NASTT is pleased to announce the winners of the 2023 NASTT Outstanding Trenchless Paper Awards for New Installations and Rehabilitation. These awards recognize excellence by commending authors of the best NASTT No-Dig Show papers each year. The winning papers were presented at the NASTT 2023 No-Dig Show.

Download the winning papers bundle or the full conference proceedings in the NASTT Online Store.

Authors of both papers will give encore presentations at the NASTT 2024 No-Dig Show in Providence, Rhode Island.

NASTT 2023 Outstanding Paper – New Installation

The Use of a Geo Pilot Bore to Confirm HDD Feasibility

James Murphy, M.Eng. P.Eng., UniversalPegasus International, Calgary, Alberta

Dan Costello, M.Sc. (Hons), P.Geo., PMP. BGC Engineering Inc., Vancouver, BC

Marty Zaleski, M.Sc., P.Geo, CEG, LEG. BGC Engineering Inc., Vancouver, BC

About the Authors. For James Murphy, it all started back in the summer of 1972 when he was a student working on the Toronto subway tunnel construction project. “I gained an appreciation for soils and soil mechanics,” he said. “This ultimately led to a career in major pipeline design and construction and then a specialization in trenchless technology.” In 2011 the paths of the authors put them on a team working on the TMEP pipeline project which they recognized was going to be extremely challenging from a major trenchless standpoint.  They used their ingenuity to demonstrate that these specific crossings were possible using the Horizontal Directional Drilling technology and would likely be the most cost-effective way to meet the challenges presented by the geography and the geology. “The design of trenchless crossings was a natural extension of the work I do to develop and interrogate geological models, using tools that span geology, geotechnics, and geophysics, Marty Zaleski explained. “The key challenge is making reliable predictions of ground conditions in the context of sparse observation points, which requires that we understand depositional processes and devise new ways of collecting meaningful observations. This is where geologists shine.” The whole team shone brightly in Portland and want to acknowledge Rob Brown, President of Universal Pegasus, Alex Baumgard, BGC Geotechnical Engineering, Manjiri Khare, Project Manager Universal Pegasus for their support.

Abstract. Within the Trenchless Program for the Trans Mountain Expansion Project almost 50 Horizontal Directional Drills (HDDs) as well as all the other trenchless methods were utilized. However due to severe topography and access constraints, there were locations where a geotechnical investigation with a normal number of boreholes would not be able to provide sufficient geotechnical information and even a limited number of holes would be cost prohibitive. Boreholes in some cases would have been hundreds of meters deep with difficult access and site preparation. Also, from a design standpoint, engineering would primarily be interested in whether there are fractures that would be major fluid loss zones or there would be fractures or faults that would produce water that would likely fail the HDD. Therefore, for two long ‘potential’ NPS 36, HDD crossings in mountainous terrain, Universal Pegasus offered up the potential for doing ‘geo-pilot bores’ to confirm the feasibility of using HDD in these locations. From a regulatory perspective, a geo-pilot bore following the HDD design profile is considered part of the geotechnical program provided it does not exit and stops short by 50 metres or more. Exiting the bore would constitute “construction” which has significant restrictions and reporting issues.

A successful geo-pilot bore approximately 1,700 m (5,600 ft) long confirmed the feasibility of the first HDD crossing at Dry Gulch in August of 2021 and a second geo-pilot bore for the Mountain Crossing #3 HDD crossing, approximately 1,600 m (5,300 ft) long HDD was completed in 2022. This paper describes the design, thinking, and construction challenges behind the geo-pilot bore concept with these two examples.