If you are interested in doing business with the U.S. Army Corps of Engineers, the first step is to register within the System for Award Management (SAM): https://sam.gov/SAM/pages/public/index.jsf

Information about the Jacksonville District Small Business Program can be found here: https://www.saj.usace.army.mil/SmallBusiness/

Subcontracting opportunities are usually done in partnership with larger companies. The Small Business Association can best help with that issue: https://www.sba.gov