Casa Grande Ruins National Monument Boundary Modification Act of 2010 - Authorizes the Secretary of the Interior to acquire only from willing sellers the private or state lands or interests identified on the map entitled "Proposed Casa Grande Ruins Boundary Modification" and dated January 2010.
Transfers administrative jurisdiction of specified withdrawn federal lands administered by the Bureau of Land Management (BLM) or the Bureau of Indian Affairs (BIA) to the National Park Service (NPS).
Transfers to the BIA the administrative jurisdiction of certain federal land administered by the NPS for purposes of the San Carlos Irrigation Project.
Requires the Secretary to administer all such transferred or acquired lands as part of the Casa Grande Ruins National Monument in Arizona.
Authorizes the Secretary to enter into an agreement with the state of Arizona to provide for cooperative management of specified state trust lands.
Directs the Secretary to conduct a study to identify any additional lands considered appropriate to become part of any further adjustments to the boundary of the Monument.