Abstract: A cover for protecting a pile or mound of particulate material in outside storage so that the material is not contaminated, eroded, dissolved or dispersed by the weather. The cover is provided by a plurality of elongated panels that are connected together along their side edges by seams so that the panels and seams extend perpendicularly from the perimeter of the base of the pile toward the top or apex thereof. Some of the panels of the cover are of a material that is porous to gas and nonporous to liquids, and other of the panels are of a material that is nonporous to both gas and liquids. The different porosity panels are arranged in alternating relation in the cover. The seams are reinforced by strips of reinforcing material sewn thereto. Supplemental lengths of weight retaining strips are secured to some of the perpendicularly extending seams at points spaced upwardly from the margin of the cover.