S.H. 133 Paonia Reservoir Rockfall Mitigation
Somerset, Colo.
Best Project

Owner Colorado Dept. of Transportation
Lead Design CDOT
Blasting & Drilling Blackwing Blasting Inc.
Owner’s Rep/Inspector HDR Engineering Inc.
General Contractor Kissner General Contractors Inc.

A section of State Highway 133 at the base of the West Elk Mountains near the Paonia Dam in western Colorado is known for its daily rockfalls. Crews installed a new mesh system and soil-nail wall to make the highway safer for drivers. The rockfall mitigation included 500 hours of rock scaling, 4,000 cu yd of trim blasting, 11,000 linear ft of drilling and anchor installation and placement of 79,000 sq ft of anchored mesh along a 1.5-mile stretch of highway.

Kissner General Contractors Inc. (KGCI) also installed 800 linear ft of 8-in.-thick shotcrete soil-nail wall that averaged 18 ft tall. The wall construction required 7,710 linear ft of drilling and anchor installation, 33,000 sq ft of wire mesh and 610 cu yd of shotcrete. KGCI excavated 15,000 cu yd of material from the highway shoulder to ensure proper placement of the shotcrete wall and allow easier access for the cranes and man-lifts. Crews constructed a bar ditch and a safe-catch area for falling rocks that was up to 60 ft wide in some place.

To complete drilling for the mesh, crews used two cranes and a 180-ft man-lift with drills mounted in each of the baskets. Drill holes were spaced in a 10-ft diamond pattern at 12 to 15 ft deep. Anchors consisted of Grade 75, No. 8, epoxy-coated bar, placed in each hole and solidly grouted. Crews grouted every three days on average and tested the grout each day. Pull tests were also done on 5% of all the anchors installed to ensure they met the required design load of 36 kips.

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