This U.S. Geological Survey (USGS) Data Release describes field methods, lab methods, and data for groundwater and soil gas samples collected in the vicinity of the Red Hill Bulk Fuel Storage Facility, O‘ahu, Hawai‘i, from September 2022 through April 2023. The Red Hill facility consists of 20 underground fuel storage tanks that can each hold approximately 12.5 million gallons of fuel and are connected through a network of service tunnels and fuel pipelines. The data in this release were collected to understand better the distribution and directional flow of ancient carbon from past petroleum releases in the subsurface at the Red Hill Bulk Fuel Storage Facility. Table 1 of this data release contains site and sample information, analytical results, methods, and lab information for each result. Analytical data for groundwater include field water quality characteristics, methane (CH4), major ions, trace metals, alkalinity, nonvolatile dissolved organic carbon (NVDOC), carbon-14 (14C) content of NVDOC, and diesel range organics (DRO). Analytical data for soil gas samples include carbon dioxide (CO2) efflux, soil temperature, soil moisture, CO2 concentrations, and 14C content of CO2. The codes used in Table 1 are defined in the metadata. Table 2 of this data release contains detailed well information. Table 3 contains the laboratory detection and reporting limits for Reston Biogeochemical Processes on Groundwater Laboratory, Reston, VA (RBPGL). Table 4 contains interim values from soil carbon traps and cartridges provided by E-flux, LLC used in the calculation of ancient CO2 efflux and modern CO2 efflux.