The existing L-400 Bridge is a suspension bridge consists of one continuous 36-inch pipe supported by two V-Frame towers, one on the North side of the canal and one on the South side of the canal. The pipe carries natural gas at approximately 900 psi. The pipe is held in place with cables and suspenders. The bridge has a main span of 246 feet with a main cable length of 250 feet.

Each cable consists of a 1.75-inch diameter wire rope and is continuous between the two towers. The cable provides support to the pipe via suspenders which consist of 0.5-inch diameter 19-wire galvanized bridge strands. The suspenders are connected to the cables by looping them over conventional cast steel cable bands that are clamped to the cables and held in place with friction. The suspenders are connected to the steel T shaped saddles that cradled the pipe. The pipe bears directly on the tops of these saddles.

The tower is a V-shaped transverse frame and consists of steel pipes of various diameters. The cables are attached to the tower tops with pinned connections, so the cables act as tower guys. The towers are anchored to the ground by a pair of cross cables. The anchorage is of the gravity type and consists of a pier cap on top of tripod of three concrete shafts.

An evaluation of the bridge has been conducted by OPAC for PG&E under Golder Associates. The evaluation consisted of development of computer model of the bridge for use in structural analysis, evaluation of response using the results from the analysis, and determination of structural adequacy of key bridge components. The evaluation is supported by visual assessment and survey of the bridge. The evaluation findings are used to retrofit the bridge. OPAC also performed the retrofit design.