R 299.4913 Landfill construction; compacted soil liners and final covers.

Rule 913. (1) A compacted soil liner shall be constructed to have a saturated, vertically oriented hydraulic conductivity of not more than 1.0 x 10-7 centimeters per second after compaction. (2) To meet the hydraulic conductivity standard specified in subrule (1) of this rule, the owner and operator shall assure that the soil source is in compliance with both of the following requirements: (a) Has a classification of SC, CH, CL, CL/ML or ML as determined by the unified soil classification system, ASTM standard D2487-93, unless another classification has been approved as part of a modified soil approved by the director under subrule (3) of this rule. (b) Has a laboratory hydraulic conductivity that is equal to or less than 1.0 x 10-7 centimeters per second within the density and moisture content range specified for construction as determined by a laboratory study of the relationship between moisture, density, and the hydraulic conductivity of the soil. (3) The owner and operator of a landfill may use a soil type other than that specified in subrule (2)(a) of this rule if the soil type is used as a component in a modified soil that is prepared in accordance with a plan approved by the director. The director shall approve a plan for a modified soil if the applicant demonstrates, by laboratory methods or a test pad, all of the following: (a) The modified soil can be compacted to achieve the hydraulic conductivity specified in subrule (2)(b) of this rule. (b) Engineering properties of the modified soil are equivalent to those soil types approved in subrule (2) of this rule. (c) The modified soil will be mixed in a manner that assures consistent properties. (4) The owner and operator of a landfill shall construct a compacted soil liner and final cover in a manner that satisfies all of the following requirements for each lift being compacted: (a) The lift thickness is generally not more than 6 inches after compaction. (b) Each lift is thoroughly and uniformly compacted to that density, and at that moisture content, determined necessary to achieve the required hydraulic conductivity. However, soil shall not be compacted at moisture contents that are less than optimum and shall not be compacted to less than 1 of the following: (i) 90% of the maximum dry density, as determined by the modified proctor test, ASTM D1557-91. (ii) 95% of the maximum dry density, as determined by the standard proctor test, ASTM D698-91. (c) Each lift is integrated into the previous lift by techniques such as scarifying each lift and by using compaction equipment that is capable of penetrating the thickness of each compacted lift, except that such a compactor shall not be used in the first 2 lifts immediately above the synthetic liner, secondary collection system, or other sensitive liner system component. (d) The liner is constructed so that the bottom liner and sidewall liner or dike will be continuous and completely keyed together at all construction joints. (5) The owner and operator of a landfill shall protect a compacted soil liner and final cover from detrimental climatic effects during construction by doing all of the following to the extent necessary to maintain compliance with these rules: (a) Removing all ice and snow during winter construction before placing a lift and not using frozen soil in any part of a liner. (b) Before the liner is covered by a flexible membrane liner or leachate collection system, recompacting any soil lift that has had its integrity adversely affected by weather. (c) Ensuring that soil liners and final covers are not subject to significant desiccation cracking by doing 1 of the following: (i) Sprinkling the liner with water, as necessary. (ii) Covering or tarping the soil. (iii) Taking other preventative measures. (d) If significant desiccation has occurred, by removing or repairing any soil that has experienced desiccation cracking, as necessary, before compacting the next lift or installing the next liner system component. (6) The owner or operator of a landfill may modify the construction requirements of this rule if he or she demonstrates, to the director or his or her designee, using either of the following methods, that alternate construction techniques will achieve the desired liner permeability: (a) A laboratory method that is approved by the director. (b) A test pad that is in compliance with subrule (7) of this rule. (7) A test pad demonstration shall be in compliance with all of the following provisions: (a) Replicate the proposed liner by having all of the following dimensions: (i) A width that is not less than twice that of the proposed roller. (ii) A length that is not less than twice the width. (iii) A thickness that is not less than 2 feet. (b) Use the same materials and construction practices as those proposed for the landfill liner. (c) Determine the hydraulic conductivity of the test pad using insitu, nondestructive testing. (8) The owner or operator may propose alternate specifications for hydraulic conductivity and compaction in the sidewalls of the top composite liner of a landfill unit that has 2 composite liners and a secondary collection system. The director shall approve alternate specifications if the specifications are sufficient to maintain allowable flow rates in the secondary collection system. (9) ASTM test methods D2487-93, D1557-91, and D698-91 are adopted by reference in R 299.4135.