Fungus Gnats / Help

So I went to Ace hardware a couple weeks ago and bought 4 bags (1 cubic ft each) of organic garden soil for outdoor growing. Each bag had a whole in it, so I was able to get the bags for half off.
However they been in storage for 2 weeks and upon my return in find that fungus gnats have completely colonized my garden soil.
What are some methods to get rid of the fuck heads?

Would it do the trick If I were to lay the infested soil along the bottom 6" of my holes and covered that with 10" of other soil?

H2O2

here have a read:

http://joemacho.hubpages.com/hub/Hydrogen-Peroxide-for-Plants