The Isthmus Slough Bridge is significant as a good example of the bascule bridge type. This bridge is unique within the Oregon context at it is the only known bascule structure that utilizes a block and tackle lifting mechanism, as opposed to the more common motorized lifting mechanism. The lack of motorized technology distinguishes this structure within Oregon's context of moveable bridges. The Isthmus Slough Bridge is also significant as a late example of the bascule type within Oregon, as it is only one of three bascule spans built after WWII.
(HAER OR-144 - Isthmus Slough Bridge)
Length of largest span: 85.0 ft.
Total length: 686.1 ft.
Deck width: 24.0 ft.
Vertical clearance above deck: 14.1 ft.
Eligible for the National Register of Historic Places
Approximate latitude, longitude
+43.30083, -124.20861(decimal degrees) 43°18'03" N, 124°12'31" W (degrees°minutes'seconds")
Approximate UTM coordinates
USGS topographic map
OR 02300A (Oregon Dept. of Transportation structure number)
BH 29928 (Bridgehunter.com ID)
Inspection (as of 08/2005)
Deck condition rating: Good(7 out of 9) Superstructure condition rating: Serious(3 out of 9) Substructure condition rating: Poor(4 out of 9) Appraisal: Structurally deficient
Sufficiency rating: 13.5 (out of 100)
Average daily traffic (as of 2004)
April 20, 2009: Posted HAER photos
December 4, 2008: Updated by Michael Goff: Updated Status
Mike Goff - michael [dot] goff [at] hotmail [dot] com