We pour enclosure pads and the approach slab in front of them so the truck's front wheels sit on concrete, not on the asphalt lot. Pads are sloped to drain, built to the thickness on your plans, and set at the right height for the enclosure walls and gates.
Nampa's Design Review Guidelines (section 2.2) say trash receptacles go in service areas at the side or rear of a site, not visible from abutting streets, and screened with durable materials such as CMU block that match the main building. The City gives staff some flexibility on location, with input from the trash hauler on access. That means the pad location is usually set during design review, and we build to the approved site plan.