Tri County Water Authority of Independence, Mo.

Precarious Project Is No Problem

In September, the Tri County Water Authority of Independence, Mo., replaced an exposed transmission water line with restrained joint PVC pipe.

The water line, which distributes potable water to three counties, runs beneath a creek bed downstream of a private lake. Water from the creek gradually eroded the soil over the years to expose the pipe. To keep the water safely flowing, contractors had to overcome rocky conditions and a steep hillside that ultimately created a more than 30-ft change in elevation, or more than three stories, from entry to exit pit.  Additionally, there were space constraints due to a county road that runs alongside the creek.

Tri County Water Authority project

Brooks Directional Drilling LLC relied on a Ditch Witch JT3020 and a Vermeer D100x140 to complete the boring for the Tri County Water Authority project.

Choosing the Best Method

According to Tri County Water Authority general manager John Overstreet, the agency considered several options before deciding on Certa-Lok C905/RJ restrained-joint PVC pipe. At first, the team considered replacing the 14-in, water line using an open-trench approach. That idea was quickly dismissed due to the space constraint because of the county road, the extremely rocky soil and the existing pipe that ran through a steep hillside.

“As we looked at it, there was a tremendous amount of grading work that needed to be done to backfill around the pipe and provide appropriate protection for it. Therefore, we began to look at other alternatives to replace the water line,” Overstreet said.

Overstreet and his colleagues then evaluated installing steel casing and a carrier pipe. Coming downgrade, however, they knew they needed a deflection of about 5 degrees and might not be successful in bending the steel casing. That idea was dismissed.

The team also considered HDPE pipe. However, due to its elastic nature, the Tri County Water Authority was concerned that if something went wrong during pull through, the HDPE pipe might stretch, narrowing the already reduced inside clearance and impeding the insertion of necessary pipe spacers. Plus, getting a fusion machine to the pipe on unlevel ground and with a small easement, would pose a problem. That’s when the team decided that Certa-Lok C905/RJ restrained-joint PVC pipe installed via horizontal directional drilling (HDD) would be the right choice for this project.

The Tri County Water Authority had previously used Certa-Lok Yelomine piping systems for temporary water bypass lines that were above ground. They were familiar with Certa-Lok’s simple, fast installation and strength. Certa-Lok C905/RJ uses precision-machined grooves, high-strength flexible splines and watertight O-rings for a fully circumferential restrained joint that locks the pipes together, while also allowing for immediate serviceability of its joint. Certa-Lok pipe can be easily assembled during pullback, making it an ideal solution for projects with space constraints.

Tri County Water Authority

After exploring several options, the Tri County Water Authority decided to use Certa-Lok C905/RJ restrained-joint PVC pipe.

Further, the more rigid PVC pipe enabled the water agency to use a smaller diameter pipe for the casing and carrier pipe, compared to that needed with an HDPE solution. The cartridge style joint allowed the water authority to eliminate the risk of having the pipe split from end to end in these aggressive soil and boring conditions.

With this understanding, the agency sought and received approval from the county to proceed with installing Certa-Lok pipe. This project marked the first time the Tri County Water Authority used cartridge-loaded restrained-joint PVC pipe for a permanent water infrastructure project.
“We thought this application would be very successful and a reasonable approach to water line replacement,” Overstreet said.

And it was.

Getting the Job Done

J & N Utilities, a company that provides maintenance for 10 water districts around metro Kansas City, Mo., and water main and sewer installations throughout the state, was awarded the pipe installation. Brooks Directional Drilling LLC of Burden, Kan., a firm that operates in all types of underground utility construction and specializes in directional drilling, was tapped for the drilling.

John Crawford, co-owner of J & N Utilities, said the drilling crew had to run the new line 22 ft deep into the ground, underneath the existing line and through all rock.

In addition, the creek ran alongside a county road giving the crew approximately 80 ft in which to place the equipment and assemble pipe, making Certa-Lok’s easy-to-assemble restrained joints critical to getting the job done right. The road remained open and the water continued through the existing line throughout the process.

Brooks Directional Drilling had a three-person crew use a Ditch Witch JT3020 directional drill with a 148-hp turbocharged diesel engine to create the 4-in. pilot hole. A new Vermeer D100x140 horizontal directional drill powered the rest of the project, along with 12-, 18-, 30- and 40-in. Straightline hole openers to break through the solid rock.

“We had to bore under a creek, at a county road and up a steep bluff to replace the exposed section of the water line. This required steering close to maximum steer rate for the pipe because of the short distance we had to accomplish it in and through solid rock,” said David Brooks, owner of Brooks Directional Drilling.

“It was an interesting bore. Like a lot of projects we get, it was a really big pipe to put into a small area. I intended to use a machine much larger than the Vermeer D100-140 because of the size of the hole and the rock, but a larger machine wouldn’t fit in the 20-ft wide easement between the road and the creek,” he said.

Though the work was slightly slower due to the smaller machine, Brooks said it allowed his crew to prevent break off of tools and rock. “It went smoothly,” said Brooks.

Once the reaming was complete, four workers with J & N Utilities assembled 320 ft of 24-in. C905/RJ DR 25 Certa-Lok casing and then helped pull 320 ft of 16-in. C905/RJ DR18 through the casing.

Certa-Lok was a good choice because the extra deflection at each coupled joint allowed the system flexibility required by the project’s natural elevation changes. “We had 32 ft of elevation change within 300 ft, which is over three stories. Ductal iron would not have made that transition. This pipe is much more flexible,” said Crawford.

J & N Utilities excavated earth to marry the new waterline to the existing one and used stainless steel joiners to tie the new into the old.
“The ease and durability of Certa-Lok pipe makes a difference during installations. It’s a pipe that’s easy to assemble so you can keep up while pulling pipe, even if you don’t have much room,” Crawford said.

The project may have been steep and rocky, but the process of installing the PVC pipe was anything but.
Chris Aldred is marketing communications manager with North American Specialty Products.
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