When it comes to trenching alternatives, there are 18-hp walk-behind (pedestrian) units that can dig a 4-ft.-deep by 6-in.-wide trench, and there are 120-hp ride-on units that can accomplish the same task. So which should you choose for your current job?

If you select a machine that's too small, you will sacrifice efficiency and could, in all likelihood, extend time on the jobsite beyond what is necessary. "Plus, it's harder on the user and the machine," says Tim Phelps, product manager, Barreto Mfg. "For example, if you're in rocks, the machine will want to hop around more. It's harder on the user because he has to do more of the work vs. the machine doing the job. Those vibrations are also hard on the machine."

Yet, if you choose a trencher that's oversized for the task, you could end up spending too much. "It's not a one size fits all market," says Greg Adkins, trench product manager, the Ditch Witch organization. "There are a variety of horsepower ranges and boom and chain options. It would be great if one worked for everyone, but Mother Nature doesn't work that way. We've had to come up with a number of ways to defeat her."

Evaluate ground conditions

When sizing a trencher, first evaluate the specifics of the job, i.e., how deep, how wide and how far the trench needs to be. That will easily narrow the field to a short list of a few models.

Next, evaluate ground conditions. "Learning about ground conditions is very important," says Bob Wren, Astec Underground. "It's probably more important than anything."

Ground conditions greatly affect productivity and the ability to efficiently move through the soil. "There's a big difference between doing a job in rock vs. one with good fill dirt," says Phelps. "If you're trenching in silty loam at 12 to 18 in. deep, I would recommend a smaller machine. It will be easier to handle, it will fit into tighter spaces and it will be less expensive to own and operate. On the other hand, if you're doing electrical lines 36 in. deep in tough conditions such as rock, clay or gumbo, you will need to consider something else."

A larger, higher horsepower machine gives you the ability to handle those difficult conditions more easily, because more horsepower means more torque to your digging chain, notes Jon Kuyers, utility product segment manager, Vermeer. This, in turn, gives you the ability to dig through difficult soil conditions such as caliche, sand, cobble and even rock.

"Generally, when you have more horsepower, you also have more weight," Kuyers adds. "All the components are larger and they're able to withstand more abuse and more difficult situations. The extra weight of the tractor also keeps the trencher boom in the ground and prevents it from bouncing around."

You may find that you have to oversize the trencher in certain ground conditions. ?Cobble and sand are very challenging applications,? says Adkins. ?You may need to dig deeper or wider than planned to accommodate carryover, which could necessitate the need for a larger machine.?

Do you need tracks?

Surface conditions also factor into the selection process. More manufacturers are offering units with rubber tracks. The benefits are two-fold: extra flotation to stay afloat in muddy conditions, and extra traction to pull through tough conditions.

With tires, there are only small points in contact with the ground. "You only have a few square feet on the ground at any one time," says Adkins. "With a track machine, you have considerably more, so the ground pressure is less and the machine will minimize turf damage."

The extra rubber on the ground also enhances performance. "If you can't pull the trencher through the ground and you're just spinning on tires, you're losing production," says Kuyers. "Tracks provide more traction when the ground is less than desirable. They're becoming more and more of a request.

"We've also noticed an increase in performance," he adds, "because the machine doesn't bounce as much as one on tires. That has increased production."