Monahan is the Deputy administrator of Commodity Operations (DACO) for USDA's Farm Service Agency (FSA). As Deputy Administrator for Commodity Operations, Monahan is responsible for developing policies and regulations for the dairy price support program; the storage, handling and disposition of Commodity Credit Corporation's owned commodities; and for the export and domestic commodity donation programs. Under Monahan's leadership, DACO produces a uniform regulatory system for the storage of agricultural products and ensures the timely provision of food products procured for domestic and international food assistance programs and market development programs.

Monahan most recently served as Executive Director of the Ag Council on the Environment where he built coalitions with producers, landowners, and groups to initiate, expand and support water quality projects. During the Clinton Administration, Monahan served as the State Executive Director for the FSA in Vermont and the Virgin Islands, and later as a special assistant to the FSA administrator. He served as a legislative assistant to Vermont Senator Leahy after serving for 15 years in USDA's Natural Resources Conservation Service. He is a disabled Marine from the Vietnam era and currently serves as a National Board Director for Veterans and Military Families for Progress, a nonprofit organization helping veterans and their families.

Monahan, a Vermont native, graduated from Johnson State College with a double major in environmental science and economics and resource management. He and his wife have three sons and reside in Maryland.