Final report of the second dye-tracer test at the Chesnut Ridge Security Pits, Y-12 Plant, Oak Ridge, Tennessee

Martin Marietta Energy Systems, Inc. (Energy Systems) manages a closed hazardous waste disposal unit, Chestnut Ridge Security Pits (CRSP), in the form of two trenches and several auger-holes, located on top of the eastern portion of Chestnut Ridge at the Department of Energy (DOE) Oak Ridge Y-12 Plant in Tennessee. The groundwater monitoring system for the unit presently consists of a network of upgradient and downgradient monitor wells. To investigate the discharge of groundwater to springs and streams, Energy Systems, through Geraghty and Miller, Inc., conducted an initial dye-tracer study during the driest part of 1990. The dye was detected at some of the monitoring sites, but verification was necessary due to the proximity of some sites to extraneous dye sources. Based on the results of the initial study, Energy Systems recommended to the Tennessee Department of Environment and Conservation (TDEC) in the 1990 Groundwater Quality Assessment Report (GWQAR) (HSW 1991) for the CRSP that a second dye-tracer study be conducted during the wet weather season. The procedures and materials were reviewed, and a field inspection of the monitoring sites was performed in the fall of 1991. The actual test commenced during the first week of February 1992 with a 4-week baseline monitoring period to determine the inherent variability of the emission spectra within the wavelength range characteristic of Rhodamine WT (RWT) and Fluorescent Brightener 28 (FB28) or similar naturally occuring compounds within in the aquifer. This is commonly referred as background in discussion of minimum detectable levels of dyes. On March 13, RWT and FB28 were injected; weekly monitoring began with the collection of the first set of detectors on March 19. The test was originally scheduled to conclude after 12 weeks but was extended to 18 weeks when no definitive results were obtained