Under an Overpass
There are tons of overpasses in salt lake city and every time I drive by or under one I am astounded by the wasted space. So many things could be built under them to make them great assets to the community. In Canada they have built parks under the overpasses, many countries in Europe turn them into pieces of art, other states like Oregon have turned the dead space into basketball and skateboarding parks. In China and Mexico they are turning these places into business and housing. Idaho uses theirs for a farmers market. I would love to see this dead space all around the city turned into something great and useful. My own neighborhood (Jordan Meadows) has a few that I would love to see transformed and if the city doesn't do something about this issue then I plan on starting a crowd funding campaign to fix the problem myself. I don't see why I have to look at something so ugly when it could be a safe beautiful place.
Each overpass has different owners. It is likely you will need to contact UDOT for anything relating to I-15. I'm sorry but I am not sure of the best way to approach them or who to go to for permission. Likely the best place to start would be their property management group.
Do you know who I would contact in the city government to get permission to renovate the space under the overpasses? Which department has control of these spaces? I thought long and hard about what I could do and I believe if I can get a favorable response from the city government it would be possible to start a non-profit dedicated to turning these space into community gatherings and pieces of art. We could then host a KickStarter campaign to raise the funds. But, first I would like to see if the government would even grant us permission for such a thing.
This summer SLC will begin improving the area under the 900 South freeway pass, with improvements to the bike track there. Two years ago we did a community build on the pump track and we are looking to build on that. the The bike park will serve as an example of what you are looking to do. I think a crowd funding campaign is a good place to start it would help inform policy makers of the potential and acknowledges the community support for the idea.