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SR 20 - Sharpe's Corner Interchange - Design Options

January 2008

Design options
These are the preliminary design options which we displayed at our November 2007 open house. In January 2008, we held a value engineering study, which concluded that a modified roundabout is the best option. 

The options below do not include all the features or exact measurements that the final finished design will provide.


Picture of Texas T

Option 1: Texas T (pdf 396 kb)
Estimated cost: $46 million to $51 million

Remove left turn lanes and build elevated ramps over the Sharpe’s Corner intersection. And, modify the Fidalgo Bay Road intersection on SR 20 Spur.  

design visual (pdf 136 kb).
                   
    Strengths

  • Improves safety,
  • Removes traffic signal for eastbound traffic,
  • Reduces intersection delay,
  • Expected to operate efficiently through 2032.

    Weaknesses

  • Significantly builds into surrounding high-quality wetlands,
  • Changes access to local businesses,
  • Will have to buy the most amount of property from surrounding properties in order to build,
  • Elevated bridge/ramp changes visual appeal of surrounding area,
  • Will take a significant amount of time to build, causing delays for drivers,
  • Cost exceeds current budget.

Picture of Texas T By Pass

Option 2: Texas T Bypass (pdf 391 kb)
Estimated cost: $34 million to $39 million

Close the existing Sharpe’s Corner intersection and build a new intersection approximately 480 feet to the east. Remove left turn lanes and build elevated ramps over the intersection. And, modify the Fidalgo Bay Road intersection on SR 20 Spur.  

    Strengths

  • Improves safety,
  • Provides business access on the converted south leg to the extension of Fidalgo Bay Road,
  • Does not build as much into surrounding wetlands as option 1,
  • Reduces delay for drivers,
  • Expected to operate efficiently through 2032.

    Weaknesses

  • Dramatically changes access to local properties and businesses,
  • Will have to buy a significant amount of property from surrounding area to build,
  • Elevated bridge/ramp changes visual appeal of surrounding area,
  • Will take a significant amount of time to build, causing delays for drivers,
  • Cost exceeds current budget.

Picture of Eastbound Flyover

Option 3: Eastbound Flyover (pdf 383 kb) 
Estimated cost: $35 million to $39 million

Build an elevated ramp over the Sharpe’s Corner intersection for eastbound SR 20 Spur drivers. And, modify the Fidalgo Bay Road intersection on SR 20 Spur.  
   
    Strengths

  • Improves safety,
  • Eastbound SR 20 Spur drivers bypass the intersection with a ramp, relieving congestion and reducing delays for all drivers,
  • Little change for businesses along SR 20, heading south towards Whidbey Island,
  • Requires the least amount of property to build when compared to options 1, 2 and 4,
  • Expected to operate efficiently through 2032.

    Weaknesses

  • Builds into surrounding high-quality wetlands,
  • Elevated bridge/ramp changes visual appeal of surrounding area,
  • Will take a significant amount of time to build, causing delays for drivers,
  • Cost exceeds current budget.

Picture of West to South Flyover

Option 4West to South Flyover (pdf 386 kb)
Estimated cost: $34 million to $40 million

Build an elevated ramp over the Sharpe’s Corner intersection for westbound drivers turning left at the intersection. And, modify the Fidalgo Bay Road intersection on SR 20 Spur. 

    Strengths

  • Improves safety,
  • Westbound SR 20 drivers turning left towards Whidbey Island bypass the intersection with a ramp, relieving congestion and reducing delays for all drivers,
  • Slightly builds into surrounding wetlands,
  • Expected to operate efficiently through 2042.

    Weaknesses

  • Dramatically changes property/access for southbound businesses,
  • Will have to buy a significant amount of property from surrounding area to build, 
  • Elevated bridge/ramp changes visual appeal of surrounding area,
  • Will take a significant amount of time to build, causing delays for drivers,
  • Cost exceeds current budget. 

Picture of roundabout

Option 5: Roundabout (pdf 362 kb)
Estimated cost: $11 million to $13 million

Build a two-lane roundabout at the Sharpe’s Corner intersection. And, modify the Fidalgo Bay Road intersection on SR 20 Spur.  

    Strengths

  • Improves safety,
  • Significantly reduces injury and fatal collisions,
  • Minor changes to businesses south on SR 20,
  • Fewer and shorter delays for drivers than a signal,
  • Fewer and shorter delays during construction,
  • Estimated cost within current budget,
  • Expected to operate efficiently through 2036.

    Weaknesses

  • Traffic forced to slow down through intersection,
  • Drivers may be unfamiliar with roundabouts,
  • Moderate changes to businesses at the corner of the intersection

Picture of Continuous Flow Intersection

Option 6: Continuous Flow Intersection (pdf 367 kb)
Estimated cost: $20 million to $23 million 

Modify the existing intersection so that westbound drivers turning left at the Sharpe’s Corner turn before they get to the signal. A new signal would be installed east of the existing signal to help drivers turn left. The signals will be timed so drivers only stop once. And, modify the Fidalgo Bay Road intersection on SR 20 Spur.

Watch streaming video of a Continuous Flow Intersection courtesy of the ABMB Engineering Web site.

    Strengths

  • Improves safety,
  • Minimally builds into wetlands,
  • Minor changes to businesses on south side of intersection, compared to options 1 through 4,
  • Expected to operate efficiently through 2041.

    Weaknesses

  • Significant changes to auto dealer businesses,
  • Drivers may not be familiar with this design. It has never been built in Washington before. 

Funding
The state has earmarked $21.9 million for improvements, and construction is scheduled to begin in 2011.

When this project was funded by the Legislature in 2005, the intent was to transform the intersection into an interchange with bridges and ramps. However, construction and real estate costs have risen dramatically since then, causing the cost of a bridge or ramp to surpass the budget.

In 2006, the Legislature denied a WSDOT request for more money to build a bridge or ramp. Since then, engineers have developed additional designs that improve the intersection and relieve congestion, while staying within the budget.

The two options that fit within the budget are a roundabout and a continuous flow intersection. If another option must be selected, the state would have to grant more money.