R 299.4912 Landfill construction; natural soil barrier verification.

Rule 912. (1) A natural soil barrier at a landfill that is used to comply with these rules shall be verified in accordance with this rule. Information collected under this rule shall be submitted to the solid waste control agency with either the hydrogeological report or, for existing disposal areas, the construction certification that is submitted under R 299.4921. (2) An owner or operator shall verify that any natural soil barrier extends to the surface. Natural soil sites where the soil barrier does not extend to the surface shall include compacted side cutoff walls or an equivalent barrier to impede the lateral infiltration of water into the fill and to impede lateral flow of leachate out of the fill interior. The wall or other barrier shall be equivalent in width and permeability as that of the soil barrier required by these rules. Hydraulic head buildup outside the wall shall be limited to the extent necessary to prevent unstable conditions within the wall or liner. The hydraulic head shall be controlled by gravity or, as an alternative, the hydraulic head of groundwater that does not constitute an aquifer may be limited by pumping if the system is part of a sewerage system permitted by the director, or his or her designee, under part 41 of the act. (3) To use a natural soil barrier, the owner and operator shall demonstrate that the natural soil barrier does both of the following: (a) Is in compliance with the thickness and hydraulic conductivity requirements of these rules. To demonstrate this, the owner and operator shall obtain soil borings on the grid spacing specified in subrule (4) of this rule and determine all of the following at various depths: (i) The particle size distribution, by sieve and hydrometer. (ii) The Atterberg limits, according to ASTM D4318-95a, which is adopted by reference in R 299.4135. (iii) The classification pursuant to the unified soil classification system, ASTM D2487- 93, which is adopted by reference in R 299.4135. (iv) The hydraulic conductivity of an undisturbed sample by a method specified in R 299.4920. (b) Provides an adequate subbase for the overlying leachate collection and removal systems by evaluating the subgrade conditions for stability and correcting unstable areas. (4) An owner and operator shall obtain soil borings on a grid spacing approved by the director based on either of the following: (a) The homogeneity of soils at the site, as determined by a hydrogeologic report. (b) Geophysical methods that are proposed under subrule (5) of this rule. (5) An applicant may utilize geophysical methods to replace or supplement borings specified in subrule (4) of this rule if a plan for such a survey is approved by the director or his or her designee.