An underutilized pair of sites, owned by the State of Hawai’i, required investigation and cleanup in preparation for a ~$25 million redevelopment to be called Waikiki Landing (plans have changed since then). We followed up on previous environmental assessments and ruled out significant subsurface contamination at a former repair facility clearing the way for building demolition and new construction. A fueling facility was affected by residual contamination from a historic leaking underground storage tank system. We identified overloading of the aquifer by a sewage leak, exacerbating the petroleum contamination. Soil removal and remediation of the subsurface with calcium peroxide, an oxygen releasing agent, cleaned up the site and earned closure from the Hawai’i DOH.