If not used immediately, the darkened surface soil or its equivalent as approved by the Department and the root medium if the root medium is stockpiled in accordance with Section 1825.12 shall be stockpiled separately and these materials shall be stockpiled separately from other spoil, and provided needed protection from wind and water erosion or contamination by acid or toxic or non-soilmaterial. Signs shall lbe erected to indicate the contents of each stockpile.
Ill. Admin. Code tit. 62, § 1825.13