Y-12 Groundwater Protection Program Monitoring Optimization Plan for Groundwater Monitoring Wells at the U.S. Department of Energy Y-12 National Security Complex, Oak Ridge, Tennessee

This document is the monitoring optimization plan for groundwater monitoring wells associated with the U.S. Department of Energy (DOE) Y-12 National Security Complex (Y-12) in Oak Ridge, Tennessee (Figure 1). The plan describes the technical approach that will be implemented under the Y-12 Groundwater Protection Program (GWPP) to focus available resources on the monitoring wells at Y-12 which provide the most useful hydrologic and water-quality monitoring data. The technical approach is based on the GWPP status designation for each well (Section 2.0). Under this approach, wells granted ''active'' status are used by the GWPP for hydrologic monitoring and/or groundwater sampling (Section 3.0), whereas well granted ''inactive'' status are not used for either purpose. The status designation also determines the frequency at which the GWPP will inspect applicable wells, the scope of these well inspections, and extent of any maintenance actions initiated by the GWPP (Section 4.0). Details regarding the ancillary activities associated with implementation of this plan (e.g., well inspection) are deferred to the referenced GWPP plans and procedures (Section 5.0). This plan applies to groundwater monitoring wells associated with Y-12 and related waste management facilities located within three hydrogeologic regimes (Figure 1): the Bear Creek Hydrogeologic Regime (Bear Creek Regime), the Upper East Fork Poplar Creek Hydrogeologic Regime (East Fork Regime), and the Chestnut Ridge Hydrogeologic Regime (Chestnut Ridge Regime). The Bear Creek Regime encompasses a section of Bear Creek Valley (BCV) immediately west of Y-12. The East Fork Regime encompasses most of the Y-12 process, operations, and support facilities in BCV and, for the purposes of this plan, includes a section of Union Valley east of the DOE Oak Ridge Reservation (ORR) boundary along Scarboro Road. The Chestnut Ridge Regime is directly south of Y-12 and encompasses a section of Chestnut Ridge that is bound to the west by a surface drainage feature (Dunaway Branch) and by Scarboro Road to the east. The GWPP maintains an extensive database of construction details and related information for the monitoring wells in each hydrogeologic regime (including wells that have been destroyed or intentionally plugged and abandoned); the most recent hardcopy version of the database was issued in February 2003 (BWXT Y-12, L.L.C. [BWXT] 2003). This plan does not apply to temporary piezometers or other specialized groundwater monitoring/sampling devices that have been or may be installed for research purposes, hydrologic tests, pilot studies, or short-term investigations. This plan will be reviewed and updated in accordance with the schedule required in the Y-12 GWPP Management Plan (BWXT 2001). Between scheduled updates of this plan, any substantial changes or modifications to the plan, including changes in the GWPP status designation for each monitoring well identified in the plan, will be described in addenda issued by the GWPP Manager (or authorized designee). Information included in the addenda will be incorporated into the plan during the next scheduled update