The Engineer developed four prefabricated self weathering steel truss bridge alternates at two locations that addressed these concerns in various ways.
The two alternates at the north location gave less central access to the bike trail and neighborhood, and the spans were long, but they claimed more direct access to a nearby mall. The structures were located away from intersecting ditches where dredging was less of an issue.
The Alternate 3 - 130 ft long by 6.75 ft tall truss was located so as to preserve the maintenance road along both sides of the creek.
The Alternate 4 - 154 ft long by 7.75 ft tall truss had a high clearance that allowed the maintenance road to pass beneath preserving roads along both sides of the creek. Dredging could also be performed under the structures. Due to its height this alternate required access stairs, bike and ADA ramps. POITRA removed a large part of the trail access road and routed it under the new structure. This required restoring the newly exposed creek channel in the photograph.
The past bridge design experience of POITRA principals made the transition from design plan to the finished structures that appear in the visualization seamless and efficient. POITRA illustrated each alternate using combined 3D rendering and traditional digital painting techniques.
To add the truss bridges and abutment walls including the ramps and stairs for Alternate 4, POITRA modelers built accurate, properly cambered and detailed 3D truss models with abutments which were then camera matched to the photograph. The models were then appropriately lighted, rendered and composited with the photograph to create the final photo realistic simulation of the proposed conditions for each alternate.
The simulations were used in meetings between VTA, PGE, the Water District and the neighborhood.