92. If all or part of a trench landfill is temporarily closed for a period of 3 months or more, and subject to the second paragraph, the residual materials deposited in a trench must be covered with at least 30 cm of soil at the latest by the expiry of the third month.
Any trench that is unused for a period of 6 months must be filled in as provided in section 91 at the latest by the expiry of the sixth month.