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Room for Improvement
Non-destructive methods that manually determine a utility are considered “safe excavation practices” in 38 states, according to the Common Ground Alliance (CGA), a Virginia-based, non-profit organization that advocates for safer digging practices. Every state has a call-before-you-dig hotline. Still, the CGA estimates there are between 500,000 and 750,000 accidental strikes of underground utilities each year in the United States.
That number could be reduced to nearly zero. There are four SUE Quality Levels, with each level providing an additional, more-detailed layer of due diligence and protection.
The Costs and Ripple Effects of a Damaged Utility
• Potential injury and death
• Criminal investigations
• Environmental contamination
• Project delays
• Lost time and productivity
• Financial liability
• Redesign costs
• Higher construction bids
• Change orders
• Extra work orders
• Construction claims
• Higher insurance costs
• Higher fi nancing costs
• Detours
• Bad publicity |
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These Quality Levels, described in the Standard Guideline for the Collection and Depiction of Existing Subsurface Utility Data, were developed by the American Society of Civil Engineers (ASCE). This National Consensus Standard (NCS) follows the legal procedures for adoption not only as an ASCE standard but also as an American National Standard Institute (ANSI) standard. Courts and lawyers use these standards to assist in both defining a professional’s standard of care and in assigning blame. The Federal Highway Administration (FHWA) and many state DOTs support these standards as best practices. The Quality Levels are:
Quality Level D (QL-D) — involves utility records research and interviews with knowledgeable utility personnel.
Quality Level C (QL-C) — involves surface survey, identifying and recording aboveground features of subsurface utilities such as manholes, valves and hydrants.
Quality Level B (QL-B) — involves application of “surface geophysical methods” such as electromagnetic-based locating instruments, ground penetrating radar, radar tomography, metal detectors and optical instruments to gather and record approximate horizontal (and, in some cases, vertical) positional data.
Quality Level A (QL-A) — involves physical exposure via “soft-digging” (vacuum excavation or hand digging) and provides precise horizontal and vertical positional data.
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| An ounce of prevention really is worth a pound of cure. A Purdue University study found that for every $1 spent on SUE methods, $4.62 was saved. In that vein, North Carolina’s DOT spent $10,000 but saved an estimated $500,000 using vacuum excavation for a project to locate a water line. |
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So, what does all of this mean? According to the FHWA, the intent of this standard is to present a system of classifying the quality of the existing subsurface utility data. Such a classification allows the project owner, engineer and contractor to develop strategies to reduce or, at a minimum, allocate risk.
It also means the engineer needs to know the appropriate recommendations to make to the project owner and the engineer will likely be held responsible for negligent errors and/or omissions in the utility data at the certified Quality Level. Ultimately, the project owner decides which Quality Level he or she is willing to pay for — a decision that also carries liability. And contractors who don’t precisely follow maps, blueprints and procedures also could face penalties.
QL-B lists some pretty high-tech equipment to locate utilities, but not all utilities can be located with these devices because of their material (e.g., plastic pipes can’t be detected with metal detectors).
QL-A ensures absolute location identification. So why doesn’t everyone take it to this level, especially given the fact that various safe-dig laws require non-destructive excavation when digging within the tolerance zone of a designated utility? The answer lies in a perception problem: QL-A, specifically vacuum excavation, is perceived as expensive.
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