Summary

Background

	BNL's Environmental Management System includes a comprehensive groundwater protection program that relies heavily on pollution prevention--using operational and engineered controls to prevent contamination from entering the groundwater. Since a sole source aquifer is beneath our facility, is it a priority for BNL to protect that resource.
	A supporting element of the groundwater protection program is the monitoring program, used to determine whether or not the controls are effective and whether there are other problems that need to be addressed. There are over 700 monitoring wells onsite -- most of which are associated with Environmental Restoration program, and others that monitor water quality at boundaries and near potable drinking water supplies.
	As part of the Groundwater Monitoring Improvements Project, more than 80 additional wells have been recently installed around active research and support operations across the Laboratory. We expect that some of these wells may detect problems in these operational areas, and will use the monitoring data to help determine what corrective actions may be needed, and whether the corrective actions are effective.

Groundwater Data

	The predominant groundwater flow direction in the E-20 catcher area is to the south-southeast. The depth to groundwater is approximately 28 to 30 feet below land surface, and the area is underlain by predominantly fine to coarse-grained sand and fine gravel.
	In December 1997, four Geoprobe wells were installed approximately 500 feet south-southeast (downgradient) of the E-20 area as part of an effort to evaluate general groundwater quality in the AGS area (conducted by the Environmental Restoration Program’s Preliminary Assessment/Site Investigation Project). Groundwater samples collected from one of these wells contained very low concentrations of tritium (approximately 560 pCi/L; or 3% of the drinking water standard of 20,000 pCi/L) and sodium-22 (24 pCi/L; or approximately 6% of the drinking water standard of 400 pCi/L). Both tritium and sodium-22 were non-detectable in samples from the other wells.
	As part of the Brookhaven National Laboratory’s Groundwater Monitoring Improvements Plan, (available online at http://www.bnl.gov/esd/gw.htm), a series of new groundwater monitoring wells were installed near a number of C-A Department beam stop, collimator and target areas, where soil activation was known or expected to occur. In early 1999, two permanent monitoring wells (064-055 and 064-056) were installed approximately 100 feet south-southeast of the E-20 catcher to better monitor groundwater quality in this region. These wells are spaced approximately 60 feet apart and abut the northwest side of Building 911 (Figure 1).
	Monitoring conducted since May 1999 showed that concentrations of tritium varied from non-detect to 5,800 pCi/L in one of the wells (064-056). Sodium-22 was detected in both wells at concentrations up to 70 pCi/L. Table 1 summarizes the calendar year 1999 monitoring data from permanent Wells 064-055 and 064-056.
	Because Well 064-056 might have been located on the edge of a more concentrated plume, BNL decided to install four additional temporary wells to further define the extent of tritium and sodium-22 in this area.
	Four Geoprobe wells were installed in January 2000. Detectable levels of tritium and sodium-22 were found in samples from three of the four temporary wells (Figure 1). The well installed furthest to the northeast (064-063) did not contain tritium or sodium above detectable levels. The highest concentrations of sodium-22 and tritium were found in well 064-065 at concentrations of 704 pCi/L and 40,400 pCi/L, respectively. These wells are located approximately 12’ and 24’ southwest of permanent well 064-056 respectively. Table 1 summarizes the results for the four Geoprobe wells.
	At a distance of approximately 100 feet downgradient of the E-20 catcher, the zone of elevated tritium and sodium-22 is estimated to be approximately 20 to 30 feet wide and situated within 10 feet of the water table (approximately 30 to 40 feet below land surface).
	As with the other beam stop areas, the E-20 is not within the immediate capture zone of any drinking water supply well, so public health is not impacted.

Corrective Actions

	In accordance with BNL's draft Groundwater Contingency Plan, regulators and the public were notified of our findings and planned corrective actions.
	BNL is in the process of installing a new cap over the E-20 catcher area to prevent further leaching of activation products. This technology has proven very successful in other areas onsite.
	BNL will install additional temporary wells to better define the downgradient extent of the plume, and may install additional permanent wells for long-term monitoring.
	Evaluation of any other actions required continues.