The proposed new Interstate 5 Bridge must meet several contradictory mandated design criteria. High enough to let river traffic pass, not too high that it impedes on two airports, low enough that ground vehicles can access it reasonably. Ideally this could all be accomplished without the need for an opening span. As first proposed, the height of the bridge would allow for almost all of the river traffic with the exception of several rare passages per year.
Can the bridge be designed to a height that would allow all but very rare, exceptionally tall river traffic, but with an opening span? This height would automatically limit the opening to very few occasions per year, but there could be a further stipulation that all bridge openings would have to be scheduled in advance and limited to the hours between midnight and 5 a.m.
I can't imagine the cost would be much higher than constructing the bridge to the maximum height needed for all river traffic. The disruptions would be minimal. This would require a little give on the part of all the affected parties, but it seems a logical way out of what seems now to be an unsolvable dilemma.