Also could be that the course was created by a shaddy grading contractor and they buried all the trees under the course instead of hauling them off or chipping them. Sometimes when plant matter decays it builds up gas from the decomposition and makes a bubble like that because of the way sod works. It forms a tight carpet like root system that blocks the gas from escaping unlike normal grass. So what happens is this root system is like a plastic bag on top of an air hose... it balloons up.

Now on the one that is actually in that picture it is liquid in nature for sure because of the way the grass "bounces" back. I would say it's a ruptured sprinkler system instead of a septic because there is no pressure on a septic system unless it's a pump system and it wouldn't be able to cause that kind of ballooning. It would actually come back inside the house before it would ever do anything like that. Path of least resistance and all that.

 

 

 

 

 

One man band...

 

 

Unless that's the leach bed, cause that actually leaves the septic system and is under the grass. But that would be a lot of fluid at one time to build up.

 

 

That's why it looked so familiar...

 

thats called "The Bushmaster". Gets used in college wrestling a lot also.

 

right in the taint!