A.
Remove vegetation, debris, unsatisfactory soil materials, obstructions, and deleterious materials from ground surface prior to placement of fills. Plow, strip, or break up sloped surfaces steeper than one vertical to four horizontal so that fill material will bond with existing surface.
(1)
When existing ground surface has a density less than that specified, break up ground surface, pulverize, moisture condition to optimum moisture content, and compact to required depth and percentage of maximum density.
B.
Place select fill material to subgrade elevations in maximum eight-inch horizontal lifts. Adjust the moisture content of embankment fill to within 2% of optimum by either air-drying or addition of water prior to compaction. Spread wet embankment fill in eight-inch loose lift and disc to expedite air drying. Remove rock particles larger than four inches.
C.
If on-site soils are not available, a well-graded bank-run gravel shall be imported.
D.
Compact embankment fill to or above 95% "'Modified Proctor" maximum density with a smooth drum roller, or other sufficient compaction equipment, weighing at least seven tons and operating in the vibratory mode.
E.
Slope the subgrade as shown on Figure No. 1, Typical Highway Cross-Section.[1] Proof-roll the final subgrade to avoid ponding of surface water. Proof-rolling shall be accomplished with a smooth drum roller weighing at least 30 tons and operating in the vibratory mode. Any settlement or movement of the subgrade ahead of or under the roller that indicates a potential soft area will require removal and replacement with suitable compacted granular material.
[1]
Editor's Note: Figure No. 1 is included as an attachment to this chapter.