Outer Banks and the importance of locating underground utilities

Hatteras and Ocracoke Islands in North Carolina’s Outer Banks are currently under a mandatory evacuation order. Construction crews working on the Bonner Bridge accidentally drove a steel casing into an underground power cable. At this time it is not clear what led the contractor to make the mistake and whether the location of the underground power cable was clearly indicated on the construction plans. What is clear is that the expected one to two-week mandatory evacuation is going to cost the Outer Banks a lot of money in the midst of peak summer vacation. Design professionals have to pay extra attention to the location of underground utilities during the design phase of their projects.

Gone are the days when a simple note on the construction plans stating “the contractor should locate all underground utilities before starting excavation” will suffice for a construction project. In the past, there was little effort made to locate underground utilities during the design phase beyond picking up visible utility features during a topographic survey. With our aging infrastructure, it is clear that professionals did not accurately document utilities when they were installed decades ago, and even if they did, the records are not readily available. More thought has to be given to how the exact location of underground utilities is shown on plans so that contractors have more reliable information.

The American Society of Civil Engineers (ASCE) has published ASCE 38, Standard Guideline for the Collection and Depiction of Existing Subsurface Utility Data. The guideline outlines specific steps for an engineer or surveyor to take that will result in increasingly better utility mapping. Using the reference, the design professional and owner can decide how much information will be included in the construction drawings and decide on the recommended scope of services and procedures for the identification and mapping of existing utilities. By taking these proactive steps with the owner, the design professional can reduce the likelihood of a similar incident occurring on their project.