I emailed the reporter that wrote the story I followed from the link below. 

My email:

"I read about the article on a farm site.  Many people were curious if anybody was concerned about the man that was rescued. The stories all seem to imply that the major concern was some silt and that was released into the river. 

In addition many wondered what type of machine could sustain air sufficient to sustain life and not fill with water over the 2 ½ hours. 
If you have access to the information regarding the machine, the condition of the rescued man and have time, could you please reply?" 

 I received a reply rather quickly:
 

I think there was a great deal of concern for Mr. Gunderson. The whole reason they drained the pond was to rescue him. 
He was not injured and I'm told is "doing fine," as the story said. I'm told he was operating a Cat D6T. I don't know if the cab is designed to be air-tight for all situations or if it was able to hold because of the viscosity of the material.