This Corrective Action Investigation Plan (CAIP) contains project-specific information for conducting site investigation activities at Corrective Action Unit (CAU) 554: Area 23 Release Site, Nevada Test Site, Nevada. Information presented in this CAIP includes facility descriptions, environmental sample collection objectives, and criteria for the selection and evaluation of environmental samples. Corrective Action Unit 554 is located in Area 23 of the Nevada Test Site, which is 65 miles northwest of Las Vegas, Nevada. Corrective Action Unit 554 is comprised of one Corrective Action Site (CAS), which is: -23-02-08, USTs 23-115-1, 2, 3/Spill 530-90-002 This site consists of soil contamination resulting from a fuel release from underground storage tanks (USTs).