The Fiber Optic Photochemical Oxidation Decontamination (FOPOD) method and apparatus is provided for in-situ remediation of aqueous leachate plumes. The apparatus consists of a well-type housing with numerous holes drilled for a distance equal to the vertical depth of the leachate plume. The bottom of the housing is capped. Through the holes are threaded numerous specialty optical fibers, being encased in the housing and forming bundles above ground. The method comprises ultraviolet light perpendicular to the bundles being transmitted sub-surface by the optical fibers which exit each hole within the plume. Hydrogen peroxide injected into the housing also enters the plume through the numerous holes in the housing. The reaction products are carbon dioxide and water.