Phase I remedial investigation report for the 300-FF-5 operable unit, Volume 1

Abstract

Areas (Figure 1-1). The 200 Areas contain waste management facilities, inactive irradiated fuel reprocessing facilities, and the 200 North Area (formerly used for interim storage and staging of irradiated fuel). Several waste sites in the 600 Area, located near the 200 Areas, also are included in the 200 Areas NPL site. The 200 Areas NPL site is in a region referred to as the 'Central Plateau' and consists of approximately 700 waste sites, excluding sites assigned to the tank farm waste management areas (WMAs). The 200-ZP-1 Groundwater Operable Unit (OU) consists of the groundwater located under the northern portion of the 200 West Area. Waste sources that contributed to the 200-ZP-1 OU included cribs and trenches that received liquid and/or solid waste in the past from the Z Plant and T Plant aggregate areas, WMA-T, WMA-TX/TY, and the State-Approved Land Disposal Site (SALDS). This feasibility study (FS) for the 200-ZP-1 Groundwater OU was prepared in accordance with the requirements of CERCLA decision documents. These decision documents are part of the Administrative Record for the selection of remedial actions for each waste site and present the selected remedial actions that are chosen in accordance with CERCLA, as amended by the Superfund Amendments and Reauthorization Act of 1986, and to the extent practicable, the NCP. This FS conforms to the conditions set forth in the Hanford Federal Facility Agreement and Consent Order (Tri-Party Agreement) (Ecology et al. 2003) and amendments, signed by the Washington State Department of Ecology (Ecology), EPA, and DOE Richland Operations Office (RL). This also includes Tri-Party Agreement Milestone M-015-00C for completing all 200 Area non-tank farm OU pre-Record of Decision (ROD) documents on or before December 31, 2011. This FS supports the final remedy selection for the 200-ZP-1 OU, as described in the Remedial Investigation/Feasibility Study Work Plan for the 200-ZP-1 Groundwater Operable Unit (referred to as the 200-ZP-1 RI/FS work plan) (DOE/RL-2003-55), as agreed upon by RL and EPA. Tri-Party Agreement Milestone M-015-48B required Draft A of the 200-ZP-1 OU FS and proposed plan to be transmitted to EPA by September 30, 2007. As agreed to with EPA in the 200 Area Unit Managers Meeting Groundwater Operable Unit Status (FH-0503130), the baseline risk assessment (BRA) was delayed from inclusion in the remedial investigation (RI) report and is completed and documented in this FS. The Remedial Investigation Report for 200-ZP-1 Groundwater Operable Unit (referred to as the 200-ZP-1 RI report) (DOE/RL-2006-24) included an evaluation of human health and ecological risks and hazards. The RI report identified the radiological and chemical contaminants of potential concern (COPCs) that represent the primary risks to human health and the environment. The complete risk assessment in this FS incorporates additional analytical data from the unconfined aquifer that were obtained during or after preparation of the RI report, particularly for carbon tetrachloride and technetium-99. This FS also includes the initial results from an ongoing study of technetium-99 contamination near WMA-T, the sampling of new wells near the 216-W-LC laundry waste crib and T Plant, updated Hanford vadose zone fate and transport modeling, and groundwater particle-tracking analysis. The purpose of this FS is to develop and evaluate alternatives for remediation of the groundwater in the 200-ZP-1 OU. The alternatives considered provide a range of potential response actions (i.e., no action; institutional controls and monitored natural attenuation [MNA]; and pump-and-treat with MNA, flow-path control, and institutional controls) that are appropriate to address site-specific conditions. The alternatives are evaluated against seven of the nine CERCLA evaluation criteria defined in Guidance for Conducting Remedial Investigations and Feasibility Studies Under CERCLA (EPA/540/G-891004). The remaining two CERCLA criteria will be formally assessed during the public comment period. The FS evaluation serves as the basis for identifying a remedy to mitigate potential risks to human health and the environment. A preferred alternative (or alternatives) will be presented to the public for review and comment in the proposed plan.