Frontier Pipeline Completes Record Setting Rock Drills

December 2008 Vol. 63 No. 12

Frontier Pipeline LLC, based in Somerset, WI, with engineering/administrative offices in Duluth, MN, recently completed a successful project consisting of two parallel crossings for the installation of 48-inch HDPE pipelines under New Haven Harbor in New Haven, CT.

The two utility replacement crossings were completed for the Connecticut Department of Transportation (CTDOT) as part of the replacement and relocation of the Pearl Harbor Memorial “Q” Bridge.

The Advanced Sanitary Sewer Relocation project was necessary to replace an existing sanitary sewer force main that infringed on the proposed location for the new bridge. Frontier teamed with The Middlesex Corporation (TMC) for the project, with TMC providing marine support, product line fabrication/handling, and shoreline tie-in work. The project was awarded in early 2008 and drilling began in April 2008. The first product line was installed in early July 2008 and the final pipe pull back occurred in October 2008.

One of the biggest challenges facing the HDD installation was the continuous, nearly 45 degree turn in the horizontal alignment for both crossings over a length of approximately 1,900 feet in solid rock. This constant horizontal curve, creating compound curves when combined with vertical bends in and out of the crossing, tested the limits of the pilot hole surveyor and created new limits on what can be done using maxi-rig HDD.

“To my knowledge, a crossing with nearly 45 degrees of turning over a 1,900 foot length creating a 60-inch borehole through rock has never been attempted,” said Frontier vice president – HDD operations Dimitrios (Jim) Lagios. “This should be considered a record drill and everyone involved should be proud of a truly remarkable HDD installation.”

The project specifications contained tight regulations for inadvertent drilling fluid returns to the harbor bottom. Any release was believed to pose an adverse impact on the shellfish population native to the harbor. A patient approach to the drilling and reaming processes was necessary due to the soft soils on the western shore of the harbor and the undulations in the rock stratum. Extensive engineering controls, close monitoring and containment/clean-up plans were required in order to complete the crossings.