Yes I do believe it is based on Echo in Utah. There is Coalville and the Echo Reservoir right next to it as well as the locations general look/feel and various aspects of the town.
Not to mention the Wikipedia page on Echo does mention the VN and how it is 'loosely based on Echo and the surrounding area'.
Just remember it is a fictional town so doesn't necessarily have to be based on real location, even if we would like it to be ;)