Mears Group Inc. completed in April a 7,400-ft horizontal directionally drilled (HDD) bore in Jacksonville, Fla., a design-build project that allows a regional energy producer to expand its natural gas pipeline to serve new facilities.
To complete the project, Mears drilled a 7,400-ft pilot hole beneath the St. Johns River at a depth of 130 ft below the river bottom to install the 16-in. steel pipe. It is an essential link in a 50-mile pipeline that ends at the Jacksonville Electric Authority (JEA) Greenland Energy Center.
Though just 1.4 miles of the 50-mile pipeline, the section under the St. John’s River proved the most daunting in the planning stages. “This was the biggest obstacle to go from one side to the other,” said Mark Haney, director of engineering for TECO Peoples Gas, the company that owns the pipeline.
Haney said HDD was virtually the only option to install the pipeline through that area. “Other than HDD, there were no other good options,” he said.
But project officials said the timing of the project was also a major issue.
Haney said that the pipeline providing service to the power plant will be operational by Jan. 1, 2011. That means JEA was dependent on the pipeline being in place in time to move forward on the operation of the power plant. To help ensure a timely project, TECO hired Mears to complete a design-build project.
“If it is not built on time, you literally have a billion-dollar power plant there with no fuel,” said John Fluharty, project manager for J.R. Giese Operations, Mears’ sub-consultant that handled engineering duties.
Fluharty says design-build allowed Mears to drill a pilot hole months in advance to pulling product pipe to ensure the project was feasible.
“[TECO] wanted to know that early enough in the process so they would know if they needed to go another direction,” Fluharty said. “[TECO] wanted a true partnership put together so they could work out all the issues related to this special feasibility hole we did in advance.”
Design-build is relatively new to the HDD industry, Fluharty said.
Design-build offers a subtle but important difference from the typical procedure for HDD projects. In the typical process, a company, such as TECO, would hire an engineer to develop plans, procure a construction company to implement those plans and then construct the project — often called design-bid-build. Design-bid-build requires multiple contracts.
With design-build, however, a single company is hired to engineer and to build the project, all under a single contract.
Susan Hines of the Design-Build Institute of America says using design-bid-build can create contention between the engineer or designer of a project and the company that constructs the project. She said it creates a disconnect between the two parties that can often turn contentious because of concerns of liability and litigation. For instance, Hines said when the construction company finds changes need to be made to designs during construction, it takes paper work and dialogue for the changes to be approved and implemented.
“It slows things down a lot,” she said.
In the end, design-build projects help to improve two important aspects of any project: money and time.
Design-build projects cost at least 6 percent less than design-bid-build projects and are constructed 12 percent faster, according to the Design-Build Institute of America. At the same time, the institute reports that design-build projects earned the highest owner satisfaction than other project concepts.
“One of the main advantages of design-build is the fact that everyone on the design and construction job is on the same side,” Hines said. “They are all sharing in the risks and the rewards of a job well done.
“Owners save money, they save time,” she said.
Mears drilled the feasibility pilot hole for the project in November 2009. Product pipe was pulled in April 2010. Mears project superintendent Mike Maxwell said the crew drilled from both sides of the St. Johns River and intersected the two holes under the river — a waterway lined with stately homes and used mostly for recreational purposes.
A 330,000-lb rig was used for the pilot hole on one side of the river and a 140,000-lb rig was used to drill from the opposite side.
Mears used its 500,000-lb rig to perform the reaming and to pull the product pipe through the hole, Maxwell said. The crews reamed the bore to 24-in. diameter and then swabbed the hole before pulling the product pipe. The crew drilled through sandy silt before making it to clay for the drill’s running depth.
“It was fairly easy going. We were able to use a jetting bit all the way through,” Maxwell said.
Maxwell said the length of the drill combined with the unique aspects of the job, made it a satisfying accomplishment.
Stephen Tait is a freelance writer in Port Huron, Mich.