Plans and Practices for Groundwater Protection at the Los Alamos National Laboratory Interim Status Report (2006) / Chapter Skim
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Interim Status Report
Interim Status Report
Pages 1-24
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Environmental Protection Agency (EPA) , the State of New Mexico regulates protection of its water resources through the New Mexico Environment Department (NMED)
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The Radioactive Liquid Waste Treatment Facility in TA-50 is the only location where liquid radioactive waste continues to be discharged to the environment.
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The first two subsets of tasks direct the committee to provide answers to questions regarding LANL's knowledge of potential sources of groundwater contamination and aspects of its monitoring program. The committee's final report will address these questions and provide recommendations as requested in the last portion of the task statement.
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2. Specific data-quality issues: Is the laboratory following established scientific practices in assessing the quality of its groundwater monitoring data?
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Its purpose is to: · Accelerate the pace of investigation and cleanup of the LANL facility; · Prioritize investigation and cleanup activities; · Provide minimum investigation and reporting requirements; · Provide for cleanup requirements that meet state environmental standards; and · Provide schedules for completion of remedies by about 2015. The order contains the following: · Specific investigation requirements for high priority sites; · General characterization requirements for sites not yet addressed under the LANL environmental restoration program; · Requirements for selecting corrective actions; · Methods for establishing cleanup levels; · Methods and procedures for conducting corrective actions; · Reporting requirements; and · Schedule for reporting, work plan submittals, and corrective action completions.
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The perched groundwater generally contains greater concentrations of contamination than the underlying regional aquifer. Although it appears that discharges from LANL are the major sources of this contamination, there are also off-site sources -- for example, wastewater treatment plants near the site -- that make the origins and movements of some types of contamination (e.g., nitrate)
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. In that report LANL analyzed the effects of residual drilling fluids on samples taken from groundwater wells in the regional aquifer and evaluated the ability of these wells to provide representative measurements.
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James Bearzi, Chief of the NMED Hazardous Waste Bureau, gave an overview of the Consent Order and summarized LANL groundwater issues of regulatory significance. The second day of the meeting included a visit to the Pueblo de San Ildefonso, an overview tour of portions of the LANL site, and participation in an NNMCAB Groundwater Forum meeting at the Smith Auditorium in Los Alamos.
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DOE requires maintaining groundwater quality adequate for its highest beneficial use, which DOE considers to be extraction of drinking water from the regional aquifer. Environmental Protection Agency (EPA)
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Los Alamos National Laboratory LANL summarized its goals for groundwater protection during the opening session of the plenary, as follow (Dewart, 2006) : · Demonstrate compliance with applicable standards and regulations; · Protect the drinking water supplies of surrounding communities; · Protect the quality of groundwater moving from LANL to off-site locations; and · Protect the quality of water in springs and the Rio Grande.
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Groundwater monitoring and data quality. While recognizing that the topics of the breakout sessions are interconnected, committee members decided that organizing their technical discussions in these three tracks would be most efficient for gathering information to address the task statement, as described below.
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Sources of Contamination and Source Controls LANL is systematically investigating contaminant sources (principally liquid waste discharges and buried waste) and the nature and extent of releases under a prioritized sequence that is consistent with the Consent Order.
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The Radioactive Liquid Waste Treatment Facility in TA-50, which has operated since 1963, has been the only source of radioactive liquid discharges since 1986 (Rogers, 2006b)
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) Radioactive Mortandad Radioactive 1963-present tritium, nitrate, Liquid Waste Canyon wastewater perchlorate Treatment treatment Facility (TA-50)
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. Mortandad Canyon has been a priority for groundwater investigations because it has continued to receive discharges from the site's Radioactive Liquid Waste Treatment Facility since 1963.
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, travel times to the regional aquifer from surface sources are a function of two factors: infiltration rate and hydrogeology. · Travel times are in excess of 1000 years from mesas.
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. Highlights of the workshop discussion on flowpaths included the following: · The major liquid and solid waste sites and how well the LANL scientists believe they understand the movement of contaminants from these sites; · The major flowpath conceptualizations for each of the major sources and how well the LANL scientists believe they understand the flowpaths; · Numerical models of the vadose zone and regional aquifer and how well these models compare to the existing flow conceptualizations; · Multi-phase simulations of water and vapor at one of the mesa-top disposal sites; · Regional flow models and their use in evaluating the effectiveness of the existing groundwater monitoring system; · The difficulty in interpreting aquifer test data for characterizing anisotropy and heterogeneities; · Methods and utility of incorporating uncertainty into an analysis of contaminant transport; · Long-term stewardship discussions, with LANL staff noting that plans for long-term stewardship are still in the developmental stages; and · Remedial action plans for chromium in the groundwater.
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Source: Donathan Krier, LANL FIGURE 4 Diagram of a Multi-Screened Well. The well screens are locations at which groundwater can enter the well.
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, LANL undertook an analysis of the impacts of residual drilling fluids on the ability of the groundwater wells in the regional aquifer to provide representative measurements. Its purpose was to: · Evaluate whether the well screens are producing data that are reliable and representative of the intermediate groundwater and regional aquifer; · Provide a summary of the number of well screens that are producing reliable data and the number that are potentially impacted; and · Of the impacted screens, identify those that appear to be cleaning up over time and those that are the most problematic (Simmons, 2006b)
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Further, LANL agrees that some characterization wells may not be suitable for monitoring. LANL's goal, as prescribed by the Consent Order, is to transition to long-term groundwater monitoring in all watersheds throughout the site by 2015 (Dewart, 2006)
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Gilkeson stated that bentonite clay and/or organic drilling additives had invaded the screened intervals in all of the LANL characterization wells. He illustrated (see Figure 6)
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FIGURE 6 Reactive Contaminant Capture Barrier that Surrounds the Screened Intervals in the LANL Characterization Wells. Geologist Robert Gilkeson described how drilling fluids could form a zone that removes contaminants from sampled groundwater.
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Gilkeson provided a summary of his reasons that many of LANL's wells that penetrate the regional aquifer and some perched aquifers do not produce reliable and representative water quality data: · Drilling additives; · Corrosion of iron well screens in the older wells; · Construction errors that have plugged screens with bentonite clay; · Dilution of contamination by very long well screens; · Well screens in strata with low permeability rather than in strata with high permeability; and · Well screens too deep below the water table of the regional aquifer. As one case in point, Mr.
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24 Plans and Practices for Groundwater Protection Interim Report FUTURE PLANS FOR THIS STUDY The committee's information gathering is substantially completed. The remaining study period and meetings will be used primarily for deliberation, developing consensus on the findings and recommendations requested in the task statement, and producing the final report.
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