By Bob Wothe, Michels Corporation, and Randy Traylor, SCANA Corporation
What a difference six years makes.
In 2004, Michels Directional Crossings set a horizontal directional drilling (HDD) industry record for its completion of two parallel 7,080-foot-long, 8-inch diameter steel high voltage transmission lines beneath the Cooper River in Charleston, SC.
At the time, drilling and installing pipe at such a distance was considered almost inconceivable and a near-marvel of engineering.
Fast forward to 2010.
Fifteen miles upriver of the previous crossing, Mother Nature was winning a battle against a natural gas pipeline that crossed beneath the Cooper River. The pipeline, owned by Carolina Gas Transmission (CGT), a SCANA company, was installed in 1970 and served as the sole natural gas supply line for a number of coastal towns and direct industrial customers. The crossing was in a bend in the river that was eroding along the western bank and continually removing cover over a section of the pipeline. Despite CGT’s considerable efforts to stabilize the bank, something needed to be done.
“Nothing we do as a company is more important than providing safe and reliable transportation service,” CGT President Paul Fant said. “We take this responsibility very seriously. Our customers have consistently rated the reliability of our firm’s transportation service as being among the leaders in the industry. ”
Since continued erosion of the riverbank was inevitable and public safety and system reliability was of the utmost concern, CGT decided that the best course of action was to replace the pipeline across the entire riverbed. The new pipeline was to be located 40-feet beneath the river bottom and new mainline valves were to be installed on either side of the river to facilitate in-line inspections.
After performing engineering feasibility studies, obtaining the necessary permits and developing engineering specifications for the project, CGT issued a Request for Proposal (RFP) for the project. The RFP set forth two possible approaches.
The first option was for two directional drills to be completed, with a conventional open-cut trench to tie the drills together in the Cooper River tidal marsh area, which is a designated wetland. Although this open-cut and tie-in installation method would straighten and reduce the length of the drills, it would be time consuming and environmentally intrusive: the use of conventional construction techniques in the tidal marsh would have required the stabilization of the right-of-way with several layers of matting. The tidal marsh area would have required as much as 1,000 feet of matting from the west side, and high ground water would also have been an issue while conducting open-cut operations.
There was, however, another option: a single, lengthy 9,931-foot drill, the likes of which had never been done before.
This option wasn’t without its own unique challenges due to the presence of overhead electric transmission lines and power poles. And a nearly 10,000-foot drill with a slight bend in the middle wasn’t likely to be a walk in the park, either.
Because Michels had the technical expertise and past experience drilling beneath the Cooper River bed, CGT opted for the single drill option to avoid the myriad of environmental and logistical issues involved with the two-drill approach.
“In addition to the operational challenges of the open-cut portion, there were safety concerns associated with sloughing in the trench,” said Gray Lewis, vice president for Patterson & Wilder, a sub-contractor to Michels. “Working with CGT and Michels to perform one drill was a great solution that kept us from putting our workers in harm’s way altogether.”
The last Cooper River drill in 2004 gave Michels a base point to start from as they began to work on this innovative, record-breaking drill using the latest pilot-hole intersect technology.
Since their first drill under the Cooper River, Michels has continued upgrading its equipment fleet, tooling, methodology and steer technology, all of which made a much longer crossing possible. Still, drills of nearly two miles are far from commonplace because of the need for favorable conditions at every step along the way.
To plan and execute this particular project, Michels utilized the support staff of CGT and Patterson & Wilder throughout. This team worked together to push the envelope of HDD technology and conquer yet another nearly unthinkable distance.
The dramatic skew to the pipe pullback alignment meant that the 16-inch steel pipe had to be carefully snaked around many obstacles and safely pulled along the right-of-way for 20 hours, which included a four-hour mid-weld.
Michels’ Assistant Operations Manager, Tom Breunig, mastered the art of understatement when assessing the project.
“This was not an everyday job,” he said. “There were quite a few challenges that we had to stay on top of every single day. In addition to the normal contractual requirements, the U.S. Army Corps of Engineers had requirements, and we had different rules to follow on each side of the river because of being inside-plant with two different companies. Pre-planning with the project team and CGT worked to maximize safety while minimizing the challenges.”
On a complicated project such as this one, anything less could have led to disaster. As HDD projects have become more complex, the number of difficulties and challenges encountered on any one job has multiplied exponentially. The ability of Michels to work closely with CGT and Patterson & Wilder was crucial for the success of the installation.
“The length and environmental conditions were a huge challenge in and of themselves,” CGT Project Manager Barry Mills said. “Throw in the number of folks from different companies working together and you can see how the challenges become even greater. Fortunately, the teamwork and dedication of everyone came through with flying colors.”
Larry Collins and Randy (Devy) Traylor rounded out the oversight team from CGT, fulfilling the roles of on-site inspector and engineering manager, respectively.
For Michels, Breunig led a team made up of Jim McGovern, Larry Shilman, Wendell Long and Robert Spennati who all worked together as project managers on this complex job, and Paul Krings, Marcus Carratt, Bryan Ketter and Dan Reynolds were the drill superintendents.
Finally, in addition to Lewis, the Patterson & Wilder team included Vice President of Field Operations Cathy Cavender, Project Manager Ed Kosarek and Project Superintendent Danny Burden.
Together, this experienced and knowledgeable team completed one of the most impressive drills ever attempted.
“The successful completion of this complex project is just another example of CGT’s excellent track record of meeting the needs of its customers and other stakeholders,” Fant said. “Michels and Patterson & Wilder teamed with our group to move this project from drawing board to flowing gas while meeting scheduling and financial targets.”