Client: Cominco Engineering Services, Ltd.
Owner: Cominco Alaska, Inc. (now TeckCominco)
Cost of Work: $45 million

PND was prime engineering consultant for design of this major access road in northwestern Alaska, approximately 80 miles north of Kotzebue, extending 54 miles from the Chukchi Sea to the Red Dog Mine, one of the largest and richest lead/zinc mines in the world.

PND performed preliminary geotechnical exploration; located borrow pits; evaluated stream and river hydrology; assisted with permit filing; and directed area terrain mapping, performed using photogrammetric techniques. Based on acquired data, PND designed a road alignment that maintained close proximity to borrow sources, minimized the number and size of stream crossings required, and provided the best foundation.

PND directed field surveys of the alignment, temporary roads to borrow pits, and the borrow pits themselves, and concurrently managed production of plan and profile drawings for alignment. An in-depth final site assessment, including geotechnical investigation, hydrology studies, vegetation analysis and slope stability studies, and soil thaw-depth studies, was completed. More than 180 test holes were drilled at major stream crossings, material sources, and road centerline. Hydrologic studies included field surveys of stream cross sections, runoff and snow drift depth measurements, and determination of flood flow characteristics.

Preliminary and final design for the roadway, turnouts, and all bridges and culverts was provided. To accommodate 1,600-ton mining modules and large ore carriers, the road has a maximum 4% grade and minimum 600-foot curve radii. It was set directly on undisturbed tundra cover, to insulate and protect underlying frozen soils. A minimum of 4 feet of gravel cover ensured summer thaw would not reach ice-rich soils below the vegetative mat. High-strength filter fabric was placed under the road embankment to resist potential slope failures under heavy loads. Approximately 1.6 million square yards of filter fabric were utilized - one of the largest applications in the world.

In all, 10 bridges traverse major drainages. The standardized 40-foot bridges, with steel piles, steel superstructure and precast concrete deck, allowed rapid construction. Pile installation incorporated techniques to accommodate marginally frozen soil and weathered bedrock. Seven major culvert batteries and 500 minor culverts totalling over 7 miles were designed. For flexibility, project specifications were written to make culvert positioning acceptable either during road placement, or by breaching the road after pad construction.