Keep accurate documentation as to the delays and costs and charge them for it. Sounds like they have not had a issued a contract like this before. You are incurring some very real costs, the only way for the agency to learn is to charge them for your down time. All of these windows that you can operate have to be in the contract. Since they are not you can charge them for it and you will be successful. The USFS gets dinged like this all the time, it is very common here.