Koehler Tunnel

Koehler Tunnel

Near Ouray, Colorado

Deere & Ault Consultants, Inc. teamed with Shannon & Wilson to provide engineering services for this abandoned mine adit situated just south of Red Mountain Pass approximately 13 miles south of Ouray, Colorado. Acidic mine waters were seeping around the existing bulkhead approximately 300 feet inside the tunnel. Our team was tasked by the Colorado Division of Reclamation, Mining and Safety (CDRMS) to develop a tunnel drilling and grouting plan to seal water pathways in the bedrock that allowed water from the mine pool to seep around the bulkhead.

Bulkhead overview of the Koehler Tunnel.

Our work included analyzing available joint orientation data and site topographic information to evaluate overburden pressures and rock mass stability during grouting. Joint orientation information was used to determine the depth, spacing, and alignment of grout holes. Joint orientations and overburden pressures were used to develop allowable pressures for grouting. We researched available grout materials and evaluated their suitability for use in a highly acidic environment, as well as their ability to perform under the water pressures anticipated at the site.

Portal into the Koehler Tunnel.

We developed a drilling program and grouting work plan to reduce seepage. Due to the low flows and tight joints, the team approached the project with the Grouting Intensity Number (GIN) method which uses a single stable mix and a function of volume and pressure for stoppage criteria. The team developed plans and specifications for the drill hole layout, lengths, pressures, and materials.

Client:  Colorado Division of Reclamation, Mining & Safety, Bruce Stover (303) 866-3567

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