A composition for remediation of soil and groundwater containing halogenated compounds. The remediation composition includes an elemental iron-based composition, which may include activated carbon capable of absorbing the halogenated compounds with numerous pores impregnated with elemental iron. The remediation composition further includes a first bioremediation material including a blend of one-to-many organisms capable of degrading the halogenated compounds. The remediation composition includes an organic compound or polymeric substance and a second bioremediation material including a blend of one-to-many organisms capable of degrading the organic compound or polymeric substance over time (e.g., 20 to 365 or more days to provide a time release substrate-creating material or platform) into smaller molecules or compounds used by the organisms in the first bioremediation material while degrading the halogenated compounds. The organic compound may be a complex carbohydrate such as food grade starch, chitin, or other complex carbohydrate such as one with low water solubility.