RCRA Assessment Plan for Single-Shell Tank Waste Management Area B-BX-BY at the Hanford Site

This document was prepared as a groundwater quality assessment plan revision for the single-shell tank systems in Waste Management Area B-BX-BY at the Hanford Site. Groundwater monitoring is conducted at this facility in accordance with 40 CFR Part 265, Subpart F. In FY 1996, the groundwater monitoring program was changed from detection-level indicator evaluation to a groundwater quality assessment program when elevated specific conductance in downgradient monitoring well 299 E33-32 was confirmed by verification sampling. During the course of the ensuing investigation, elevated technetium-99 and nitrate were observed above the drinking water standard at well 299-E33-41, a well located between 241-B and 241-BX Tank Farms. Earlier observations of the groundwater contamination and tank farm leak occurrences combined with a qualitative analysis of possible solutions, led to the conclusion that waste from the waste management area had entered the groundwater and were observed in this well. Based on 40 CFR 265.93 [d] paragraph (7), the owner-operator must continue to make the minimum required determinations of contaminant level and rate/extent of migrations on a quarterly basis until final facility closure. These continued determinations are required because the groundwater quality assessment was implemented prior to final closure of the facility