Standards for Root Collar Excavations & Aeration 

A discussion about different RCX/aeration scenarios and how to deal with them.
In the video you will also note that Basil talks about aerating to 3 times the DBH (diameter at breast height) - the rule for the first 3 examples is 3 times DBH OR 3 feet, whichever is larger. on the final example (the bowl), the bowl is only taken out to 3 times the DBH.