Groundwater monitoring plan for the 183-H Solar Evaporation Basins

Groundwater monitoring at the 183-H Solar Evaporation Basins is regulated under Washington Administrative Code 173-303-645. Proposed in this plan is the first phase of a final-status, corrective action monitoring program for the site. The monitoring network consists of four existing wells: 199-H4-3, 199-H4-7, 199-H4-12A, and 199-H4-12C. Well 199-H4-12C is completed at the base of the unconfined aquifer; the other wells are screened at the water table. Wells 199-H4-7 and 199-H4-12A are groundwater extraction wells used in a pump-and-treat system. Groundwater samples will be collected from each well annually. Samples will be analyzed for the following: (1) constituents of concern (i.e., chromium, nitrate, technetium-99, and uranium) and fluoride; (2) additional constituents to aid data interpretation (e.g., alkalinity, anions, and metals); and (3) field parameters routinely acquired at the wellhead (e.g., pH, specific conductance, temperature, and turbidity). The objective of monitoring during operation of the pump-and-treat system is to determine whether concentrations of the contaminants of concern are decreasing