Groundwater Protection Program Calendar Year 1998 Evaluation of Groundwater Quality Data for the Chestnut Ridge Hydrogeologic Regime at the U.S. Department of Energy Y-12 Plant, Oak Ridge, Tennessee

The Chestnut Ridge Hydrogeologic Regime (Chestnut Ridge Regime) encompasses a section of Chestnut Ridge south of the U.S. Department of Energy (DOE) Y-12 Plant (Figure 1). Groundwater monitoring is performed at several hazardous and nonhazardous waste management facilities located in the regime per the requirements of applicable operating/post closure permits and governing state/federal regulations and guidelines, including DOE Order 5400.1A - General Environmental Protection Program. Applicable provisions of DOE Order 5400.1A require evaluation of available monitoring data with regard to: (1) groundwater quality in areas that are, or could be, affected by Y-12 Plant operations, (2) the quality of surface water and groundwater where contaminants are most likely to migrate beyond the DOE Oak Ridge Reservation (ORR) property line, and (3) long-term trends in groundwater quality at the Y-12 Plant. This report presents the results of these DOE Order 5400.1A evaluations based on available data for the network of monitoring wells and springs in the Chestnut Ridge Regime sampled during calendar year (CY) 1998. The following sections of this report contain relevant background information (Section 2.0); describe the results of the respective data evaluations required under DOE Order 5400.1A (Section 3.0); summarize significant findings of each evaluation (Section 4.0); and list the technical reports and regulatory documents cited for more detailed information (Section 5.0). All of the illustrations (maps and trend graphs) and data summary tables referenced in each section are presented in Appendix A and Appendix B, respectively