A cargo container is modified to carry a fracing proppant such as sand from a quarry or source to the frac site. Openings are cut in the top and bottom of a cargo container and hydraulically operated sliding doors are placed there under. A hopper module with the walls being inclined to approximately the angle of repose for the proppant is installed inside the cargo container. The hopper module is sealed inside the cargo container so that a proppant enters through the top opening at the quarry and flows out through the bottom opening at the fracing site. Once transported to the frac site, the modified cargo container is lifted, emptied and set aside.