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DOE Site: Y-12 Oak Ridge, TN EM Project: Mitigation/Remediation of Hg ETR-13 ETR Report Date: April 2008 United States Department of Energy Office of Environmental Management (DOE-EM) External Technical Review of the Mitigation and Remediation of Mercury Contamination at the Y-12 Plant, Oak Ridge, TN Why DOE-EM Did This Review 2. (cont’d) “Quick Wins” Creeks and Streams- (a) selective physical modification at areas of methylation and (b) addition of trace Se to reduce methylation and/or uptake current and projected reality should be added. What the ETR Team Found From 1953 to The review/workshop focused on mercury contamination in 1983, ~240,000 pounds of mercury (Hg) were the East Fork Popular Creek and how to reduce mercury released to the East Fork Popular Creek during the levels in the fish. The metrics for achieving cleanup vary operation of the Y-12 Plant. In 1963, direct according to the agency of interest; however, national data systematic releases of mercury stopped; however, suggest a clear trend toward the use of fish tissue mercury continues to be released into the creek concentration as the ultimate basis for setting standards. from various sources of contamination in the Y-12 A significant technical observation was that the level of Hg complex. Remediation completed up to 1992 found in the fish in the creek at Y-12 resulted from an resulted in an overall reduction of Hg loading from intricate series of chemical transformations that began with 150 g/day in 1983 to 15 g/day in 1992, with a the initial release of Hg followed by a series of changes as current goal of 5g/day or less. The objective was to the Hg was transported through the shallow soil, to the review the current ground and surface water Hg surface and/or shallow ground water, and then through the remediation strategy for adequacy in reducing Hg reach of the stream drainage. The concentration of Hg in the levels in the fish and to indentify opportunities to fish, a potential remedial action endpoint, is better correlated achieve cost and technical improvements and/or to with the concentration of methyl mercury in the stream. The address technical uncertainties. biogeochemical and microbial processes that form methyl What the ETR Team Recommended mercury from inorganic mercury are in the basic science regime and are being actively studied. Therefore, actions 1. The team recommended that a plan that logically that reduce the fraction of Hg converted to methyl mercury integrates the prioritized list of recommendations within stream water and/or sediment or actions that alter the into a coordinated technical approach be food chain dynamics are potentially important to addressing developed with the participation of affected Oak the impact of mercury at Oak Ridge. Recommendations Ridge organizations, state and federal regulators were made by evaluation of four action zones: buildings and and stakeholders. rubble, source zone soil, Outfall 200 area, and upper and 2. “Quick Wins” were recommended for near term lower reaches of the creek. The first two zones appeared to improvements as follows: have less direct importance than Outfall 200 and the upper Outfall 200- (a) use of stannous chloride in the NS and lower reaches of the creek in affecting the environmental Pipe to volatilize Hg, (b) addition of Hg impact of mercury contamination at the Y-12 Facility. sequestrants , and (c) use of sodium thiosulfate for dechlorination. To view the full ETR reports, please visit this web site: http://www.em.doe.gov/Pages/ExternalTechReviews.aspx July 2009 The purpose of an External Technical Review (ETR) is to reduce technical risk and uncertainty. ETRs provide pertinent information for DOE-EM to assess technical risk associated with projects and develop strategies for reducing the technical risk and to provide technical information needed to support critical project decisions. Technical risk reduction increases the probability of successful implementation of technical scope. In general, ETRs assesses technical bases, technology development, and technical risk identification and handling strategies. WSRC-STI-2008-00212 U.S. Department of Energy Office of Environmental Management EM Center for Sustainable Groundwater and Soil Solutions Recommendations to Address Technical Uncertainties in the Mitigation and Remediation of Mercury Contamination at the Y-12 Plant, Oak Ridge, Tennessee 21 April 2008 Oak Ridge, Tennessee Prepared for: U.S. Department of Energy Office of Environmental Management Engineering and Management (EM-20) DISCLAIMER Preparation of this report was coordinated by Washington Savannah River Company (WSRC) for the United States Department of Energy (US DOE) under Contract No. DE-AC09-96SR18500. Careful effort was made by the authors to assure the accuracy of the contents and interpretation. However, the USDOE nor WSRC, nor any of their employees makes any warranty, expressed or implied, or assumes any legal liability for accuracy, completeness, or usefulness, of information, apparatus, or product or process disclosed herein or represents that its use will not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, name, manufacturer or otherwise does not necessarily constitute or imply endorsement, recommendation, or favoring of same by WSRC or by the United States Government or any agency thereof. The views and opinions of the authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. Printed in the United States of America Prepared For U.S. Department of Energy Office of Environmental Management Engineering and Technology (EM-20) WSRC-STI-2008-00212 Department of Energy Office of Environmental Management (EM-22) EM Center for Sustainable Groundwater and Soil Solutions Recommendations to Address Technical Uncertainties in Mitigation and Remediation of Mercury Contamination at the Y-12 Plant, Oak Ridge, Tennessee Authors: Brian Looney, SRNL: Technical Lead Carol Eddy-Dilek, SRNL Ralph Turner, RT Geosciences George Southworth, ORNL Mark Peterson, ORNL Anthony Palumbo, ORNL Prepared for: Office of Engineering and Technology (EM-20) Paul Beam, EM-20 Representative Technical coordination and evaluation for this effort were provided by the Savannah River National Laboratory (Washington Savannah River Company (WSRC)) for the United States Department of Energy under Contract No. DE-AC09-96SR18500. Table of Contents TABLE OF CONTENTS ..................................................................................................I LIST OF FIGURES ......................................................................................................... II EXECUTIVE SUMMARY ............................................................................................III 1.0 INTRODUCTION................................................................................................. 1 2.0 HISTORY OF ENVIRONMENTAL REMEDIATION AT Y-12.................... 2 GENERAL BACKGROUND ................................................................................................. 2 PAST REMEDIAL EFFORTS................................................................................................ 2 ONGOING REMEDIATION AND RESEARCH EFFORTS ......................................................... 4 3.0 TECHNICAL ASSESSMENT............................................................................. 7 DESCRIPTION OF THE PROBLEM ....................................................................................... 7 TECHNICAL EVALUATION PROCESS ................................................................................. 7 KEY ASSUMPTIONS .......................................................................................................... 7 CONCEPTUAL MODEL OF MERCURY -- GENERAL........................................................... 10 CONCEPTUAL MODEL OF MERCURY IN THE EAST FORK POPLAR CREEK ....................... 13 TECHNICAL EVALUATION RESULTS – BASIC SCIENCE AND TECHNOLOGY..................... 16 TECHNICAL EVALUATION RESULTS – APPLIED SCIENCE AND ENGINEERING ................. 16 Subdomain I – Buildings / Rubble ............................................................................ 18 Subdomain II – Source Zone Soil.............................................................................. 18 Subdomain III – Outfall 200 Area ............................................................................ 27 Subdomain IV – Upper and Lower Reaches of Stream............................................. 35 4.0 RECOMMENDATIONS.................................................................................... 48 5.0 REFERENCES.................................................................................................... 50 i List of Figures Figure 1. Location Map of the EFPC and infrastructure in the Y-12 complex. ................ 3 Figure 2. Trends in water and fish concentrations............................................................. 8 Figure 3. Examples of divergent metrics for soil, sediment, groundwater and surface water............................................................................................................................ 9 Figure 4. Block diagram showing key mercury transformations..................................... 11 Figure 5. Summary depiction of site specific mercury conditions .................................. 15 Figure 6. Identitied Site Specific Subdomains................................................................

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