§ 58-64. Base course.

(a)

Placement and density. The base course and surfacing of roads shall be placed on a firm foundation that is thoroughly stable. The top six inches of the subgrade shall be compacted to a density not less than 95 percent of the maximum density obtained by the Standard Method of Test for the Compaction and Density of Soils, AASHO designation T-99. Areas of soft unsuitable material shall be completely excavated and replaced with good embankment material.

(b)

Compaction, gradation and shaping requirements. The base course shall be either gravel or crushed stone. The base course may be deleted for portions of a road where the subgrade meets the requirements as follows for compaction, gradation and shaping:

(1)

Construction methods. The base course material shall be placed on a completed and approved subgrade that has been bladed smooth and uniform and conforming to the typical section. Base course material shall not be placed on a frozen subgrade. The base course shall be placed on the subgrade and spread uniformly to such depth and lines so that when compacted it will have the thickness, width and cross section shown on the plans. When the compacted depth of the base course as shown on the typical section exceeds six inches, the material shall be placed in two or more courses of approximately equal depths. No course shall exceed six inches in compacted thickness.

(2)

Gravel. This material shall consist of a natural or artificial mixture of gravel and soil mortar uniformly well graded from coarse to fine. The gravel shall consist of crushed or uncrushed hard pebbles or crushed boulders, and the material shall be reasonably free from objectionable or injurious matter. The grading of the material shall conform as closely as is deemed feasible to GB2 or GB3, Standard Specifications for Highway Construction, state highway commission, edition of 1978.

(3)

Crushed stone. This material shall consist of crusher run stone or a mixture of crushed stone and soil mortar uniformly mixed. The stone shall be hard and durable and the mixture shall be free from objectionable, injurious matter. The grading of the material shall conform as closely as is deemed feasible to class SB-2, Standard Specifications for Highway Construction, state highway commission, edition of 1978.

(4)

Density. Each course shall be compacted by any satisfactory method that will obtain a density of 95 percent of a laboratory run Proctor density test on the material.

(Code 1993, § 58-64; Ord. No. 86-4, art. II, § A(7), (8), 3-13-1986)