The way I see it is that as long as civilians lives and security are not jeopardized in any way by the efforts of the military training, then it stands to reason that this training poses no unreasonable threat for which to deny them this vital training. Do it if it is necessary.
In the same way sportsmen prepare for matches by using dummy matches, the military should be allowed to have their exercises. This helps the soldiers sharpen their skill in readiness for war. It also gives them the opportunity to have a glimpse of what they can expect in war fields since they cannot practice during real wars.
It is bizarre that this is a debatable question. Whatever prepares our military best for defending our nation should always be allowed. Thankfully our military has experts in every field, including all sorts of safety officers, whose sole job is keeping civilians (and soldiers) safe, so the people in Bastrop county have nothing to worry about.
The 19th century Posse Comitatus Act forbides the US military from exercising on US soil. The premise of this act is that the military is an external force to be used against external enemies; it should under no circumstances be turned inward against US citizens. Jade Helm is a traducment of US sovereign citizenship by its government.