Oneill Groundwater is a superfund site located at Douglas & 4th Street, O'neill, NE 68763. The Environmental Protection Agency (EPA) identifies sites such as Oneill Groundwater because they pose or had once posed a potential risk to human health and/or the environment due to contamination by one or more hazardous wastes. Oneill Groundwater is currently registered as an Active superfund site by the EPA. However, it is not on the NPL (National Priorities List), which means the EPA does not consider it one of the nation's most hazardous waste sites.