A team working on the Hampton Roads Sanitation District’s Shipport Treatment Plant Conversion and Transmission Program reached a milestone in May when it completed the installation of more than 5,700 feet of large-diameter pipe under the Newport News shipping channel in the James River in a continuous pipe. operation that lasted more than 24 hours.
The 42-inch-diameter DR11 HDPE pipe will be part of a wastewater main connecting from a new pumping station being built along the river in Newport News, Va., to the plant Sanitation District (HRSD) Nansemond treatment. in Suffolk, Virginia. To install it, the team used horizontal directional drilling.
The team initially planned a water-to-water directional drill of about 4,000 feet, but realized they could eliminate one of the water platforms by extending the drill, says Paul Longo, senior associate and senior project manager at Dewberry. the lead engineer of the submarine transmission pipeline installation.
“Extending it would add almost half a mile of drilling length and push the limits of the material, the drilling operations, the mud handling systems, really the limits of the trenchless installation industry for this particular pipeline with such a large diameter and being HDPE,” he says.
The team, which also includes contractor Garney Construction; Huxted Trenchless, who conducted the drill; Brierley Associates, who worked on the geotechnical and trenchless design; and Seaward Marine, which provided the piling and rig installation, determined what they would need to make the longer pipe work. The team conducted additional geotechnical investigations and spent seven days conducting a pilot drill to verify conditions under the river.
“This gave us confidence in the ability to carry out the execution and ultimately make it successful,” says Jordan Carrier, executive vice president of Garney’s Eastern Pipeline.
Although steel pipe would have had a higher safe tensile strength, the team had to use HDPE due to the corrosive marine environment. They found an HDPE pipe manufacturer in Texas, Performance Pipe, who was able to meet their specifications for ovality tolerances and the ability to handle external loads. The team also used a pipe pusher from German equipment manufacturer Prime Drilling that was custom designed for large diameter HDPE. Carrier says the lead time to get the pipe wrench was more than a year.
The team’s work platform in the river housed the pipe push and they placed the pipe through it before pulling it back to allow it to pass freely or with additional compression. Then they were able to use the pipe pusher to add compression to the back and relieve the tension from pulling, Longo says.
“We’re talking about 5,700 feet of pipe,” Longo says. “You can’t even see the end.”
Crews ran the pipe through the rig from a platform in the river. Photo courtesy of Garney ConstructionThe soft ground under the river posed a challenge, especially with the long-duration drilling. They dealt with this by installing the drill path deep, Longo says. The elevation of the bottom tangent of the drill was more than 170 feet below the surface of the water.
The team spent months building the pipe, fusing it and staging it before the start of the operation to put it in place on May 1. The actual stretching of the more than a kilometer long pipeline began that day and continued for 39 hours until evening. on May 2 in an operation that involved dozens of workers, according to Garney. Pulling had to be done in a continuous operation because of the difficulty of resuming after a shutdown with ground friction and the risk of something happening out of their control in the busy shipping channel, Carrier says.
“Once you start, you don’t stop,” he says.
The team will place 4.5-inch-thick concrete mats over the pipe to protect it from anchor shocks and other potential sources of damage.
“It’s such a critical asset that HRSD can’t afford any kind of impact on the pipeline after it’s installed,” says Carrier.
The pipepull operation took more than a day. Photo courtesy of Garney ConstructionThe next stage of the work will be the installation of another 3.5 miles of pipeline across the river using an open-cut marine installation. Longo says trenching, installing, ballasting and covering the pipe will take 12 to 18 months.
HRSD estimates the cost of installing underwater pipelines at $136 million. It is part of Boat Harbor’s larger treatment plant conversion and transmission program, which is being done as part of its Sustainable Water Initiative for Tomorrow (SWIFT), to eliminate sediment discharge from a treatment in Newport News, Virginia. on the James River.
The Boat Harbor treatment plant site is being converted into a pumping station to send wastewater to the treatment plant across the river in Suffolk at an estimated cost of $196.5 million, according to HRSD. Another 7,000 feet of pipe is being installed in the ground at an estimated cost of $38 million.
Garney has four of the five projects associated with the program. In addition to the submarine force main pipeline installation, the company is working on the onshore portion of the pipeline installation, the Nansemond Treatment Plant’s advanced nutrient reduction upgrades, and the installation of lations of the Sustainable Water Initiative for Tomorrow (SWIFT).
The entire project is scheduled to be completed by the end of 2026.
