Directed Technologies Drilling recently completed a river crossing and pullback of 16″ pipeline in the Midwest. The pipeline was necessary to replace a hazardous line that was trenched across the river years ago, and is now exposed to open air or the river flow, depending on the water stage. A careful view of the aerial photo below, shows the original pipeline is visible in/on the river bed.
The local geology consisted of glacial outwash (sand and gravel) overlying a hard sandstone bedrock. While drilling, the bore quickly passed from outwash sands into the bedrock on the entry curve. Then, at a position approximately 25′ beneath the river, the bore passed into broken bedrock and cobble, and finally back into sand on the exit curve. The variable geology required multiple trips into and out of the bore to change drill tooling, as well as careful drilling technique to minimize risk of inadvertent returns to the river.
The bore was completed safely, without loss of drilling mud to the environment, and on time.