Highway 50 between Riverton and Twin Bridges, 20 to 40 miles east of Placerville in the American River Canyon, sustained substantial damage during last winter's December/January storms. The highway was closed January 1 due to mud slides, flooding and pavement washouts from the American River, reopening 17 days later on January 17 following emergency repairs by three contractors at times working around the clock. That emergency reopening was followed by a massive slide on January 24 4 miles east of Riverton which closed the highway for 28 days. Once again, contractors crews worked seven days a week and, when possible, 24 hours a day, to remove 350,000 cubic yards of slide material from the roadway and the steep mountainside above the road. The highway reopened on February 21.
Once the emergency repairs were done, work got underway on a major improvement project designed to restore the highway to its pre-storm condition and do preventative work. The job, which began July 31, included 39 work locations. Drainage systems were improved by installing new drains, larger pipes and rock lining channels. Slopes were stabilized and rocks placed along slopes between the highway and the river to prevent undercutting the highway during high water. Paving at a number of locations completed the project. At the Mill Creek slide (the name given to the January 24 slide) 4 miles east of Riverton, an additional 140,000 cubic yards of earth has was removed from the mountain side, surface and sub-surface drainage systems installed and erosion control applied to reduce slide potential. The Monday noon through Friday noon detour went into effect September 2.
Additional instruments have been installed in five potential slide areas to enable Caltrans personnel to monitor movement and rainfall (not a part of this contract).
All work on the highway that required traffic control was completed on Friday, October 24. Additional off-highway work continued until November. Although the detour on Alternate 50 (a seasonal Forest Service road) became no longer necessary as of that date, it remained open until covered by snow from winter snows.be necessary.
Through traffic was detoured from noon on Mondays to noon on Fridays from September 2 through October 24. Highway 50 was open with no delays from noon on Mondays to noon on Fridays. The detour was 27 miles longer and took about 40 minutes more travel time.
This Project: Estimated final cost of the project was $11 million. The increase in cost from the original estimate of $9 million was due to work added to the contract at five additional locations and changes in the project in the field to accommodate unknown conditions. It was expected that the contractor would receive incentive pay of $50,000 a day for completing the project ahead of schedule.
Total spent on major Highway 50/Alt. 50 storm restoration in 1997: $25 million
- $6.5 million for emergency opening/repairs in January following flooding
- $4 million for slide removal in Jan./Feb.
- $3 million to repair a slipout and pave Sly Park Road and Mormon Emigrant Trail for use as the Alternate 50 detour
- $11 million for this restoration/prevention project
Frehner Construction Company, Inc., North Las Vegas, Nevada