§ 11-123. Subgrade.

(a)

In fill sections where A-5, A-6, or A-7 soils are encountered which have an LL greater than 40 or a PI greater than 17, an upgraded embankment material should be used in the top two (2) feet of the subgrade; or the top six (6) inches of the subgrade treated with lime. In cut sections where A-5, A-6 or A-7 soils are encountered which have a LL greater than 40 or a PI greater than 17, the top (6) inches of the subgrade should be treated with lime. These requirements are in addition to the pavement section required based upon the soil type of the existing subgrade material.

(b)

When lime treatment is required, the subgrade shall be finished to stringline grade prior to adding and mixing the lime. The depth of the lime treatment shall be checked at 500-foot intervals. The depth of the lime treatment shall be at least five and one-half (5½) inches. If the depth is less than five and one-half (5½) inches, the section represented by the test shall have additional lime added and the section reprocessed.

(c)

The subgrade shall be prepared in such a manner to ensure a firm foundation that is stable and free from dust pockets, wheel ruts and other defects.

(d)

The top eight (8) inches of the subgrade shall be compacted to a density, as determined by AASHTO T 191 or T 238, of not less than ninety-five (95) percent of the maximum density obtained by AASHTO T 99. This shall be accomplished by scarifying as necessary, shaping and compacting to the required grade and section at near optimum moisture content.

(e)

The finished subgrade shall be stringlined within ¾ inch of the finished grade and typical section shown on the approved plans.

(Ord. No. 91-9, Art. 1, § 4.04, 4-11-91; Ord. No. 99-32, Art. 1, 7-8-99)