When I last saw results for the state (a few years ago) the two biggest areas in Utah for radon gas test results were Brigham City and Beaver. The results then showed that along the Wasatch front, you had higher test results on the benches - which may be a product of radon gas using the fault line to vent upwards - like using the path of least resistance. But that's just a guess.

One thing, you can vent your house without pursuing mitigation measures by opening windows and doors. If you have little kids to leave doors open or they are constantly running from inside to outside and vice versa, you are going to have lower radon gas test results than similar homes in the area. As your kids grow up and habits change or you become empty nesters, this may impact your radon levels in your house. So you might want to test for radon again, even if you've done it before.