I used my 4 Piece Ryobi set to build this root cellar. The entire project took just over a month. A high percentage of the time involved collecting the river rock and transporting it to my site. The river rock was then used to line the dug out area of the hill and to use as the foundation of the root cellar. The roof is a Gamble style and was with by 2x4's, cutting the 2x4's in 4' lenths and then cutting the ends at a 22.5 angle and then fitted together with 3' screws to form the gabbles.
The gabbles were attached to the wood walls that are 16'' high and built from 2x6's.
Attached is a picture of the root cellar.