Underground

Location

South Fork and Pagosa Springs, CO

Owner

Colorado DoT

Contractor

Kiewit Western Co.

Value

$13.5 million

Completion

January 2003

Located at an elevation of 10,850 ft., the $13.5 million Wolf Creek Upper Narrows project involved excavating a tunnel to bypass the steep "upper narrows" curve between South Fork and Pagosa Springs, Colorado. It is referred to as the "upper narrows" due to the tight, steep and curvy roadway characteristics.

Part of the State Hwy. 160 eight mi. widening and rehabilitation, the 27-month Wolf Creek project involved mining a 901-ft.-long by 47-ft.-wide by 28-ft.-tall two-lane tunnel through welded volcanic tuff just 35-ft. south of the existing roadway. In addition to tunnel construction, two 105-ft.-long by 10-ft.-tall by 8-ft.-wide pedestrian footpaths were designed for emergency egress. Completed in January 2003 by Kiewit Western Co., a subsidiary of Kiewit Corporation, the majority of construction was completed on a 6% grade at 9,000 ft. altitude.

The scope of work involved drilling, blasting and excavating two wedge-shaped 1,200-ft.-long surface rock cuts to provide access to the tunnel's east and west portals, as well as a 300-ft.-long rock cut just north of the highway to realign the downhill curve leading into the east portal. Crews drilled, shot and excavated 182,000 cu. yd. of rock; shot 40,000 cu. yd. of rock; installed more than 26,100 ft. of 10- and 12-ft.-long resin bolts and 14,000 ft. of rock bolts; placed 22,000 ft. of wick drains; and applied 4,000 cu. yd. of shotcrete.

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