The Big 5 Tunnel is a drainage and haul tunnel for a network of underground mines near Ward, Colorado.
Portal with drainage flows.
The portal exits at the Captain Jack Mill site. The tunnel was examined to evaluate the feasibility of installing a bulkhead to control mine drainage flows into Left Hand Creek. It was determined that prior to constructing any bulkhead, the ground support in the area would have to be improved for safety and future stability.
Overview of ground support rehabilitation.
Deere & Ault Consultants, Inc. investigated the tunnel from the portal, past a collapse and earlier bypass, to an existing collapse around 860 feet in. The investigation included mapping of joints and shears, classifying the ground conditions, and documenting the condition of the existing support.
Deere & Ault then designed new ground support consisting of rock bolts, mine straps, and shotcrete. During construction, Deere & Ault reviewed contractor submittals and the contractor’s support change in one area from shotcrete to steel sets.
Clients: Walsh Environmental Scientist and Engineers LLC,
Environmental Restoration Inc., and
Environmental Protection Agency