Walnut conducts heavy lift aids-to-navigation operations, and law enforcement, homeland security, environmental pollution response, and search and rescue as directed.

[2] Walnut has an area of responsibility within the Fourteenth Coast Guard District of approximately 60,000 square miles and includes the Hawaiian Islands chain as well as American Samoa.

[4][5] After leaving the shipyard and finishing outfitting at the Coast Guard Yard at Curtis Bay, Maryland, Walnut transited the Panama Canal and arrived at her home-port of Honolulu on 29 May 1999.

She departed Hawaii on 18 January 2003, arriving in Persian Gulf waters just prior to the invasion of Iraq by coalition forces led by the United States.

She also participated in search and rescue operations, towing and logistical assistance, UN sanctions enforcement boardings, and standby for oil recovery duties.