A district may refinance any indebtedness incurred pursuant to Section 16576 by borrowing from the United States or any of its agencies and issuing in connection therewith evidences of indebtedness in the form and upon the terms required by the United States or its agency. The sum so borrowed shall not exceed the amount of the obligation being refinanced, and interest shall not exceed 8 percent per year. The money so borrowed for refinancing shall be used only to repay the obligation for the retirement of which the money was borrowed.