The team originally planned for a water-to-water directional drill of about 4,000 ft, 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 for the underwater transmission pipe installation. 

“Extending it would add almost a half-mile of drill length and would push the limits of the material, the drilling operations, the mud handling systems—really the limits of the trenchless installation industry for this particular pipe at such large diameter and being HDPE,” he says.

The team—which also includes contractor Garney Construction; Huxted Trenchless, which performed the drill; Brierley Associates, which worked on the geotechnical and trenchless design; and Seaward Marine, which provided pile and platform installation—determined what they would need to make the longer pipepull work. The team performed supplemental geotechnical investigations and spent seven days conducting a pilot drill to verify conditions under the river. 

“That gave us confidence in the ability to actually go through with the execution and make it ultimately successful,” says Jordan Carrier, executive vice president of pipe east at Garney.

While steel pipe would have had a higher safe allowable pull force, the team needed to use HDPE due to the corrosive marine environment. They found a HDPE pipe manufacturer in Texas, Performance Pipe, that was able to meet their specifications for ovality tolerances and ability to handle external loads. The team also used a pipe pusher from German-based equipment manufacturer Prime Drilling that was custom-designed for large diameter HDPE. The lead time on sourcing the pipe pusher was upwards of a year, Carrier says.

The team’s work platform on the river housed the pipe pusher, and they positioned the pipe through it prior to pull back to allow it to pass through freely or with additional compression. They were then able to use the pipe pusher to add compression to the back and relieve the tension from pulling, Longo says. 

“We’re talking 5,700 ft of pipe,” Longo says. “You can’t even see the end of it.”

Crews threaded the pipe through equipment from a platform on the river. Photo courtesy Garney Construction

The soft soil under the river provided a challenge, particularly with the long length drilling. They dealt with it by installing the drill path deep, Longo says. The elevation of the bottom tangent of the drill was more than 170 ft below the water surface. 

The team spent months constructing the pipeline, fusing it and staging it before the start of the operation to pull it into place on May 1. The actual pull of the mile-plus-long pipe started that day and continued for 39 hours until the evening of May 2 in an operation involving dozens of workers, according to Garney. The pull needed to be done in one continuous operation because of the difficulty of resuming after a stop with ground friction, and because of 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-in.-thick concrete mats over the pipe to protect it against anchor strikes and other potential sources of damage.

“It’s such a critical asset that HRSD can’t afford any sort of impact to the pipeline after it’s installed,” Carrier says.

The pipepull operation lasted more than a day. Photo courtesy Garney Construction

The next stage of work will be installing another 3.5 miles of pipe across the river using marine open cut installation. Longo says trenching, installing, ballasting and covering the pipe will take between 12 and 18 months. 

HRSD estimates the cost of the underwater pipe installation at $136 million. It is part of the larger Boat Harbor Treatment Plant Conversion and Transmission program, which is being done as part of its Sustainable Water Initiative for Tomorrow (SWIFT) initiative, to eliminate the discharge of sediment from a treatment plant in Newport News, Va., into the James River.

The Boat Harbor Treatment Plant site is being converted into a pump 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 ft of pipeline is being installed on land at an estimated cost of $38 million. 

Garney has four of the five projects associated with the program. Besides the underwater force main pipe installation, the firm is working on the land-based portion of pipe installation, Nansemond Treatment Plant advanced nutrient reduction improvements and Sustainable Water Initiative for Tomorrow (SWIFT) facilities.

The full project is scheduled for completion in summer 2025.