Statistical evaluation of effluent monitoring data for the 200 Area Treated Effluent Disposal Facility

The 200 Area Treated Effluent Disposal Facility (TEDF) consists of a pair of infiltration basins that receive wastewater originating from the 200 West and 200 East Areas of the Hanford Site. TEDF has been in operation since 1995 and is regulated by State Waste Discharge Permit ST 4502 (Ecology 1995) under the authority of Chapter 90.48 Revised Code of Washington (RCW) and Washington Administrative Code (WAC) Chapter 173-216. The permit stipulates monitoring requirements for effluent (or end-of-pipe) discharges and groundwater monitoring for TEDF. Groundwater monitoring began in 1992 prior to TEDF construction. Routine effluent monitoring in accordance with the permit requirements began in late April 1995 when the facility began operations. The State Waste Discharge Permit ST 4502 included a special permit condition (S.6). This condition specified a statistical study of the variability of permitted constituents in the effluent from TEDF during its first year of operation. The study was designed to (1) demonstrate compliance with the waste discharge permit; (2) determine the variability of all constituents in the effluent that have enforcement limits, early warning values, and monitoring requirements (WHC 1995); and (3) determine if concentrations of permitted constituents vary with season. Additional and more frequent sampling was conducted for the effluent variability study. Statistical evaluation results were provided in Chou and Johnson (1996). Parts of the original first year sampling and analysis plan (WHC 1995) were continued with routine monitoring required up to the present time