Subsurface Utilities

The scene is a contractor’s worst nightmare. A backhoe in Newark, NJ, claws into an unmarked, 4,000-volt power cable, setting off an explosion that burns vehicles, causes smoke inhalation for a dozen people, and disrupts power to nearby buildings and traffic lights. Although construction crews had dutifully checked utility maps for potential obstructions, no one could have guessed the danger awaiting workers until it was too late.

Whether the obstacle is a cable or a water line, engineers, contractors, and construction managers are constantly reminded that what’s in the ground may not be on their maps. Uncovering what lies beneath project sites minimizes the potential costs associated with injury, property damage, or schedule delays.

In recent months, KCI’s Subsurface Utility Engineering (SUE) Units in Maryland and North Carolina have been working with public and private sector clients to provide a more complete understanding of existing subsurface utility infrastructure. The teams use vacuum excavation and ground penetrating radar (GPR) to locate, designate, and map features. The vacuum trucks excavate soils in test pits as narrow as one foot in circumference and as deep as 35 feet. The system also may be used to excavate soils in confined spaces, with limited access. GPR, one of the most powerful remote, non-invasive sensing instruments available, helps KCI detect metallic objects, such as storage tanks and piping; rubber; and geological features, including soil and shallow rock strata, sink holes, and voids.

KCI’s SUE units work closely with surveyors, engineers, designers, and construction managers throughout the company, integrating global positioning system (GPS) surveying technology with CADD and Geographic Information System (GIS) data management tools to provide subsurface utility mapping. Using layers of GIS and CADD data, KCI can develop innovative solutions early in a project’s design phase. SUE crews also work closely with KCI’s Public Utilities inspectors to conduct connectivity studies, documenting the relationships among utility lines in manholes and other underground facilities for large carriers.

KCI’s David L. Quickle is overseeing several SUE projects for the North Carolina Department of Transportation under a one-year, full-service contract and sees the benefits of investing in SUE. “Many DOTs have conducted cost benefit studies to estimate the potential savings and other advantages of using SUE in a project’s early design phase. If you have an accurate utility map, it’s possible to shift a proposed structure slightly to minimize or sometimes avoid a utility relocation altogether.” Quickle added that this ability can virtually eliminate mid-construction delays because of unknown or misrepresented utilities, which translates into tremendous savings in time and money for the client.

“The Tennessee DOT is at this point with its SUE program,” Quickle said. “KCI has completed the designating and is waiting on the test hole requests on two test projects in the Knoxville area.”

KCI’s Mid-Atlantic SUE manager, Douglas F. Bock, sees similar advantages. “The Federal Highway Administration has published several case studies quantifying the value of SUE. We know of one roadway project for the Maryland State Highway Administration, where more than a mile of utilities conflicted with the widening design. MSHA used SUE to make slight design modifications that avoided all but 400 feet of the utilities. The investigation cost the client about $56,000, but ended up saving MSHA and the utilities more than $1.3 million.” A recent cost analysis by the Federal Highway Administration of 71 projects valued at $1 billion found that for every $1 spent on SUE, FHWA realized $4.62 in cost savings.

Quickle added, “Having an in-house SUE capability helps us help our customers. In Pennsylvania, recently, we were able to provide SUE services as part of a bridge design project for PENNDOT. In the past, we would have had to select a subconsultant to perform the work. Our responsiveness makes for a better partnership and a better overall project.”


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