I have an area thats about 3/4 to 1 acre of land, a common area, that is surrounded by 6 units. Recently puchased the properties, and it's covered in massive amounts of goat heads, or puncturevines. This spring I plan to steralize, or I know that they are easily smothered by growing sage grass or bunch grass in the area. My question is, how do I get rid of the seeds? The seeds are the spiked little things that get stuck in your shoes, tires, feet, pets feet, everywhere! I've even had some tennants take their dogs to the vet to remove bad ones, and this property has them worse than I've ever seen. Mainly all over the driveways and walkways. I can control the new ones from coming in, but how do I get rid of the old ones? 

I'm not a farmer or land developer of any sort, but I'd begin with hiring someone to remove the existing ones, then go in with some Spectracide and spray like crazy. I've done this to my front yard with success, but your results may vary. Not sure what kind of soil, air, environment goat heads thrive in out in Idaho. 

You can also try using salt water on the vegetation, but this would kill everything it comes into contact with and I'm not sure that is the outcome you're looking for.