Item: The east riverside avalanche accident of 1992: engineering and snow-safety considerations
Title: The east riverside avalanche accident of 1992: engineering and snow-safety considerations
Proceedings: Proceedings of the 1992 International Snow Science Workshop, Breckenridge, Colorado, USA
Authors: Arthur I. Mears, A.1. Mears, P.E., Inc., 222 E. Gothic Ave., Gunnison, CO 81230, U.S.A.
Abstract: A high-intensity snowstorm (>1 m snow and >8cm water in 2 days) produced widespread avalanching in Colorado's northern San Juan Mountains during early March, 1992. While the Colorado Department of Transportation (COOT) was attempting to rescue stranded motorists and close Highway 550 two CDOT employees were caught and buried 40m north of the East Riverside avalanche shed, approximately 8km south of Ouray. One of the employees died. Although Highway 550 is crossed by about 60 avalanche paths, the last six fatalities have occurred at the East Riverside in four separate accidents in 1963, 1970, 1978, and 1992. The State of Colorado is considering two options to reduce avalanche hazard on Highway 550: (a) an approximately 80m-long northward extension of the existing shed, and (b) hiring two full-time forecasters during the November-April period each season. The shed extension would require a front-end, one-time expenditure of approximately $3,000,000, would decrease the hazard in the East Riverside to less than half the present level, but would only reduce the avalanche hazard over the entire Highway by roughly 5%. Assuming a long-term interest rate of 8% and an amortization period of 30 years, the shed would be financed by a constant annual payment of $266,490. Total "mortgage" cost over 30 years, therefore, would be $7,994,700. The forecast program, including salary, overhead, instrumentation, transportation and other expenses, would cost an estimated $100,000 per year and would reduce the hazard over the entire highway by an estimated 50%. If this annual cost also inflates at an 8% rate over 30 years, the total cost would be $11,328,322. The forecast program, therefore would cost 1.42 times the shed cost over 30 years, but would provide roughly 10 times the hazard reduction.
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Keywords: rescue, accident, forecast program, hazard reducation
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