How much (in cubic feet or pounds) of each ingredient will result in 30 cubic feet of gritty mix?

Response from Michael Larkin Garden Design: I have never made that large of a quantity. I purchase the bagged ingredients and then use a 5 gal bucket to measure. 1 bucket equals 1 part. Mix in wheelbarrow.

The formula can be found on the Garden Web Forum, go to the container forum. It is called Al's Gritty Mix. If you are a member of the forum post this question and Al may reply.