Final answer:
If proposed excavation activities are near a critical facility, the federal agency responsible for approving the project must be notified. They will work with State Historic Preservation Offices (SHPOs), Tribal Historic Preservation Offices (THPOs), and other consulting parties to address any potential adverse effects and mitigate them.
Step-by-step explanation:
If proposed excavation activities are near a critical facility, the group that must be notified is the federal agency responsible for approving the excavation project. According to the information provided, if there is a potential adverse effect on the critical facility, the federal agency must seek concurrence from appropriate State Historic Preservation Offices (SHPOs), Tribal Historic Preservation Offices (THPOs), and other consulting parties. They will then negotiate mitigation terms and solidify them into a memorandum of agreement to ensure completion of the agreed-upon mitigation measures.