29 CFR 1926.958 - Materials handling and storage.
(a)General. Materials handling and storage shall comply with applicable material-handling and material-storage requirements in this part, including those in subparts N and CC of this part.
(b)Materials storage near energized lines or equipment -
(1)Unrestricted areas. In areas to which access is not restricted to qualified persons only, materials or equipment may not be stored closer to energized lines or exposed energized parts of equipment than the following distances, plus a distance that provides for the maximum sag and side swing of all conductors and for the height and movement of material-handling equipment:
Paragraph (b) of § 1926.966 specifies the size of the working space.