The entire area to be occupied by the roadway plus an
additional four feet or extending outward to the toe of slopes in fill areas,
whichever is greater, shall be excavated a minimum of 15 inches below finished
grade in cut sections or as necessary to remove the topsoil in fill sections
or such greater depth as may be required by the Board's engineer if soft
or yielding material, clay, peat, silt, sand pockets, boulders or rocks, organic
materials, or other material detrimental to the subgrade is encountered. All
fill or undisturbed material shall be non-frost-susceptible and shall contain
not more than 3% passing the No. 200 sieve for a minimum depth of three feet
below the finished roadway grade.
