Do I have recourse if my general contractor sent me a bill for an additional $30K 9 months after the construction completed?

The answer is dependent upon many factors including: 1) Terms of your contract 2) Is this bill for extra work and if so was that work approved and performed correctly 3) Are you receiving the benefit of that work. I would recommend that your organization consult with a local attorney whose practice is concentrated in construction law so you can review the details of the project, including the contract, loan documents and any change orders.