35 Ill. Adm. Code 811.305
Foundation Construction
Section 811
Section 811.305 Foundation
Construction
a) If the in situ material provides insufficient strength to meet
the requirements of Section 811.304, then the insufficient material shall be
removed and replaced with clean material sufficient to meet the requirements of
Section 811.304.
b) All trees, stumps, roots, boulders and debris shall be
removed.
c) All material shall be compacted to achieve the strength and
density properties necessary to demonstrate compliance with this Part in
conformance with a construction quality assurance plan pursuant to Subpart E.
d) Placement of frozen soil or soil into frozen ground is
prohibited.
e) The foundation shall be constructed and graded to provide a
smooth, workable surface on which to construct the liner.