In November 2023, DA Smith was commissioned by HDR, Inc. to drill an exploration horizontal core hole adjacent to the alignment of the historic Nelson Tunnel in the Creede Mining District of central Colorado. Drilling was being conducted for the purpose of geological characterization as part of the U.S. Environmental Protection Agency’s Nelson Tunnel/Commodore Waste Rock Pile Superfund site project.
Although the hole was collared on surface, the horizontal alignment of the hole required using DA Smith's Boart Longyear LM90 underground electric-hydraulic diamond core rig. The expectation for significant groundwater required the installation of a high-pressure blowout preventer (BOP) at the collar to regulate discharge. Outflows were captured and diverted 400 feet downstream to a dedicated detention pond.
A stiffened H-size coring setup was used to minimize hole deviation. Routine downhole deviation surveys conducted by DA Smith confirmed that the hole trajectory remained parallel to the tunnel alignment.
Logistical challenges included operating in heavy snow and sub-zero temperatures at the remote mountain site during winter. The hole was completed at 1,042 feet depth with excellent core recovery.