Usn Naval Support Facility is a superfund site located at Post Office Box 1000, Thurmont, MD 21788. The Environmental Protection Agency (EPA) identifies sites such as Usn Naval Support Facility 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. Usn Naval Support Facility 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.