Root cellar footers - building off grid // E131

We are in the process of building an office and decided a root cellar beneath it would be an invaluable addition to our homestead. Our house site is off grid and will include a solar powered electric system, which the office structure will house for us. Our root cellar will be used for long term food storage and a water holding tank that will supply our house. It will also double as an emergency location for our family in case we get in the path of a torrential storm or tornado. The start of this root cellar/office combo begins with the pouring of concrete footers. We use our own sawmilled lumber for the form boards and battle against all the rocky terrain to get our footers poured.