No, the military doesn’t dump toxic waste into the ground water. What happens is the waste has been improperly stored or neglected and has leached into the surrounding environment. It’s more a matter of ignorance and carelessness. Add to the fact that a lot of military facilities were built in remote areas far away from populated areas which later saw an establishment of towns some of which eventually grew into cities. All of this was long before Nixon established the EPA and people started to become aware of how toxic some of these sites were. On a good day you can see the condensation plume from the Hanford Nuclear Facility from my house. Hanford was a major player in the Manhattan Project which developed the “atomic bombs”. That place was built in the high desert, miles away from any civilian population and none were allowed to be built nearby. Now Hanford was run by whole lot of really intelligent people who still, in their ignorance treated their highly radioactive and toxic materials in a casual manner.
Really smart lab assistant: “Hey Doc, what should I do with this stuff you told me to get rid of?”
Highly intelligent nuclear physicist: “Oh heck, we’re miles away from anywhere. Just find a remote area of the desert and bury it.”
We’re still in the process of cleaning up Hanford and will be for quite a while. Just this last year they dug up a container which held a number of vials of highly toxic plutonium crystals.