Reconciling Conflicting Utility Location Data: A Case Study of Submarine Gas Lines in the Providence River

During the course of a major harbor dredging project it was learned that three ten-inch diameter, high-pressure gas lines traversing the Federal Channel may not have been buried to the proper depths. After researching the plans of record on the subject gas line, the USACOE found that the originally permitted burial depths of the pipeline conflicted significantly with two more recent electronic surveys that had been performed. Several more surveys using electronic methods of locating the pipes were attempted; however, because of site constrictions and the pipeline configuration, functionally repeatable results could not be obtained. Because electronic surveys had not produced consistent results, the owner and the USACOE turned to the most reliable method — that of unearthing portions of the pipe, however the Channel depths, the pipe cover and port traffic made this a formidable task. The following case study documents how this task was accomplished.