Cal. Public Resources Code § 4437

(a) Outside the exterior boundaries of cities, every processor of forest products shall exercise due diligence in the disposal of flammable material incident to the processing, so that the material does not cause the inception or spread of uncontrolled fire. (b) Every person, copartnership, firm, corporation, or company that operates a sawmill or plant engaged in the processing or converting of forest products into lumber, shook, ties, poles, posts, veneer, shakes, shingles, and planed or milled products, shall dispose of flammable material incident to that operation. If such flammable material is not to be used as fuel, or as a byproduct, within the operation, it shall be disposed of by burning or by other alternative methods which effectively prevent the flammable material from constituting a fire hazard. The disposal or storage of flammable waste material or residue shall be made in any of the ways which are prescribed in Section 4438, 4439, or 4440. (c) The director may establish regulations for the storage, disposal, or use of forest product waste or residue on land as a soil amendment or soil protection measure or for its disposal by fire. Regulations shall be adopted by the director in accordance with the provisions of Chapter 3.5 (commencing with Section 11340) of Part 1 of Division 3 of Title 2 of the Government Code for the purpose of eliminating the potential of fire resulting from spontaneous combustion, other ignition sources, or wildfire escaping the forest product waste or residue storage, use, or disposal areas.