The best amendment for soils to improve soil structure is to add organic matter - and the best organic matter is in the form of well aged compost. Fully composted organic matter can be purchased at nursery and box stores and also at the Salt Lake City Landfill, but you can also produce your own using kitchen waste, lawn clippings, fall leaves. Sometimes folks put in manure or leaves directly in the soil, however, high salt content, weed seeds are problems you don't want to introduce into your soils. By first composting manure, leaves and other materials you can produce great organic matter that will improve soil structure. Here is the link to USU publication on backyard composting, https://extension.usu.edu/files/publications/factsheet/HG-Compost-01.pdf .