Expert Q&A: Dennis Doherty on trenchless engineering
Dennis Doherty is the national practice leader for trenchless technology at Haley & Aldrich, and has over 25 years of experience in the field.
Do you think trenchless technology is well understood in the marketplace, or is it something new to most people?
It’s becoming better understood all the time. However, there are still a lot of people who just have a general idea of how advanced trenchless technologies have become, and because of that they assume that designing a trenchless project is as simple as drawing a line on a map.
But that’s just not the case. The success of the project always comes down to the expertise of the people planning and executing it. Getting the design right is the real art, and so a big part of ensuring a project’s success is educating the owners, and sometimes even the engineers about the things they need to consider in advance.
What kinds of things should people consider in advance?
The most critical factor in a successful drill is understanding the subsurface conditions. The subsurface issues are so sensitive, and our ability to detect them in advance is now so good that the right geotechnical survey information sets the project up for success. Unfortunately, many times people try to save money on this part without realizing how badly it can come back to bite them later in the form of change orders or even project failure.
Depending on the project, you also need to consider environmental and sustainability issues, existing infrastructure, nearby buildings, set-up space, permits, interruption of street and pedestrian traffic – or if it’s under a waterway, you have to consider marine habitats, boat traffic, and so on.
So, trenchless technology is really just one part of a bigger puzzle?
There really is a lot to it. I recently worked on the project to update the ASCE Microtunneling Guidelines, which were last issued in 2001. The finished document we published in April 2015 was three times the length of the previous version. There was that much advancement in the field.
And, as much as we updated the construction best practices, there was even more added information on managing risk, understanding the full range of issues, and making clear what owners, engineers, and contractors each need to bring to the party to operate at a professional level.
What is unique about the way Haley & Aldrich approaches trenchless projects?
We’ve been talking about risk, and I think that’s really the key. Designing to remove risk is the most important thing.
There is a wide range of underground issues that can affect your project performance, as well as all of the aboveground issues I’ve mentioned, and so I think of it the same way Michelangelo did about his sculpture when he said that he’d start with a huge stone and then carve away anything that wasn’t statue.
That’s the same kind of approach we take when designing a project. Once you understand the client’s objective, you get all the facts on the table and then start removing the risk – all the things that are likely to cause problems. What you have left is the optimal solution to achieve the client’s objective. And it really comes down to that. From start to finish, we’re helping our client feel like they are in control of what could be a risky endeavor.
For more information about Trenchless Engineering, contact Dennis Doherty.