World Trenchless Day: Voices from Our Horizontal Experts

As engineers focused on underground infrastructure, we can easily compare ourselves to carpenters bringing a full ‘toolbox’ of solutions to every new infrastructure problem we encounter. While open-cut construction methods for pipe installation have been around since the earliest civilizations, the emergence of trenchless technologies in the underground infrastructure industry has given engineers countless new tools to solve complex problems. 

The term trenchless technology refers to a family of techniques for assessing, installing, or rehabilitating underground infrastructure with limited disruption to the ground surface. That family of trenchless techniques includes new installation methods such as tunneling, horizontal earth boring, and pipe jacking; renewal methods such as cured-in-place pipe lining, sliplining, and spray-on linings; and assessment methods such as closed circuit television inspection. Selecting the best method is a function of many factors including pipe size, use, shape, depth, alignment, environment, structural needs, loads, flow capacity, condition of existing pipe, number of services, surface impact, equipment laydown areas, time, and, of course, money. 

In honor of World Trenchless Day, we wanted to share a few examples of how Woodard & Curran selected the right trenchless solution to help communities minimize social, environmental and economic impacts for emergency infrastructure replacement:

Pipe bursting along the coast

A 200-foot stretch of 18-inch vitrified clay gravity sewer pipe (VCP) was found to be 50% collapsed in a coastal resource area. A complete failure would mean a significant and extended duration overflow event into the tidal resource area. Instead of recommending an open cut excavation with cut depths exceeding 18 feet, We recommended and designed a replacement using pipe bursting. The project entailed excavating two 20-foot access pits in lieu of a 200-foot excavation. The trenchless solution was completed in three days for 50% less money than the seven-day estimate for the open-cut option. The environmental impacts were substantially reduced by limiting the excavating in the tidal resource area. 

Cured-in-place-pipe under manufacturing facility 

A 300-foot segment of 30-inch VCP interceptor sewer that conveyed water beneath a manufacturing facility was showing signs of structural failure. A complete failure would have resulted in an extended duration bypass while a new route could be designed and installed. In advance of failure, We recommended the pipe be rehabilitated with a cured-in-place pipe (CIPP) liner that could be installed from the existing manholes located on either side of the manufacturing facility. The CIPP work was completed in one day for substantially less than rerouting 300 LF of 36-inch sewer. The manufacturing facility was not impacted by the trenchless rehabilitation and extended detours or road closures were not required as part of the solution. 

Sliplining under a major California Highway

A 500-foot stretch of an existing 24-inch cast iron water transmission main crossing beneath a busy highway in Antioch, California was leaking and had the potential to undermine the roadway and wreak havok on the morning commute.  Obviously, an open cut solution was out of the question.  Instead, we conducted an alternatives analysis and recommended that the pipe be sliplined with fusible PVC.  The work was completed quickly and with zero change orders. and heavy commute traffic was not impacted during construction.  

These are just a few examples of how the right engineering solution can save communities both time and money. Education of both our own personnel and our clients is the key to our future success in the trenchless technology marketplace.


Justin deMello Client Manager Water

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