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New Tool Helps Colorado Contractor Tackle Tough Ground Conditions
After taking into account the ground conditions and precision placement, NCC decided to place the bore pit in between the highway and railway and complete two bores – one 340-foot bore under the highway and then turned the auger boring machine around and complete a second 340-foot bore under the railway.
“We were concerned that the ground conditions may limit our ability to effectively complete a 700-foot bore and we had a slight deflection into the receiving pit on the far side of the railway,” says Zadel. “We figured the chances of losing material in front of the head were high and that could potentially affect the structure of the highway; plus, hitting that mark in the receiving pit would be easier with a shorter bore.”
Due to the ground conditions and precision needed to hit the receiving pits, Zadel decided to try a new steering head. He recently received a mailing touting the On-Target steering head from McLaughlin. The new steering head allows contractors to not only control horizontal on-grade (up and down) changes, but also allows for lateral (left to right) direction changes. The system provides contractors with more control of the auger boring steering head leading to higher accuracy for difficult on-grade bores.
The cutting path -- grade and lateral movement -- of the steering head is controlled by hydraulic actuated panels that open and close to keep the head on the intended path. A control station features a hydraulic power pack to control the movement of the steering head, and a built-in water level helps monitor grade throughout the bore. Two halogen lights in the control station indicate lateral (left and right) steering head movements.
“We felt the On-Target steering head offered us the steering capabilities we needed to keep the material tight in the front of the steering head, so we wouldn’t lose the material as we were boring,” says Zadel. “We had to shoot in an area where, if we didn’t make our points on the both sides, we’d be on private property within 20 feet of a house or into existing utilities, and that would have made it quite difficult to try to excavate and install the water main. We really had a two-foot-square window to hit, so a conventional steering head wasn’t an option.”
The bore pit was placed in between the highway and railway at a depth of 16 feet to provide the necessary cover requirements. The auger boring machine was placed in the pit and Zadel and his crew began working on the 340-foot shot heading west that passed under the highway while pushing the 36-inch casing into place.