For all the high-tech, manmade gadgetry available for locating and identifying buried utilities, nothing is more reliable than what Mother Nature provides us in abundance: water. Water is the main ingredient in potholing, the act of physically uncovering a buried utility to verify its location. Potholing is widely held as the surest, safest method of determining a utility’s exact position.

And it’s probably safe to say that the more that utilities are verified in this manner, the fewer accidental utility strikes there would be each year. Estimates vary because many strikes are not reported, but accidental strikes are believed to number in the hundreds of thousands annually.

The Common Ground Alliance (CGA), the organization dedicated to preventing damage to underground infrastructure, keeps track of the strikes reported by its member organizations. The official CGA figure for 2009 (the latest currently available) is 115,232. This is a 15 percent decrease from 2008, and marks the first time since the 2003 launching of the CGA’s Damage Information Reporting Tool (DIRT) that this figure decreased from one year to the next.

Good news, right? It depends. The CGA’s 2009 DIRT Report cautions that this “decrease may be the result of several factors, including the reality [of] economic conditions and less construction activity.”

Whatever the reason, the figure 115,232 represents a significant reduction. But it is still way, way too large a number, considering the technology we have available for preventing accidents, and considering what even one utility strike can mean: disruption of essential services, expensive and time-consuming repairs, lawsuits, injuries, and even death.

Because of accelerated efforts to prevent damage to buried utilities, potholing is becoming a standard practice on a growing number of utility jobsites. A great deal of credit goes to the CGA’s marketing efforts and its identification and dissemination of construction industry best practices, considered to be the most thorough and effective guidelines for preventing damage to underground facilities. Government agencies are adopting regulations that require potholing, and project owners and contractors are establishing their own policies specifying potholing before excavation or directional drilling begins.

Seeing Is Knowing.

Potholing is not new. For years, the process consisted of workers using shovels, a slow and labor-intensive job that was not without risks. Even the most skilled and experienced laborers made mistakes, often at the end of a long, hot day when fatigue had set in. To speed the process, workers began using backhoes, but in many cases this technique only reduced the time it took to cut through an electric cable or water line.

Vacuum excavators revolutionized the potholing process. When they were introduced, vacs were primarily used for removing fluids and spoils from horizontal directional drilling sites, and various municipal tasks such as water-leak repair and cleaning out storm drains, valve boxes, and utility vaults. Then vac systems’ “soft” excavation (or hydro excavation) capabilities began to catch on. Digging postholes for new fence installation was a snap with a high-pressure stream of water. And if postholes, why not potholes?

Most vacuum excavators are equipped with high-pressure air or water, which is directed by a wand with a special tip to displace soil. With high-pressure water, a vac system can quickly create small, precisely controlled potholes to uncover buried utilities. Using proper techniques, the risk of damage inherent with a backhoe, excavator, or other mechanical tool can be reduced. Depending on soil conditions, a vacuum excavator can complete a 12-inch-square, five-foot-deep pothole in fewer than 30 minutes. Spoil from the potholing process then can be simultaneously vacuumed to a holding tank for reuse or disposal.

Vacuum excavators are capable of “digging” much deeper than six feet, but utility potholes seldom need to be more than that. And the small excavation is easier, faster, and less expensive to repair.

Reducing Risk Also Reduces Expense.

That’s right: done properly, potholing is not only safer, but the actual process of potholing with a vacuum excavator is also less expensive. Santa Clarita Valley, California, is among the growing number of municipalities that have discovered the economic benefits of potholing.

Like most American communities, Santa Clarita has a utility infrastructure that is showing its age, and the city has no choice but to replace it, section by section, as funds allow. In 2008, the City of Santa Clarita made the decision to invest nearly $50,000 in a state-of-the-art vacuum excavation system to perform, among other things, the task of potholing to safely determine where and where not to excavate.

After looking at the costs of potholing with a vacuum excavator versus the traditional, labor-intensive method, the decision was easy. Crunching the numbers, city officials estimated that the typical cost of digging 10 potholes with a backhoe was $7185, itemized this way:

• $2400 for paving roughly 200 square feet
• $3885 for 30 hours of labor
• $900 for 30 hours of equipment use

The same job with a new vacuum excavation machine, however, was estimated at only $1875, or roughly a quarter of the cost of potholing the old-fashioned way. Only 40 square feet of paving would be required, and only 10 hours of labor and 10 hours of equipment use costs.

Needless to say, the vacuum excavator was a smart investment for the City of Santa Clarita, and would be for any community or company interested in locating utilities with minimal risk and expense. This would seem to include everyone in the underground construction industry, and there is a vacuum excavator for every budget—from the portable vac that can fit in the back of a standard-size pickup truck, to the trailer-mounted systems, to the large, diesel-powered, skid-mounted vacs with 1200-gallon water tanks, hydraulic booms, and many other options and accessories.

For those not ready to buy, an affordable strategy is rental, and many equipment rental companies carry vac systems. Whether you buy or rent, be forewarned: after trying the potholing method to expose utilities, after experiencing its speed, efficiency, economic and safety benefits, you might not want to go back to the old way of doing things.

Sources for this article:  

• Common Ground Alliance 2009 DIRT Report  
• Commongroundalliance.com  
• Compact Equipment article, April 2009: “Hydro Excavation Systems Provide Precise, Safe Utility Location,” by Barb Cooper.
• Santa Clarita Valley Signal article, November 2008: “Water Retailer Finds A ‘Hole New Way To Work,” by Jim Holt.
• Ditchwitch.com pressroom articles: “Vacuum Excavators,” “The ABCs of Utility Damage Prevention,” and “Best Practices For Damage Prevention.”