I'm sorry that I can't fully answer that question. I'm not clear about the relationship between an Engineer job in the Army & the Army Corps of Engineers. If you enlist in the Army with a series-MOS 21 Engineer job you'll have to finish your enlistment obligations. When you get close to the end of your enlistment you can & are encouraged to apply for jobs in the civilian sector. There are certain benefits of joining before seeking a civilian position. You'll get additional training & experience & you always have the possibility of applying for a slot in Officer Candidate School for a commission. You can also try to enlist with a 09S contract. You would go to Basic & from there to OCS. The problem with that plan is you might not get a commission in the Engineering field. I can't really say whether your degree would help getting commissioned as an Engineer Officer. There's an Order of Merit List that determines if you'll get the job of your choice from a list that you develop. Those with the best class standing usually get their first choice if there are available slots. The only Officers that can be guaranteed their job when the come into the Army are Doctors & Lawyers. Maybe a few more. They usually come in direct-commissioned with the right degrees & credentials.

I'm sure there must be a web site for Army Corps of Engineers (it seems there's a web site for everything). You might get a point of contact for applying for a job with them & get some advice on what's the best course of action for you.