the naval support activity expanded its mission and department of defense support role over time with over 40 tenant commands, and today is a training center, with the naval nuclear power training command (nnptc), nuclear power training unit, propulsion facility, and border patrol satellite academy; naval consolidated brig, charleston; navy munitions command unit charleston; explosive ordnance detachments; marine corps reserve center; space and naval warfare systems center engineering complex (spawar, the largest employer in the charleston area); 269 above-ground ammunition magazines, maintenance and storage of military ordnance including mines, and serves as an army logistics hub, the busiest continental united states surface port in the defense transportation system. in addition, it contains more than 1,800 on-base houses for navy enlisted and officer dependents as well as coast guard dependents, and has a child care facility, elementary and middle schools. a large medical clinic near nnptc in goose creek was added in 2008.