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GROUNDWATER
REMEDIATION PROGRAM AT BROOKHAVEN
NATIONAL LABORATORY UPTON, NEW YORK T.W. Burke1, W.R. Dorsch2, R.F. Howe1, D.B. Bennett2, D.E. Paquette2, V.J. Racaniello1,
K.C. Klaus2, and M.G. Hauptmann1 Environmental
Restoration1 Environmental and
Waste Management Services Division2 Brookhaven National Laboratory Upton, New York 11973 Introduction
The primary mission of BNL’s Environmental Restoration Program is to remediate soil and groundwater contamination, and to prevent additional contamination from migrating off the BNL site. The cleanup goals for groundwater are to: 1) prevent or minimize plume growth, and 2) reduce contaminant concentrations in the Upper Glacial aquifer to below regulatory standards within 30 years. The extent of volatile organic compound (VOC) and radionuclide contamination in groundwater in the central and southern areas of BNL is shown on Figure 1. Since the beginning of active groundwater remediation in 1997, more than 2,948 pounds of VOCs have been removed from the groundwater and over four billion gallons of treated water has been returned to the aquifer (Table 1). It is expected to take up to 10 years of aquifer treatment before widespread improvements in groundwater quality at BNL are achieved. Even so, some noticeable improvements in groundwater quality are evident by the successful cleanup of the Operable Unit (OU) IV VOC plume, and the reduction in size of the OU I and OU III VOC plumes and the High Flux Beam Reactor (HFBR) tritium plume. Active groundwater remediation activities are expected to continue until the year 2025. Treatment System Capacity
To restore groundwater quality in the Upper Glacial aquifer within the 30-year cleanup timeframe, BNL has plans to construct seventeen groundwater treatment systems with a total treatment capacity of about 4,500 gpm. Fourteen of these systems are designed to treat VOC contamination, whereas the remaining three will treat or control radionuclide contamination (e.g., strontium-90 and tritium). To date, eight of the seventeen planned groundwater treatment plants have been constructed, with a total groundwater cleanup treatment capacity of 2,575 gpm. Six groundwater remediation systems are currently in operation. In 2000 and 2001, two treatment systems (the OU IV Air Sparging/Soil Vapor Extraction (AS/SVE) system, and the HFBR Pump & Recharge System) were placed in standby mode, because they substantially met their cleanup goals. Figure 1 shows the locations of the current and planned groundwater treatment systems. Figure 1: Extent of groundwater contamination and locations of current and planned groundwater treatment systems (Note: the OU V eastern VOC plume and HFBR tritium plume are not shown).
Table 1: Groundwater Remediation Systems Treatment Summary for 1997 – 2001.
The remediation of radiologically contaminated groundwater began soon after the 1997 discovery of the HFBR tritium plume, and an engineering study is currently being conducted to determine the feasibility of treating several strontium-90 plumes. Hydraulic control was employed for the leading edge of the HFBR tritium plume beginning in 1997 using a pump and recharge system. This system pumped groundwater from the leading edge of the tritium plume, removed commingled VOC contamination by means of an air stripping tower, then it discharged the low-level tritiated water to an upgradient recharge basin. The goal was to prevent the plume from continuing to move downgradient, thereby ensuring that the plume remained on site to naturally decay and disperse. The system was placed on stand-by in September 2000 when continued groundwater characterization efforts verified that tritium concentrations in the southern segment of the plume were well below the 20,000 pCi/L drinking water standard. During 2000 and early 2001, low flow extraction of highly contaminated groundwater from the segment of the tritium plume that is closer to the reactor facility (source area) was undertaken to accelerate cleanup of the plume. A total of 95,000 gallons of groundwater were pumped from ten wells in twenty-one separate pumping events. The water was transported off-site for disposal at an Environmental Protection Agency approved facility. (Note: Tritium cannot be removed from groundwater using conventional treatment methods.) Remediation of strontium-90 contaminated groundwater is planned for the Brookhaven Graphite Research Reactor/Waste Concentration Facility (BGRR/WCF) area and the Chemical/Animal Holes area. A pilot study scheduled for 2003 at the Chemical/Animal Holes will test the feasibility of remediating groundwater containing high concentrations of strontium-90 by extracting it, treating it with synthetic zeolite resin, and recharge the treated water to the aquifer via dry wells. If the pilot study is successful, this technology could be used for strontium-90 contaminated water in the BGRR/WCF area. Table 2. Summary of current and planned BNL groundwater treatment systems.
(A): Water treated using air stripping tower. (C): Water or off-gas treated using activated
carbon. (I): Water treated using ion exchange. (O): Treatment system located off site. (*): Tritium cannot be removed from groundwater
using conventional treatment methods.
VOCs commingled with HFBR tritium plume were treated by
air stripping. |
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