Rigonomics: With Low Rates, HDD Rig Selection Is Critical

By Jeff Griffin, Senior Editor | June 2010 Vol. 65 No. 6

A common practice, said Crumpton, is to “leap frog” two machines, completing the pilot hole with the small machine, moving it off to the next bore down the line, and bringing a larger unit for the reaming and pullback.

“The leap-frog method can save time and money if done correctly for particular formation types.” Crumpton explained. “It is practical in many soft rock and soil formations. Other factors to consider in the leap-frog process are the length of the bore, the rock type and the hardness.”

A subcontractor is another possible solution. “If the job consists of only one bore,” Crumpton said, “using only one rig that can complete the bore is the best method. On most rock bores, a large rig has to do the complete bore.”

InRock, (713) 690-5600, www.inrock.com

Editor’s Note: In the September issue of Underground Construction, Rigonomics will cover drilling the pilot hole.