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West CA-120 To South I-5 Ramp Bridge

Mossdale Highway Bridge

West CA-120 To South I-5 Ramp Bridge

Primary Photographer(s): Nathan Holth

Bridge Documented: April 5, 2013

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Key Facts

Facility Carried / Feature Intersected
West CA-120 To South I-5 Ramp Over San Joaquin River
Mossdale: San Joaquin County, California: United States
Structure Type
Metal Rivet-Connected Warren Through Truss, Movable: Single Leaf Bascule (Fixed Trunnion) and Approach Spans: Metal Continuous 6 Panel Rivet-Connected Warren Pony Truss, Fixed
Construction Date and Builder / Engineer
1948 By Builder/Contractor: Judson Pacific Murphy Company

Technical Facts

Rehabilitation Date
Not Available or Not Applicable
Main Span Length
130 Feet (39.62 Meters)
Structure Length
583 Feet (177.7 Meters)
Roadway Width
27 Feet (8.23 Meters)
1 Main Span(s) and 4 Approach Span(s)
NBI Number
29 0016F

Historic Significance Rating (HSR)

Bridge Documentation

View Archived National Bridge Inventory Report - Has Additional Details and Evaluation

While not an early example of the technology, this bridge has some unusual aspects that make it noteworthy. The bridge is a common type of bascule, the fixed trunnion, but it is unusual because it has an overhead counterweight and trunnion. With fixed trunnion bascules, most commonly the counterweight was located below the deck in a counterweight pit, and the trunnion would also be located below the deck. With the trunnion clearly visible above the roadway, and the massive counterweight hard to ignore, the bridge is a very visual display how a fixed trunnion bascule works, even though it no longer operates for boats. The approach pony truss spans of this bridge are also noteworthy because they are continuous. The concrete counterweight was carefully designed to visually merge with the trusses rather that sticking out like on many bascule bridges. To help reduce the size of the counterweight, heavy magnetite aggregate was used in the concrete to maximize the weight.

This area has a long history of bridge crossings. In 1869 the Transcontinental Railroad was extended from Sacramento to Oakland, passing through here.


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