From: Tom Warren, PE, Warren Engineers, PLLC
Regarding: Design and Cost Analysis for Proposed Elevated Structure Concept for Sound Transit Rail
At the request of the DDDG, we have developed a preliminary alternative design concept for the Sound Transit Sounder Commuter Rail extension through the Dome District. The elevated structure (bridge) is based on current state-of-the-art technology used by the railroads. Currently, the alternative has been called “post and beam”, but is more accurately termed “bridge” or “flyover” in standard railroad nomenclature. The following photograph of the Kansas City Flyover (1) provides a visual representation of the basic bridge structure.
For our analysis, we assumed a total length of 1450’, consisting of 1350’ of bridge structure with supports at 32’ average intervals, and a separate bridge of 100’ span over Pacific Avenue. Our cost estimate for the 1350’ section is $13,683,000 ($10,140 per foot) and $4,500,000 for the Pacific Avenue Bridge for a total cost of $18,183,000 for the structures. This estimate is for the structures only, and does not consider design, permitting, utility relocation and installation, road crossing at grade work, traffic control, surveying, excavation of Pacific Avenue, nor inspection.
The basic design is the same as that used by Burlington Northern (BNSF) and Union Pacific (UP) railroads to build elevated structures or bridges around the continental United States. BNSF and UP have jointly developed these design standards. Canadian National uses the same methodology in Canada.
Here’s a link to the full report, cost estimates, pictures and drawings:
Full Report on Design and Cost Analysis