Option 4, also...what about the sections that are noted as potentially unstable S of Red Bridge?

Convert to pedestrian/bike path. Use appropriate barriers to prevent dumping, tree poaching, etc.

Fixing Blue River road to the tune of $40+million is irresponsible given the low amount of traffic it saw even in its heyday (~1000 cars), this was when the Honeywell site was active at the north end of the area as well, now that is moved I'd guess the number to be even less. Additionally, even if the city was able to find tens of millions of dollars to dump into a low travel road, whose to say the next flood doesn't take out the south section of the road, given that it is noted to have the same geological features as the north.