Surveyors are experts at depicting the size, shape and location of features on the ground. However, we are limited to locating what we can see. For some projects, surveys that are limited to visible improvements above ground do not provide enough information for design and engineering work. In order to preserve existing infrastructure below ground level, it is necessary to determine accurate locations of utilities under a jobsite. Many third-party companies specialize in locating subsurface utilities, but our progressive surveying and engineering firm in Florida learned to offer this capability in-house to better serve our clients.
At Calvin Giordano & Associates (CGA) of Fort Lauderdale, Fla., we consistently strive to improve our services and exceed our clients' expectations. Our large surveying and engineering departments interact closely on various projects, so members of both teams are aware of the coordination and delay problems associated with contracting out subsurface utility location. CGA decided to offer this service in-house because we wanted to obtain more accurate results, avoid liability and keep projects on the company's own timetable. CGA is proud of the one-stop shopping environment we offer clients; our 115 employees provide planning, civil engineering, transportation/traffic engineering, surveying, permitting, environmental specialty, landscape architecture, data technologies and GIS development, and construction services. Additionally, CGA has now invested in a vacuum excavation system that allows us to provide clients one more service: efficient and accurate utility location with minimal damage to the surrounding area.
A Demo Does the TrickContinuously seeking ways to improve CGA's offerings, John Downes, PE, a principal at CGA, along with Joe Aldacosta, PSM, director of survey, and Ronnie Furniss, PSM, field crew supervisor, discussed a non-obtrusive method of locating underground infrastructure. After some research, they set up a demo for a device called the VaXcavator from Vacuum Source Inc. (VSI) of Greer, S.C. A slurry excavation system providing a non-destructive solution for exposing existing utilities, the VaXcavator allows operations to determine the depth of existing underground utilities without destructive excavation or boring procedures. By combining a powerful suctioning vacuum with high-pressure water jets, the VaXcavator allows the creation of a pothole with minimal impact to the surrounding area. This type of limited underground excavation, frequently called "potholing," reduces costly surface restoration and allows surveyors to accurately locate utilities.
At the demo, Downes saw that the VaXcavator could perform as advertised and was convinced it would be a smart investment for the firm. "I had been watching that type of equipment for years," Downes says. "Most of the equipment is big and bulky and sits on large trucks, but this vacuum is more compact and carried on a trailer [behind a pickup truck]." CGA bought the device-a Model VT500DSJ-on the spot for approximately $38,000. As a new capability, CGA expects vacuum excavation to be included in many of its future contracts.
Creating the VaXcavator CrewOther engineering firms offer underground excavation, and have generally created separate departments for this service. CGA's VaXcavator was assigned to the surveying department for a few significant reasons. A surveying crew usually needs to accompany the VaXcava-tor onsite to obtain the measurements of exposed utilities. Rather than hire new personnel, we drew from our surveying department's existing pool of field personnel to create the VaXcavator crew. Because we trained a surveying crew to operate the vacuum equipment, a single crew has the expertise to both uncover and locate the buried objects.
As it turns out, the single crew is one of the best benefits of owning the VaXcavator. We no longer have to coordinate with a subcontracted crew from another company for utility location. This means there are no scheduling worries or delays, and, with our own surveyors performing the excavation, it's a given that the information needed to get the job done will be collected. The surveyors know what they need in order to get an accurate shot at a pipe or other utility, and they can obtain accurate elevations because they perform the preceding excavation. Additionally, the single crew removes the liability incurred when an excavating crew leaves holes in the ground while waiting for a second crew to arrive to the site to get locations. With one crew excavating and locating the utilities, the holes are covered up before anyone leaves the site.
Training for Success and SafetyThe first projects that utilized the VaXcavator were part of a land development project in Miramar, Fla. VSI training personnel instructed CGA's employees on the equipment and procedures. The trainers spent two days teaching the crew hands-on operation and maintenance, from the digging and filling of holes to the after-care and cleaning of the machine.
The crew first learned the two types of digging methods: wet and dry. The VaXcavator is essentially a giant vacuum with four attached pressure hoses. Deciding whether to use a wet dig or dry dig to expose utilities depends on the soil type at the excavation site, VSI trainers explained. A dry dig is best on sand; a wet dig that uses the pressure hoses is better for areas with lots of rocks or compact soil. To begin a dig, the crew removes the grass or asphalt covering the surface above the utility and digs a small hole (generally eight to 12 inches in diameter) with a post hole digger. The remaining dirt covering the utility is sucked up by the VaXcavator; the surveyors can then locate the subsurface utilities.
After the excavation, the VSI trainers taught the CGA crew how to restore the site. This included how to dump the VaXcavator's bucket to refill the potholes. The crew carries additional sand with them on every job to make sure there are no depressions left behind from the dig. VSI's training emphasized safe practices, such as securing the VaXcavator's latch to protect bystanders when unloading the system's dumpster. Crew members were instructed to be vigilant when using the pressure jets, especially when other people are nearby. Safety gear was also discussed; crew members must wear insulated boots and gloves when digging in case they expose any electric lines.
Ed Walden, party chief of the VaXcavator crew, says, "Now that the crew has become accustomed to different types of soil, they know what to expect and how to handle each scenario."
Putting the VaXcavator to WorkIn addition to the initial project CGA conducted with the VaXcavator for land development in Miramar, the new system has been put to use gathering water main locations for a roadway project in Lantana. On both projects, the VaXcavator was used to resolve possible conflicts from existing utilities and proposed utilities. In Miramar, we located a water main and some gate valves to prevent a possible conflict with a proposed sewer main. In Lantana, water main tie-ins and a force main were found to prevent a conflict with a proposed storm drainage system. The engineer on the Lantana project was extremely pleased at the effectiveness of the dig and the timeliness of the information he received from CGA for his design.
The VaXcavator is also being used on a roadway widening project on Pines Boulevard in Pembroke Pines for the Florida Department of Transportation. The road has been redesigned, and large mast arms are going to replace the older, conventional wire-held traffic signals. These mast arms have large concrete bases that require placement clear of utilities. Because utilities can only be located within a few feet using utility company as-builts, CGA employs the VaXcavator to expose the actual infrastructure and locate utilities at the proposed base location with survey accuracy for design purposes. Normally, engineers send their plans to the utility companies, who in turn mark the plans with estimated utility locations. Due to the inherent inaccuracy of this process, conflicts are invariably discovered in the field that lead to change orders for the contractors and redesigns for the engineers. Because of its increased accuracy in locating utilities, the VaXcavator's use is expected to save a great deal of time and money on this project.