Examining and Mitigating the Common Causes of HDD Failures
Prepared for the North American Society for Trenchless Technology (NASTT) 2014 No-Dig Show by Blake Peters, PE, McKim & Creed; Jeffrey S. Lowe, PE, McKim & Creed; Seton Katz, PE, Sarasota County Capital Management Services
At 3:00 p.m. on a Friday afternoon, during the product pipe pullback of a horizontal directional drill, a hydro-fracture occurred within inches of a federal highway. This caused the contractor’s personnel to cancel their weekend plans, scramble to bring in maintenance-of-traffic devices, notify the state highway manager and deal with a myriad of other inconveniences and potential financial losses. Utility staff attempted to understand what had gone wrong, which revealed a hard truth. We didn’t really know what had gone wrong. This left us feeling very lucky the hydro-fracture hadn’t actually washed out the highway, but also very exposed to the possibility of a repeat occurrence.
Over the last eight years, horizontal directional drill (HDD) has become increasingly popular on County Utility projects. That time has been marked by an increase in the number, length and complexity of horizontal directional drills. Those projects have experienced many successes; however, there have also been many failures, such as lost drill tools, hydro-fracture, failed drill stems, and other abnormal events. Looking back at a wide variety of HDD projects, we found many of the failures were preceded by signs of impending problems. This made us wonder: Would it be possible to identify those signs in advance of an impending failure and, if so, intervene and mitigate the losses?
This paper will identify commonalities and root causes of many directional drill failures, and will share strategies for preparing, recognizing and addressing those issues so that losses and failures can be reduced.