Limited field investigation report for the 100-BC-5 Operable Unit

This limited field investigation (LFI) was conducted to assess the applicability of interim remedial measures (IRM) for reducing human health and environmental risks within the 100-BC-5 Groundwater Operable Unit. The 100-BC-5 Operable Unit is one of three operable units associated with the 100 B/C Area. Operable units 1 and 2 address contaminant sources while 100-BC-5 addresses contamination present in the underlying groundwater. The primary method of investigation used during this LFI was the installation of monitoring wells. Samples were collected from the groundwater and soils and submitted for laboratory analysis. Boreholes were surveyed for radiological contamination using downhole geophysical techniques to further delineate the locations and levels of contaminants. All samples were screened to ascertain the presence of volatile organic compounds and radionuclides. Analytical data were subjected to validation; all first round and 10% of the subsequent rounds of data associated with the LFI were validated. The screening method was used to identify contaminants of potential concern (COPC). This screening method eliminated from further consideration constituents that were below background. Constituents considered nontoxic to humans were eliminated from the human health evaluation. Inconsistency and blank contamination were also evaluated in the screening process. These COPC were evaluated further in the qualitative risk assessment (QRA). Tritium and strontium-90 were identified as contaminants of concern at 100-BC-5 because the concentrations exceeded potential applicable or relevant and appropriate requirements. The QRA determined that the risk is low for all of the site contaminants