kim staheli

Dr. Kim Staheli, P.E.



The year of 2015 has been very exciting and intriguing for the trenchless technology industry. Because there are literally thousands of cities with miles of pipelines in bad repair or simply have undersized pipelines to house their flows, the trenchless rehabilitation market has continued to grow and thrive.

Often pipeline rehabilitation methods offer the most cost-effective solution for repairing or upsizing these pipelines. Within the rehabilitation sub-category of trenchless, there have also been great amounts of pressure pipe rehabilitation as advances in this technology have gone from very rare to almost commonplace in the industry. Of note, we see more people attending the Water Rehabilitation sessions at NASTT’s No-Dig Conference, than any other technical sessions, clearly showing that pressure pipeline rehabilitation remains a very hot topic in the United States and Canada.

Having said all of this, you would be incorrect to think that the new installation market is slow. In fact, the industry has seen a lot of quantity and quality trenchless designs within the new installations market. During the last quarter of 2015, trenchless designers have found themselves extremely busy trying to keep up with the design budgets of the large scale owners up and down the West Coast where there is a high call for new pipelines that contain trenchless segments requiring design.

Another trend in the new installation market is to marry different trenchless technologies to allow less precise trenchless methods to accomplish more precise line and grade requirements than would normally be expected with the host technique. For example, it is widely known that auger boring has a proven history of installing steel casings under a variety of circumstances and in places where open-cut would not be acceptable. However, auger boring may not be a good choice if line and grade sensitivity of the pipe exists. One option would be to move away from auger boring all together — changing the base technique to a technology such as microtunneling, which could result in a marked increase in project cost. Instead, one might consider the addition of pilot tubes to auger boring. A pilot tube rig could be driven from the beginning to the end of the drive, setting the delicate line and grade, and then following the pilot tubes with auger boring when the precise grade has already been set. The combination of pilot tubes with auger boring is generally much more cost-effective then moving to microtunneling.

Another trend in the industry is specifying pipe ramming through which gravity pipelines will be placed. This method is still very much in its infancy and a balance is trying to be achieved to determine the proper upsize on the rammed casing to ensure that there is enough space between the rammed casing and the product pipe to obtain the desired grade. Certainly this is a function of the length of the ram and the density of the soil through which the pipe is being rammed. However, when successful, this method can offer a very economical installation solution for a gravity pipeline at a very shallow slope for a trenchless method. Also, it may be beneficial to use pilot tubes with pipe ramming to allow the pipe ram to be installed at an appropriate line and grade to minimize the size of casing that must be installed to achieve the desired line and grade on the carrier pipe; however, the geotechnical conditions must be well known and a proper geotechnical investigation must be completed during design and for construction documents.

Another trend is the use of pilot tube equipment that is pushed between two manholes. A small-diameter directional drill rig is then drilled from the surface into the manhole and the drill pipe replaces the pilot tube pipe that has been placed to the precise line and grade. At the far manhole, where the pilot tube has been completely replaced, the pilot tube is drilled to the surface. At the surface, a small reamer is attached to the drill pipe and a small product pipe, typically HDPE, which is then pulled back. The drill pipe is upsized (at the precise location that has been established by the pilot tubes) and the HDPE pipeline has been installed to the appropriate grade. One very important feature of this method is that the drilling mud is collected at the lowest manhole location, allowing for a natural pressure release location, and avoiding drilling pressure build-up during the HDD operations. This method allows the use of HDD technology to install small diameter HDPE pipelines at inner-city locations without the fear of hydro-fracture or loss of grade. This is all accomplished by pairing precise grade pilot tube technology and small diameter HDD technology.

With the number of old deteriorating pipes that are currently in the ground and the immediate need for new pipelines that can carry higher volume flows, the population increases in the metropolitan areas, and increasing environmentally sensitive environmental areas, trenchless techniques are going to continue to evolve and grow. With the talented and innovative people that we are lucky to have in the trenchless industry, I am sure that trenchless technology will continue to advance at a lightning pace to keep up with the demands of the future.

One of the things in which I am proudest to lead the NASTT is the “New Product Innovation Award” that is given every year. What is amazing to me is the number of quality candidates from which to choose. That is a tribute to the many people working passionately to improve the industry and keep up with the demanding pace at which it’s moving forward.  I don’t know what the next new thing will be, but I am excited to find out as we launch into 2016.

 

Dr. Kim Staheli, Ph.D, P.E., is president of Staheli Trenchless Consultants and is the chair of the North American Society for Trenchless Technology (NASTT).