For a long time NWS Charleston has had a roster of Navy-owned equipment operating over these Navy-owned tracks. Most locomotives have been 65- and 80-ton GE centercabs, although there have been others, such as USN 65-00626, an Alco S1 built in 1943, and USN 65-00132, a Baldwin VO1000 (which I believe has been rebuilt with EMD under the hood). There used to be an enginehouse on base, but by the summer of 2003 it had a sign reading "Condemned" and later it was torn down. It stood near the intersection of Red Bank Road and Sandlapper Lane on the NWS. When I was last there in September, 65-00132 was there, along with a GE centercab sitting where the enginehouse once stood, and I suspect the latter was out of service and has been for a long time. Unfortunately most of the base's tracks lie within the restricted area and I believe most of the locomotives are there as well, so you'll only see them on the rare occasions when they venture forth beyond the fence. If you visit the Public Works office on base, they should be able to tell you more about the locomotives and the operation of the rail line.
There's also a line that goes out to a former munitions storage area on Pomplant Access Road. This used to be a restricted area and possibly still is, but you can view it from above to your heart's content in Google Earth.
