[en] Geophysical investigations using ground-penetrating radar (GPR) and electromagnetic induction (EMI) were conducted at two waste sites, 120-KE-3 and 118-K-2, in the 100-K Area (Figure 1). Both of the sites are located within Operable Unit 100-KR-2. The 120-KE-3 waste site (Figure 2), also known as the 183-Filter Water Facility Trench and 100-KE-3, received sulfuric acid sludge from sulfuric acid storage tanks that were contaminated with 700 kg of mercury. The trench is documented as 3 ft wide by 3 ft deep by 40 ft long. However, part or all of the trench was excavated when an outside contractor attempted to recover the mercury (Carpenter and Cote 1994). Therefore, the actual size of the ''disturbed area'' from the trench and subsequent excavation is unknown. The objective of the geophysical investigation was to locate the original or reworked trench. The 118- K-2 site (Figure 3) was reportedly used to dispose radioactive sludge from the 116-KE-4 and 116-KW-3 retention basins. The size of the ''trench'' is unknown and documentation shows it in two different locations. No other information si available on the site. The objective of the investigation was to locate the trench