Tunnel Rehabilitation and Reconnaissance – Dinero Tunnel
Client: Colorado Division of Minerals and Geology as prime to US Bureau of Land Management
Location: Lake County, Colorado, United States

In 2004 MES re-opened the Dinero tunnel in order to support hydrologic evaluation and examine potential sites for a bulkhead seal to stop or retard the acid water drainage entering the Arkansas River. The tunnel initially had a severe collapse at approximately 350 feet from the portal, resulting in a large surface subsidence feature approximately 110 feet above.

The work involved setting up provisions to handle and treat excess water flows, dewatering impounded water from behind the cave-in using a borehole and pump system and recovering the collapsed tunnel by driving spiling and standing steel sets. Work continued in 2005, with the advancement of rehabilitation and exploration of the tunnel an additional 1900 feet.

This work included the recovery and steel setting of several minor collapses, and controlled dewatering of several mine pools, with the treatment of excess flows. MES provided both professional and construction services. Rock mechanics consultation and ground control plans were provided by sub-consultant Dr. John Abel, P.E.