I'm not sure about the increase since 2000 (could be better detection methods), but the military is known to use a bunch of toxic chemicals. On the motorcycle forums I frequent I have heard more than a few times about how "The stuff we had when I was in the Army/Navy/AF would have cleaned this up in seconds." And they were only talking about the degreasers and lubricants, not the munitions or other chemicals that were hanging around the base.
Read about Agent Orange if you want to be pissed off for the rest of the day: https://en.wikipedia.org/wiki/Agent_Orange#U.S._veterans