Water is the biggest problem. Both you and your dog should drink lots of water before and during the hike. Get a doggy back pack and let Fido carry his own water. The first sign of heat exhaustion is uncontrollable panting. If you suspect that your dog is suffering from heat exhaustion wet down his coat with all the water you can spare and get him to a vet as soon as possible.
Rattlesnakes are plentiful in the foothills around Salt Lake City.
If your dog is on a leash, just being observant and careful will probably be sufficient, but if you allow your dog to roam, it would be a good idea to have him snake proofed. Since your dog will catch the scent of a rattlesnake before you will see it, it could be an advantage for you, too. Giardia is a waterborne parasite which causes severe diarrhea, vomiting, and weight loss. Dogs may be more resistant to Giardia than humans, and it is treatable with several common drugs. Since it can also be picked up in kennels, and even from puddles, trying to keep your dog from drinking from mountain streams might be more trouble than it is worth.