The Hanford Site, in southeast Washington State, is preparing to disposition approximately 56,000,000 gallons (56 Mgal) of radioactive and chemically hazardous wastes currently stored in underground tanks at the site. Tank wastes will be divided into a high-activity fraction and a low-activity fraction for subsequent treatment and disposition. A waste processing and treatment facility, the Waste Treatment and Immobilization Plant (WTP), will include the high-level waste (HLW) vitrification facility (WTP HLW Vitrification Facility) for immobilizing the high-activity fraction and a low-activity waste (LAW) vitrification facility (WTP LAW Vitrification Facility) for immobilizing the low-activity fraction. Both facilities will use vitrification technology to immobilize the Hanford tank wastes in a glass waste form. Revision 0 Draft DRAFT Volume I | viii Revision 0 Draft DRAFT Volume I | ix The FFRDC team makes the following recommendation: DOE should expeditiously secure and implement multiple pathways for off-site grout solidification/ immobilization and disposal of LAW in parallel with direct-feed low-activity waste (DFLAW) vitrification process.This recommendation is based on a technical evaluation of multiple alternatives considering (1) long-term effectiveness (environmental and safety risk after disposal), (2) implementation schedule and risk (environmental and safety risks prior to mission completion, including risks driven by waste tank storage duration), (3) likelihood of successful mission completion (including affordability and robustness to technical risks), and (4) lifecycle costs (discounted). The intent of multiple pathways is to provide parallel contractual agreements with multiple facilities for off-site solidification/immobilization and disposal to minimize risks associated with potential facility-or state-specific implementation challenges.The recommended approach can be beneficial in many ways, including:• Provides the capability to achieve the most rapid reduction in the amount of waste stored in the Hanford single-shell tanks (SST) and double-shell tanks (DST) by using available off-site solidification/immobilization and disposal capacity, and therefore results in the most rapid reduction in risk to human health and the environment attributed to potential future unplanned tank waste releases.• Provides additional long-term environmental protection, including to the aquifers underlying the Hanford Site and the Columbia River, by disposing of a significant portion of the inventory of risk-driving constituents (e.g., 99 Tc, 129 I) at off-site facilities that are located in geologic settings with low infiltration and do not have credible pathways to potable water aquifers.• Provides flexibility in the available treatment technologies and disposal pathways, and reduces the potential for individual choke points to further delay the Hanford tank waste treatment and disposal mission. Concurrent LAW vitrification and solidification/immobilization treatment and disposal pathways would allow LAW routing b...