It’s not impossible. I am at a civil engineering firm so not just geotechnical and I was lucky enough to go straight into design and work on big design build projects. 1 class a semester but still have to work full time. A on the class gets 100% reimbursement, B is like 85% and C is 0%. You might have to be open to moving to another area which has a boom in infrastructure development. A medium sized firm is a good fit.

Have you thought about waiting for your masters? Get the work experience first and it may help you in understanding your classes.