Interstate Bridge

Interstate Bridge
Coordinates	45°36′24″N 122°40′51″W
Carries	Interstate 5
Crosses	Columbia River
Locale	Portland, Oregon to Vancouver, Washington
Maintained by	ODOT, WSDOT
ID number	01377, 07333
Characteristics
Design	Dual truss with vertical lifts
Total length	3,538 (1078 m)
Longest span	531 feet (161.8 m)
Clearance above	15.5 feet (4.72 m)
Clearance below	72 ft closed, 176 ft open
History
Opened	February 14, 1917 (Northbound), 1958 (Southbound)

The Interstate Bridge is a pair of nearly identical steel through truss bridges with a vertical lift that carries Interstate 5 traffic over the Columbia River between Vancouver, Washington and Portland, Oregon.

The bridge was built to replace an overcrowded ferry system operated by Pacific Railway, Light & Power Co. The first bridge was opened on February 14, 1917 at a cost of $1.75 million, which was shared between Clark County and Multnomah County. It was originally a toll bridge costing $.05 per person. In 1958 a $14.5 million upgrade created a southbound span and doubled the capacity of the bridge. The new bridge was built with a "humpback" that provides 72 ft of vertical clearance and minimizes bridge openings. At the time the new bridge was opened, the old one closed to give it the matching humpback. When both bridges were opened in 1960, tolls were reinstated at $.20 for cars, $.40 for light trucks, and $.60 for heavy trucks and buses, before being permanently removed in 1966.

A $3 million upgrade to the lift cables, expansion joints, and a deck repaving was completed in 1990. The diesel generator used to power the lift was replaced in 1995 at a cost of $150,000. In 1999 the bridge was repainted at a cost of $17 million. A $10.8 million electrical upgrade was completed in mid-May of 2005.

The bridge is 3,538 ft long with a main span of 531 ft. The vertical lift provides 176 ft of clearance when opened. The lift takes 10 minutes to open and does so between 10 and 20 times per month. In 2001 the 6 lanes of the bridges carried 120,000 vehicles including 10,000 trucks, operating at capacity for four hours every day.

Currently, many traffic engineers consider the bridge to be obsolete, both due to its age and its limited capacity. The bridge is frequently a bottleneck which impacts both traffic on the freeway, as well as on the river. The Oregon and Washington state departments of transportation are jointly studying how to replace the bridge. The estimated cost for a replacement bridge is $500 million to $1 billion.

A replacment (especially with a non-drawbridge) is complicated by a railroad drawbridge crossing the Columbia a short distance downriver, which constrains the location of the shipping channel; and by approach paths to Portland International Airport in Portland and to Pearson Field Airport in Vancouver, which limit the height of any new structure. Some have proposed replacing the bridge in a different location. There are presently 12 transportation plans that are being studied to improve and expand the Interstate 5 crossing of the Columbia River. In late 2006, 2-4 of these plans will be selected for a final proposal. There is also a long standing debate as to whether or not a new bridge would include MAX light rail.

References

• Wood, Sharon. The Portland Bridge Book. Portland: Oregon Historical Society, 2001. ISBN 0-87595-211-9.

External links

• WSDOT:Interstate Bridge
• Columbia River Crossing: Home page of ODOT/WSDOT project to replace the Interstate Bridge