(A) All subgrades shall be properly graded to the lines and grades shown on the plans for the given project.
(B) In areas to be cut below existing grade, the Contractor responsible for rough grading shall take the following steps in an effort to obtain less than ninety-five percent (95%) of the standard laboratory density in the subgrade.
(1) The subgrade shall be cleared of all unsuitable material, including, but not limited to, vegetation, tree stumps and roots, trash, debris, soft
spongy soil, etc., for a minimum depth of eighteen (18) inches below subgrade elevation.
(2) Plan ditches that drain the area are to be cut to grade at least two (2) weeks prior to the work required in the following paragraph.
(3) The top eight (8) inches of subgrade shall be air dried and shall include processing the soil utilizing discs or tillers to a depth of eight (8) inches at least twice each day for three (3) consecutive good drying days.
(4) All areas processed per the above paragraph shall be recompacted in order to achieve not less than ninety-five percent (95%) density, or until at least nine (9) passes have been made utilizing a roller that has demonstrated its ability to obtain the required density on adjacent earthwork.
(C) In areas requiring the construction of roadway embankment, and where said embankment will be less than one and one-half (1 ½) feet in height, all filling shall be done in lifts that do not exceed eight inches loose thickness, and that are compacted to not less than ninety-five percent (95%) of the standard laboratory density.
(1) If the embankment height is between one and one-half (1 ½) feet and three (3) feet inclusive, the first lift shall be compacted to not less than ninety percent (90%), and the balance to a minimum of ninety- five percent (95%) of the standard laboratory density.
(2) If the embankment exceeds three (3) feet in height, the lower one- third (1/3) of the embankment, but not more than two (2) feet, shall be compacted in a manner that will yield a minimum of ninety percent (90%) of standard laboratory density to the uppermost lift of that portion of the embankment. The next one (1) foot of embankment shall be compacted to not less than ninety-three percent (93%), and the balance of the embankment compacted to not less than ninety-five (95%) of the standard laboratory density.
(3) Large clods and excessively wet material used for fills shall be disked or raked prior to placement.
(4) No wood, trash, or other objectionable material shall be used for fills.
(D) The standard laboratory density shall be the maximum density determined according to AASHTO T 99 (Method A or C). A coarse particle correction according to AASHTO T 224 shall be used with Method A and may be used with Method C.
(E) The top two (2) feet of all embankments shall not contain more than one hundred twenty percent (120%) of the optimum moisture determined according to AASHTO T 99 (Method C).
(F) Compaction shall be achieved with a roller capable of properly compacting the given type of embankment material; in the case of fine-grained soils, a sheeps-foot roller shall be deemed suitable.