Smelter slag containing copper and other trace elements is widespread in riverbed sediment of the upper Columbia River (UCR) of the United States. To evaluate potential risk to aquatic life concentrations of copper and other trace elements were measured in shallow pore-water and in river water samples collected near the sediment-water interface. Samples were collected using an in-situ pore-water profiler to collect a suite of four water samples from above, at, and below the sediment-water interface at each of 29 sampling locations; pore-water collected with a drive-point sampler at 10 additional locations; and Stabilized Liquid Membrane Device samplers (SLMDs) to allow determination of trace-element concentrations directly at the sediment-water interface at 8 locations. Samples were collected between April 26 and August 5, 2015 from a total of 47 locations in the UCR between river-mile 715 and 745. The analysis of water samples included specific conductance, pH, alkalinity, fluoride, chloride, bromide, nitrate, sulfate, phosphate, dissolved organic carbon, silver, aluminum, arsenic, barium, beryllium, bismuth, calcium, cadmium, cerium, cobalt, chromium, cesium, copper, dysprosium, erbium, europium, iron, gallium, gadolinium, germanium, holmium, potassium, lanthanum, lithium, lutetium, magnesium, manganese, molybdenum, sodium, niobium, neodymium, nickel, phosphorus, lead, praseodymium, rubidium, antimony, scandium, selenium, silica, samarium, strontium, tantalum, terbium, thorium, titanium, thallium, thulium, uranium, vanadium, tungsten, yttrium, ytterbium, and zinc. The analysis of SLMD samples included cadmium, copper, nickel, phosphorous, and zinc.