Trenchless technologies for infrastructure renewal

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    Many regions of the United States are facing a painful and seemingly inestimable task of keeping up with the need to restore their aging and increasingly inadequate pipeline infrastructures, particularly when it comes to meeting present and future needs of water, wastewater, and natural gas pipeline systems. The Mid-Atlantic region is a microcosm of a nationwide need to replace and expand all of these infrastructures. Even those states that may profit greatly from tapping Marcellus shale gas reserves will face the need to install a safe and efficient distribution pipeline system.

    One of the keys to replacing and expanding the pipeline infrastructure in an efficient, cost-effective manner will be horizontal directional drilling, auger boring, or pipe jacking. “This capability not only saves time and money, but can also save on disrupting the environment and exposure to potential hazards,” said Vince Rice, president and CEO of Aaron Enterprises in York, Pa. According to Rice, advanced horizontal “trenchless technology” can allow pipeline construction at a very fast pace.

    “There is a need for thousands of miles of pipeline to replace or expand the water, wastewater, and natural gas infrastructures in Pennsylvania alone,” said Brian Funkhouser, P.E., president and CEO of full-service architectural and engineering firm Buchart Horn Inc., also in York, Pa. The firm provides services in the transportation, water and wastewater, facilities/architecture, and construction management sectors.

    A challenging report card
    According to the American Society of Civil Engineers’ 2010 Report Card on Pennsylvania’s Infrastructure, aging wastewater management systems discharge billions of gallons of untreated sewage into Pennsylvania’s surface waters each year. Further, it is estimated that the state must invest $28.3 billion during the next 20 years to repair and upgrade existing systems to meet regulatory requirements. In early May 2011, Pennsylvania’s Commonwealth Financing Authority approved $172 million through the H2O PA program to fund 160 water and sewage infrastructure projects in 51 counties.

    Funkhouser said that most of the pipeline work will include subsurface, horizontal pipeline construction, including crossings under roadways, rivers, and streambeds and environmentally sensitive areas such as wetlands and parklands. This type of pipeline construction requires special equipment and capabilities. For example, Funkhouser cited a crossing of the Susquehanna River in Williamsport, Pa., a major project in which Buchart Horn was a consulting engineer. “Directional boring technology was needed to make this crossing,” he said. “We consider this a more cost-effective approach than using a cofferdam (watertight enclosures across the bottom), which can be compromised if you get heavy rains, for example, and then you have to start over from scratch.”

    Horizontal directional drilling allows precise installation of pipelines under obstructions such as roadways, waterways, and environmentally sensitive areas.

    Funkhouser described directional boring and other types of horizontal drilling to be a specialty that is provided by experts such as Aaron Enterprises. Aaron has worked with Buchart Horn on water and wastewater projects requiring tunneling and directional boring.

    “Even though horizontal drilling and boring are frequently the best approach to handling crossings, this is actually a niche capability,” explained Aaron Enterprises’ Rice. “We are essentially a horizontal drilling specialist, and the majority of our work is done through some type of trenchless technology.”

    Because most states will not permit pipeline construction contractors to open cut highways, the pipes must be sent under the highways to avoid problems such as traffic congestion and safety issues. Horizontal auger boring and directional drilling is also a solution to pipeline crossings of environmentally or historically sensitive areas where temporary trenching or running aboveground pipeline would be undesirable.

    Rice explained that there are a number of trenchless technologies used by specialists such as his firm. Pipe jacking, for example, allows the contractor to push pipe through a horizontally excavated hole. Pipe jacking is usually done for installation of concrete pipes.

    Specialty pipeline construction projects using trenchless technologies require experienced subcontractors with geological knowledge.

    “Pilot drill micro tunneling is another horizontal technique for jobs that require precise line and grade control,” Rice said. “That requires installing a small pilot opening using hollow steel rods. As you install them you monitor their horizontal and vertical positions by means of a theodolite survey instrument with a digital camera. Once the small-diameter rod reaches a target location, you attach to it a larger-diameter pipe and, as you thrust that larger-diameter pipe, the smaller one acts as a guide, making it go exactly where you want it to go. It gives you the ability to jack piping 400 feet, for example, and stay within a 1-inch tolerance.”

    One of the forms of horizontal drilling that will play an important role in replacing or expanding the pipeline infrastructures is direction drilling. Using the directional approach, the drill, located on the surface, enters the ground at a predefined angle and is electronically steered around obstacles.

    Aaron Enterprises has extensive experience using directional drilling for gravity sewer installations. Believed to be a world record, the firm used a specially modified, pit-mounted directional drill to complete a 900-foot-long gravity sewer bore through sandstone and red rock, maintaining a 0.0097 percent slope, then pulled back a 10-inch-diameter HDPE sewer pipe. The use of directional drilling on this project eliminated the necessity of drilling and blasting a 35-foot-deep open trench installation alongside existing water and gas mains. This saved the owner substantial money by eliminating the need for an additional sewer pump station, which will also save operational costs far into the future.

    “Using this method, we can’t make 90-degree turns,” Rice said, “but instead make a gradual, arcing turn over the length of the bore.”

    A Marcellus miracle?
    Directional drilling likely will facilitate installation of pipeline collection points and distribution crossings for the Marcellus gas industry that is now getting started in the Mid-Atlantic region. Exploration is already well underway in areas of Pennsylvania and West Virginia, so installation of a distribution network is an urgent matter.

    “You can’t always anticipate what you are going to run into,” Rice said, whose firm has more than 25 years experience in dealing with the terrains in Pennsylvania, West Virginia, Virginia, and Maryland. “In some instances, dealing with a combination of geological formations requires the use of multiple technologies. Even pipeline construction contractors who have the necessary equipment may not have the experience in our Marcellus regions or don’t want to get bogged down with this kind of work.”

    He added that unforeseen construction difficulties or inadequate handling of documentation required by local agencies can hamper pipeline construction progress of any type. Whether it concerns infrastructure repair, replacement, or new construction, delays over documentation or other compliance requirements will be costly and time consuming. Yet, experienced horizontal drilling and boring specialists who know the ropes and have the necessary equipment will likely enable pipeline contractors and engineers to save significant time and money.

    This article was contributed by Aaron Enterprises Inc. (www.aaronenterprises.com).