Results of Phase I groundwater quality assessment for single-shell tank waste management areas T and TX-TY at the Hanford Site

Abstract

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or impiy its endorsement, m mmendattion, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. summary Pacific Northwest National Laboratory (PNNL) conducted a Phase I, Resource Conservation and Recovery Act of 1976 (RCRA) groundwater quality assessment for the Richland Field Office of the U.S. Department of Energy (DOE-RL) under the requirements of the Federal Facility Compliance Agreement. The purpose of the investigation was to determine if the Single-Shell Tank Waste Management Areas (WMAs) T and TX-TY have impacted groundwater quality. Waste Management Areas T and TX-TY, located in the northern part of the 200 West Area of the Hanford Site, contain the 241-T, 241-TX, and 241-TY tank farms and ancillary waste systems. These two units are regulated under RCRA interim-status regulations (under 40 CFR 265.93) and were placed in assessment groundwater monitoring because of elevated specific conductance in downgradient wells. Anomalous concentrations of technetium-99, chromium, nitrate, iodine-129, and cobalt-60 also were observed in some d o w m e n t wells. Phase I assessment, allowed under 40 CFR 265, provides the owner-operator of a facility with the opportunity to show that the observed contamination has a source other than the regulated unit. For this Phase I assessment, PNNL evaluated available information on groundwater chemistry and past waste management practices in the vicinity of WMAs T and TX-TY. Background contaminant concentrations in the vicinity of WMAs T and TX-TY are the result of several overlapping contaminant plumes resulting from past-practice waste disposal operations. This background has been used as baseline for determining potential WMA impacts on groundwater. Examination of contaminant patterns in downgradient wells at the two WMAs indicate that: Elevated values of specific conductance in downgradient wells 299-W10-15 (WMA T) and 299-WlO-17 (WMA TX-TI) are a result of elevated concentrations of sodium and nitrate originating outside of the WMAS. Elevated technetium-99 and co-contaminants (e.g., chromium, tritium, and nitrate) observed in well 299-Wll-27, immediately d o w n w e n t to WMA T, are the result of a contaminant source within the WMA. Contaminant chemistry is consistent with a small volume tank waste source and l...

Groundwater Quality Assessment for Waste Management Area U: First Determination

“…In addition, variation of concentrations with the changing direction of groundwater flow indicates a source within the southern portion of the W'MA. Ratios of mobile contaminants (e.g., chromium, nitrate, technetium-99, tritium) are useful in identifying tank waste components and mixing trends in groundwater (Johnson and Chou 1998;Hodges 1998). Plots of nitrate/technetium-99 versus technetium-99 ( Figure 5.2) indicate that the data is consistent with the observed groundwater contamination being the result of mobilization and dilution of tank waste by infiltrating surface water.…”

“…The direction of groundwater flow in the vicinity of WMA U has varied because of changing effluent discharge sites within the 200 West &ea (Hodges 1998). The direction of groundwater flow, at the time when the RCIU4 detection network was established, was toward the northeast (Caggiano and Goodwin 1991).…”

RCRA Groundwater Monitoring Plan for Single-Shell Tank Waste Management Area A-AX at the Hanford Site

“…Johnson and Chou (1998) discuss the extent that rapid snowmelt from recent years has contributed to natural driving forces. The results of a rapid snow melt event in February 1979 are documented in Hodges (1998) with photographs showing extensive flooding in the 241-T Tank Farm. The effects of these events can be enhanced by gravel surfaces, lack of plant uptake and transpiration, and surface depressions that tend to collect and pond run-off and snow melt.…”

RCRA Assessment Plan for Single-Shell Tank Waste Management Area TX-TY at the Hanford Site

“…In September 1993 technetium-99 reached a maximum activity of 12,200 pCi/L, 14 times the drinking water standard (DWS) of 900 pCi/L; iodine-129 reached an activity of 64.2 pCi/L, 64 times the DWS; and tritium reached an activity of 564,000 pCi/L, 28 times the DWS. The first determination (Hodges 1998) concluded that: 1) elevated technetium-99 and co-contaminants (e.g., chromium, tritium, nitrate, iodine-129, etc.) in well 299-W14-12 is consistent with a source within the WMA and contaminant chemistry is consistent with a small volume tank waste source; and 2) an upgradient source (the 216-T-25 Trench) is possible.…”

“…As a result of the first determination (Hodges 1998), a RCRA Facility Investigation/Corrective Measures Study (RFI/CMS) will be initiated at WMA T and WMA TX-TY. The primary focus of the1.7 schedule and activities for the RFI/CMS are described in the Hanford Federal Facility Agreement and Consent Order (Tri-Party Agreement, Ecology et al 1989), Change .…”