Emerald Laija from the Federal Facilities Restoration and Reuse Office will discuss groundwater remediation at the central portion of the Hanford Site located in south-eastern Washington state. The presentation will provide a brief overview of the remedies for two groundwater operable units (OUs), the 200 West pump-and-treat (P&T) facility, and an optimization study being conducted for these remedies.
The 200 West P&T facility and associated well network is one of the key components of the final remedy selected for the 200-ZP-1 OU (2009) and the 200-UP-1 OU interim remedial action (2012). The selected remedy for both the 200-ZP-1 and 200-UP-1 OUs is a combination of P&T, monitored natural attenuation (MNA), flow-path control, and institutional controls (ICs). The 200-ZP-1 OU COCs include carbon tetrachloride, total chromium, hexavalent chromium (Cr(VI)), nitrate, trichloroethene (TCE), iodine-129, technetium-99, and tritium. The 200-UP-1 OU also has uranium. The 200-ZP-1 OU includes several groundwater contaminant plumes collectively covering an area of approximately 18 km2 (7 mi2). The major waste streams that contributed to groundwater contamination were associated with plutonium-finishing operations. The sediment thickness in the area above the water table ranges from 40 to 75 m (132 to 246 ft).
The 200 West P&T facility was originally designed with a capacity to treat 2,500 gallons per minute (gpm) of extracted groundwater using two treatment trains - one for radionuclides and the other for biological treatment. Biological treatment included use of fluidized bed reactors (FBRs), membrane bioreactors (MBRs), and air strippers. An optimization study is being conducted during the operations and maintenance (O&M) phase to suspend biological treatment using the FBRs and MBRs while adding an additional air stripper to increase the 200 West P&T capacity to approximately 14,200 L/min (3,750 gal/min).
Times listed are Eastern.