The 2016 Trenchless Technology Project of the Year for New Installation is an intricate and complex horizontal directional drilling (HDD) project that involves the installation of two parallel 32-in., 7,020-ft bores 60 ft below river bottom in an environmentally sensitive area in order to ultimately install underground electric lines. The project — known as the Indian River HDD Crossing — was part of a much larger endeavor to secure electrical infrastructure for some 4.8 million customers, ensuring reliable service in the face of severe weather. Installing electric lines underground is an application that more utilities and municipalities are turning to in order to keep service in tact during times of severe weather and other causes of outages. This project was accomplished through the ingenuity of the contractor and engineer through their thorough planning, engineering and implementation, as well pushing the envelope in utilizing Fusible PVC pipe (FPVCP) and HDPE pipe. RELATED: Canada Pipeline Project Turns to Trenchless The HDD work — which used the intersect method to construct the pilot hole — was part of a 13.65-mile long installation project by a large Southeast utility to upgrade its 230 kV underground transmission lines. A critical stretch of this alignment was the HDD section, which crossed a significantly-sized river. Mears Group was the contractor that successfully took on this impressive project, which simultaneously crossed and undergrounded the two circuits, utilizing two separate bores and two separate casings to house the required conduits for the high voltage power cables. Each FPVCP casing ultimately housed four 10-in. and two 3-in. HDPE conduits in a specially formulated thermal grout. “The project was called a Reliability Project,” says Mears Group project director and HDD industry veteran Ron Halderman. “The new lines give a secure way to move electricity between the plant and the mainline grid in case there were issues, such as weather, to ensure there is a reliable source of electricity. That’s what this project is for.” Halderman and FPVCP manufacturer Underground Solutions Inc., an Aegion Co., note this project resulted in significant advancements for the HDD industry. “These dual bores were the longest Fusible PVC installation that had ever been done. It was the longest installation of HDPE conduit in HDD crossings. And it was the longest HDD installation for power cables that had ever been done,” Halderman says, checking the records off his list. “We reached a new threshold for the electrical industry, pushing the envelope to a point that had never been achieved before. This was very challenging because we were in new technical territory, making this kind of project work. We also had to factor in the substantial logistical problems on the exit side of the crossing, having to pull the Fusible PVC casings and then later the HDPE bundled conduits, along a busy highway, across the water, then over mangroves to reach the exit points the HDD bores.” “The use of a non-metallic casing at lengths greater than a couple thousand feet provides the electric power transmission industry another key tool for projects,” says Underground Solutions vice president of engineering and technology Tom Marti. “In crowded urban areas there is not enough land or rights of way for overhead lines. Underground bury of the lines that inherently includes challenging HDD sections can be done, as demonstrated by this project.” The project required complex HDD equipment site setups to accommodate the two large rigs — a 1.3 million-lb Prime Drilling rig on the entry side and a 140,000-lb American Augers rig on the exit side — and support equipment, which included two American Augers 1000 Cleaning Series Mud Systems, as well as two sets of 7,020 ft of 32-in. Fusible PVC and 10-in. HDPE pipe (supplied by ISCO Industries). The FPVCP casing pipe (each casing weighed 385 tons) was fabricated and assembled northeast of the drill exit site along a busy highway. Each casing assembly navigated a 100-degree horizontal curve, floated across a creek and navigated trough an aerial insertion to the insertion pit. Once the HDD installations of the casings were completed, a unique thermal grout was used to fill each FPVC casing. Then open-ended cable conduit bundles were pulled through the grout for the entire length of each casing in order to lessen the pull loads due to buoyancy issues, and finally to accept the high voltage cables. The casings were installed over the winter of 2015/2016 and the conduits were installed in spring 2016. RELATED: Innovations Drive Industry Growth – New Installation There was minimal operational space on the exit side, due to the environmentally sensitive and protected mangroves in the area. Moving the equipment for the second, parallel bore just 50 ft away, was logistically infeasible. “There was no room to move the exit side rig. The rig had to sit where it was and we turned it on an angle of about 10 degrees, and then drilled out along the horizontal curve until it got 50 ft away from the first bore. Then we drilled straight across the river,” Halderman says. As for the prefabrication of the FPVCP casing, that proved to be a challenge, as well. The casing was sub-assembled in three lengths approximately 1 mile from the HDD entry point. To get to the top of the entry point, the casing was manipulated through a tight radius, 100-degree turn from a north-south alignment [along the highway] to an east-west alignment to cross the intercoastal waterway. Two intermediate fusions, using a McElroy 1648 Medium Force fusion machine, were done to join the three subsections into a single 7,020-ft length. An aerial transition needed to be made to raise the casing over the mangroves to the entry point. A vertical curve, supported by six hydraulic cranes with cradles, was used to position the casing for entry for the HDD install. A ballast line was installed and the pull head changed out. “Getting the casing to the entry point took much longer than the actual HDD pull-in,” Marti says, noting, the complexity of moving a 385-ton, 7020-ft long assembly a mile around a 100 degree corner to the drill exit point. To assure that the bend radius was held, Mears installed piling every 50 ft along a 2,160-ft transition and then anchored a 42-in. culvert to the piling, resulting in a continuous support throughout the turn.