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SR 155 - South of Electric City - Rock Slopes Scaling - Complete May 2011

Complete May 2, 2011
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Four slopes near Steamboat Rock State Park in upper Grant Count were stabilized:
Slope 1: MP 18.57 to MP 18.69,
Slope 2: MP 19.60 to MP 19.68,
Slope 3: MP 19.68 to MP 19.85,
Slope 4: MP 19.94 to MP 20.04.

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This is the detour that was in effect for eight days as the project began in April.

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A January 2009 rockfall prompted this project.

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 Slope 4, MP 19-20


Complete May 2011

  • Construction began on Saturday, April 2 with a full closure of the highway and a detour through Sunday, April 10. 
  • Following the full closure, there was single lane, flagger controlled traffic during daylight hours, Monday through Friday until the work was complete on May 2, 2011.

This Risk Reduction Program project stabilized four rock slopes 5 miles South of Electric City, near the entrance to Steamboat Rock State Park and Northrup Canyon.

Why is WSDOT stabilizing these slopes?
This project will reduce rockfall onto SR 155 along Banks Lake.  

These slopes were identified for stabilization under the WSDOT Unstable Slope Management Program. The slopes were evaluated, rated and analyzed for cost vs. benefit in 2004 and failed to qualify for funding.

In February 2009, the Risk Reduction Scaling Program received additional funding for slopes to provide partial mitigation to reduce the risk of rockfall.  This came at a good time, as there was a significant rockfall event on the SR 155 slopes in January 2009.  Additionally, when the slopes were studied closer, WSDOT engineers found tension cracks on the slopes which Maintenance crews believe to be widening over time.  Since Geotech engineers agreed that the cracks were widening, and the slopes were generally becoming more unstable, the 4 slopes were programmed for funding with the additional scaling funds. 

To restore the stability of these slopes we:

  • Scaled loose rock by hand
  • Mechanically removed larger rocks
  • Removed other potentially hazardous debris

The End Result
The risk of encountering falling rocks on SR 155 is significantly reduced. 

Project Benefits

  • Reduced risk of rockfall-caused collisions
  • Reduced maintenance clean up costs
  • Fewer pavement repairs

What is the project timeline?
Construction begins April 2 and was complete May 2, 2011.

We planned our work around local events and festivals to reduce traveller and community economic impacts.  The high traffic impact work for this project was completed by May, when the busy season for Steamboat Rock State Park and fishing on Banks Lake began.

Financial Information

Financial Data for PIN 215500E
Funding Source Amount ($ in thousands)
2003 Gas Tax (Nickel Funding) $0
2005 Gas Tax (TPA) $0
Pre-Existing Funds (PEF) $804
CWA $0
Total $804

Project signage will reflect the cost of construction engineering, project bid award and sales tax.

This project was advertised for private contractor bids Dec. 6, 2010. Ten qualified bids were opened Jan. 6, 2011. On Jan. 10, Contract #8064 was awarded to the low bidder, KRCI LLC for $631,206.73, 28% below the engineering estimate.

This project is funded through the following sources:

  • Pre-Existing Gas Tax - $1.15 million
  • Total funding from all sources - $1.15 million

How can I get more information?
Bob Romine
Project Engineer
WSDOT North Central Region Project Office
PO Box 98
Wenatchee, WA  98807
Phone: 509-667-2880, or toll free 1-888-461-8816

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