AN ASSESSMENT OF UTILITIES LOCATING PRACTICES AND EXCAVATION DAMAGE

Excavation damage to underground utilities is caused by three main root causes, namely: One-call notifications were not made or not sufficient, unsuccessful locating practices, and excavation practices not sufficient. This paper investigates the root-causes of excavation damage and the effect of various site characteristics and locating practices on the success of locating belowground utilities. Excavation damage incidents were reviewed from the National Transportation Safety Board (NTSB) pipeline incident reports and Pipeline and Hazardous Materials Safety Administration (PHMSA) records of natural gas distribution (GD), gas transmission (GT), and hazardous liquid (HL) lines from 1970 to 2019. These records were stored in an SQL database and a web-based data management program was developed for displaying the distributions and relationships between the root causes and incidents' parameters. The incidents' data analysis was performed using a Bayesian Network (BN) approach for the evaluation of the probabilities of locating failures under variable parameters. BN provides the flexibility of updating the probabilities when performing risk and sensitivity analysis under various conditions. The means by which BN is processed enables performing the sensitivity analysis quantitatively as well as ranking the significance of the risk factors. The paper presents the relationships and causality of the parameters affecting the performance of Electromagnetic (EM) and Ground Penetrating Radar (GPR) Locators. A parametrical study was performed to evaluate the effect of site conditions (such as soil type and moisture), pipe attributes (material, size, and depth), and locating practices (such as equipment type and frequency) on the probability of a successful locating. The results demonstrate the significance of the pipe diameter to depth ratio and device frequency on the probability of detection.