Optimize Worldwide

Drill Tech was contracted to perform tunnel repair and maintenance work during a powerhouse tunnel outage that included cleaning out rock traps, servicing entry shafts/adits, and repairing rock trap steel/wood structures. The rock traps had accumulated decades of buildup including sands, rocks, sticks, and other debris. This material had to be excavated by hand and hauled several thousand feet to the nearest exit location from the tunnel. The tunnels were accessed via adit and vertical shaft locations where temporary services were set up to provide dewatering, power, lighting, and utilities to the tunnel.  

Concurrently with the tunnel work, Drill Tech’s APEX Rockfall Mitigation also performed rock scaling and fence installation on the access roads to the powerhouse, since Jaybird Canyon’s 1.2 mile, 2-lane switchback road faced the constant risk of rockfall that threatened access to the powerhouse. Drill Tech, via APEX, performed at 3 scaling locations and 2 fence locations. All areas were accessible only by rope teams and winch drilling equipment. The project implemented rockfall fences to meet project intent, with a hybrid approach achieving both the project geometric and technical goals. 

This tunnel was a pedestrian undercrossing designed to connect the Temple’s newly constructed subterranean basement to the Conference Center garage. The site was located in a highly trafficked downtown thoroughfare and required preconstruction preparation to analyze various risks with 3^rd party entities that included utilities, the transportation department, and property owners to mitigate potential ground settlement during tunnel construction. The project required ample communication and collaboration to ensure the expectations were met, including both operational and aesthetic objectives. Drill Tech designed the tunnel shape and support, utilizing open face mechanical excavation through the loose alluvial deposits of cemented sands and cobbles. Waterproofing and shotcrete final liner were installed at the transition between the tunnel and existing facilities from both ends.

This Caltrans project in Monterey County consisted of jacking a concrete box culvert under U.S. 101. The jacking technique eliminated any impacts to the traveling public and surrounding community as the highway remained fully operational.  Drill Tech built the launch slab and box away from the highway, eliminating the need for constructing additional support structures. Because there was only four feet of cover over the box, Drill Tech used a special steel sheet roll-out technique to prevent movement of the highway above. The innovative steel sheet roll-out method ensured successful box installation.

The Range Front Declines were 19-foot-diameter decline connection tunnels for ventilation and material haulage/extraction passages reaching the lower extents and working levels within the existing and active Cortez Hills gold mine.  Excavation was performed in a fully operational mine, necessitating that Drill Tech align with adjacent mining contractors and client operations. This project served as a pilot program and feasibility study for utilizing hardrock roadheaders in mine development by SEM techniques. Drill Tech mined through a mélange of rock conditions ranging from extremely weak to strong, and drill/blast methods were utilized to break through when massive hard rock formations were encountered.  

Drill Tech constructed final CIP concrete structures within the tunnels and caverns for subsequent mining operations, including fuel bays, wash bays, explosive magazines, ore bins, and electrical distribution centers. These structures will serve as permanent mine infrastructure for long-term use and are critical to underground equipment use and maintenance.  Drill Tech optimized the ground support based on insitu materials, only utilizing what was required for long-term stability of underground structures. Several components of the project were completed through concurrent work, such as multiple-heading excavation, progressing the job to finish three months ahead of schedule.  

This tunnel enlargement project for the existing Paulsell Lateral Tunnels 1 and 2 was part of Oakland Irrigation District’s infrastructure maintenance and growth plan. Drill Tech performed the expansion excavation, installed portal walls at the end of each tunnel, and provided access management and maintenance throughout operations. Three existing collapsed ventilation shafts were excavated, cleaned out, and backfilled with lean mix. Acting as the General Contractor, Drill Tech also set up check dams and a diversion system to pump leakage/runoff water around the canal/tunnel work, as it was imperative the low-point tunnels were kept dry and available for work.

Drill Tech performed SWPPP management and maintenance, and remained in compliance to other environmental regulations that required work to halt during rainy or foggy weather. Since the project’s time frame was subjected to a schedule-controlled shutdown, Drill Tech mined the two tunnels at once with separate equipment and mucking operations for the most efficient use of time and resources. Fiber-reinforced shotcrete was placed at either 4″ or 6″ thickness through each tunnel to act as the final liner for the future water tunnel.

This project was part of the Mayo Clinic’s plan for West tower expansion in Phoenix, Arizona. Drill Tech was contracted to build the new tunnel from the proposed excavation under the Mayo Clinic, adjacent to the existing utility room and directly under the active Emergency Room. Tight site conditions and proximity to the hospital’s active operations required a minimal job-site footprint from where Blount performed portal shoring prior to tunnel excavation. SEM roadheader excavation was utilized to construct the 13′ diameter 193′ long tunnel. Ground support consisted of lattice girder and shotcrete. During excavation, Drill Tech was required to excavate adjacent to existing hospital foundation piles and protect them in place. Lastly, Drill Tech installed tunnel water proofing and a reinforced shotcrete final liner. During the project, excessive desert temperatures required night only operations and hospital operations were not impacted by our operations. The project was a great success in the overall hospital expansion project and allowed for future passageways under the hospital for future hospital activities.