Published July 2007

The World Below

By Ted J. Rulseh (page 8)

The scope and ingenuity of trenchless technology keeps pushing the technology toward a dominant role in pipe installation and repair.

If you question the value of trenchless technology, there’s a web site you should look at. The International Society for Trenchless Technology has an interesting series of diagrams at www.istt.com.

Click on the “Why Trenchless?” tab and you’ll see an aerial view of a major downtown city intersection with traffic moving smoothly. Then the same view with the streets and traffic cut away, to show all the buried utilities. Then the same view with the intersection torn up for a major repair.

Needless to say, not much traffic is moving. And there, in a nutshell, is the argument for trenchless. It’s not necessarily the hard cost of trenchless versus the hard cost of dig-and-replace that makes the difference. It’s the avoidance of disruption.

Keeping people happy

Any municipal manager knows that nothing makes people unhappier than getting stuck in traffic at a construction zone, or having to look at and deal with open trenches for days on end while a repair is completed in an otherwise picturesque neighborhood.

Trenchless methods eliminate most of the disruption. Some still require digging, of course — entry and exits pits are necessary to some technologies. But some methods, like manhole-to-manhole cured-in-place lining, require no digging at all.

Two things are noteworthy about trenchless methods. First is the sheer variety of tools, materials and techniques available. Some of these are described in this issue of Municipal Sewer & Water.

For sewer repairs alone, we have grouting, cured-in-place pipe (CIPP) lining, slip-lining and pipe bursting, each with variations on the basic theme to suit different pipe sizes and materials.

CIPP and slip-lining also work for water mains. Bursting systems can slice their way right through tough materials like cast iron. It’s even possible to burst old pipe and pull into place pre-sterilized mains. In addition, there are a variety of spray-on liners for water mains — cements, epoxies and others.

All that is to say nothing of installation methods, like microtunneling, horizontal directional drilling, and jacking and boring (for installing steel pipe casings under railways and road embankments).

Full speed ahead

The second noteworthy thing about trenchless is the steady advancement in the state of the art. Entire national and international trade shows are dedicated to the technologies. Our own Pumper & Cleaner Environmental Expo includes a heavy concentration of trenchless providers.

Each year, we see manufacturers introducing new products — better bursting systems and liners, more sophisticated boring tools, and new kinds of piping. We also see new companies coming into the business, offering new methods that make repairs faster, easier and longer-lasting.

Among notable additions in recent years are methods of CIPP spot repair and ways of sealing the lateral-to-main junction in full-length line rehabilitation. As trenchless methods get better, and as new methods emerge, it becomes all the more essential to evaluate trenchless against digging for any given project.

Take a close look

Excavators, backhoes and trenchers will never go obsolete — there will always be pipes that can’t be installed or repaired any other way, and there will always be cases where traditional methods are simply the most cost-effective.

Still, for many communities and utilities, the time has come to rethink the decision points — the boundaries between open-trench and trenchless — for any given job. Before an excavator’s bucket teeth hit the ground, perhaps it’s worth asking: Have we examined all the trenchless options? Should we look once more at the latest tools available? What really is the cost difference between trenchless and open cut?

Have we considered all the costs? Not just the price of the construction itself, but the intangibles of community convenience and good will?

Think about that aerial view of a downtown intersection — a big trench in the street and traffic snarled up in all directions. Then think of how that same intersection would look if trenchless methods were used — which is to say, much the same as if no construction were under way.

Then, for any given project, consider asking: What if we went trenchless?

Comments on this column or about any article in this publication may be directed to editor Ted J. Rulseh, 800/257-7222; editor@mswmag.com.