Grading and Excavation Contractor

That Is the Question. Or Is It?

By Randy Happel


	Guidelines for Trenching and Excavating

Over the past 35 years, Jimmy Vaughn has learned a thing or two about installing water and sewer lines. As founder and owner of Landform Construction, based in Mount Airy, NC, Vaughn and his crews have trenched through mucky wet clay, solid rock, and just about everything in between—often on the same job site. The challenging North Carolina terrain has taught Vaughn to expect the unexpected. It’s also taught him the importance of having a diversified fleet of equipment.

“There is no one tool that is perfect for every job,” Vaughn says. “We survey each job thoroughly when preparing a bid to make sure we have the proper equipment for whatever we might encounter. Most often that means a combination of approaches. Each project is different and every job site presents its own unique set of challenges.”

Mark Cooper, director of specialty excavation for Vermeer Manufacturing Co. agrees. “Most equipment is designed to do a specific task,” Cooper explains, “but there are some, like an excavator, that afford contractors greater flexibility because they can do several different things. As a result, many trenches have been dug with a hydraulic hammer that probably should have been completed with trenching equipment. Usually this happens when contractors are limited by the type of equipment they have in their fleet.”

Consider Leasing
The Landform fleet of equipment—comprising 25 machines—includes a trencher unit Vaughn uses for smaller trenching jobs. He recently leased a Vermeer T855 trencher for a project that the trencher in his fleet was too small to accommodate. The job involved a water line extension to an older, existing housing development established in the early 1900s. The area in and adjacent to the development was a quarry comprised of solid rock.

“It was a case of either having to blast or hammer rock in front of all these older houses,” said Vaughn, “so we made the decision to lease the Vermeer unit for this job and trench because blasting would have been too risky. We still had to excavate around some areas where cross lines and other obstacles existed, but trenching was still the best method to complete the project. It turned out to be very productive for us.”

Vaughn was happy with the average 500-feet-a-day production rates his crew was able to achieve using the trencher. He estimates the trencher unit outperformed a hydraulic hammer by almost double. Plus, he was able to use a lot of the trenching spoil for backfill.

“It worked out great for us,” Vaughn explained. “We still needed to have an excavator on site to place the pipe, but the process was very smooth.”

Perception not Necessarily Reality
Cooper is concerned about the perception that trenching equipment costs more to operate than other equipment, such as an excavator with a hydraulic hammer attachment. Contractors often shy away from using trenching equipment because they may assume it costs more to operate a trencher per hour than an excavator and hammer. But Cooper encourages contractors to focus more on the big picture which also takes into account production rates, not just the single cost-per-hour factor.

“The greatest obstacle staring in the face of a trenching unit is cost per hour,” Cooper explains. “It may be true that the operational cost per hour will be more than with an excavator and hammer, but no one is getting paid by how many hours they work. It’s about how much ditch is actually opened and the amount of pipe put down within that hour. It’s about finishing fast, and at the end of the day, trenching should actually cost the contractor less.”

More Controllable Results
Another big advantage for contractors is that, because of the fewer variables, they can prepare more accurate bids using trenching equipment. Take hauling costs for example. A trenching unit will create a clean, consistent vertical wall, while an excavator/hammer method will likely result in more of a “V” shaped trench. This will require purchasing more material to close the trench once the pipe is in place.

In addition, it is difficult to control spoil size from a hydraulic hammer, whereas the spoil from a trenching unit will be consistent in size, much of which can be used for backfill. This reduces hauling costs for removing spoil that is unusable and costs for trucking in additional backfill.

All of this adds unnecessary costs to the job.

“The trenching unit will give contractors a much more manageable result,” explains Cooper, “with more control over logistics and less room for unexpected costs after a bid has been accepted and locked in. Knowing the dimensions of the trench up front allows contractors to calculate the amount of usable spoil, hauling costs and backfilling costs in advance—without many surprises. This is a tremendous advantage over hammers where the configuration of the ditch is hard to control.”

So, why wouldn’t a contractor use a trenching unit?

According to Vaughn, trench width is the biggest factor in determining whether to use trenching equipment or the excavator/hydraulic hammer approach. The wider and deeper the trench, the more capital costs incurred. If a contractor doesn’t own a trenching unit capable of completing wider trenching projects, they tend to opt for the excavator and hammer because nearly every contractor has such equipment in their fleet. Many contractors can’t justify the capital expenditure to purchase a large trenching unit unless the majority of the projects they complete are larger in size.

But as Vaughn discovered when taking on the project in the older subdivision, leasing larger equipment is a viable option contractors can profit from by building the leasing costs into the project bid. And given that there are more factors within their control when trenching, the leasing option can be very lucrative.

“There is a definite place for both types of equipment in a contractor’s fleet,” asserts Cooper. “An excavator is more versatile. It can pick up and place pipe and claw its way around obstacles that a trencher can’t. But when it comes to cutting a ditch, nothing does it better or more efficiently than a trencher.”

Randy Happel is a features writer based in Des Moines, Iowa.

GEC - May 2008

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