Double majoring will require extra courses beyond what can be done in 8 semesters; would have to have a lot of AP or CLEP, maybe going in at a high level of math already. However if some requirements can be done over the summer, or maybe taking a course while interning/co-oping, a possibility.
Even in a large engineering program, some courses are only offered a particular term, so working that out too. DD is double majoring within her civil eng major, and is taking 3 courses during the summer between junior and senior year - says she can finish it and graduate on time. She had 3 extra upper division classes. The summer schedule comes out at the same time the fall schedule does, so she will see what she can take in the summer and how her schedule can work out in fall. The remaining spring courses are the ones either left or that are just offered in spring.
Student may need to decide early on what they are willing to do to complete what they want.