§ 54-66. Minimum public road standards.

(a)

Grading plan. A grading plan for the entire site shall be submitted as part of the design plan.

(b)

Subgrade. All testing shall be performed by a qualified, independent, pre-approved testing firm. The owner or contractor shall be responsible for coordinating the testing and notifying the county subdivision inspector as to the scheduled testing time. A county subdivision inspector shall be present for all testing.

Borrow material to be used for soil fill will be collected and tested for maximum dry density and optimum moisture content (standard Proctor ASTM D698) prior to commencement of fill placement activities.

Fill soils will be compacted in thin layers of no more than eight inches by sheepsfoot compactor or other equipment approved by the county. All fill soils shall be compacted to a minimum of 98 percent standard Proctor maximum dry density and within plus or minus three percent of optimum moisture content. Six density tests should be performed no less than every 10,000 square feet of area per 8-inch lift (approximately one test every 50 feet).

Soils in fill areas prior to fill placement and soils at finished subgrade elevation in both cut and fill areas should be proofrolled. Proofrolling shall be performed under the observation of the county subdivision inspector and, if possible, a testing firm representative.

The subgrade shall be prepared with a four-inch crown and graded within one half-inch plus or minus of the centerline profile grade.

(c)

Base course. The county subdivision inspector shall be notified when the base course is to be placed. The base course shall consist of eight inches of compacted crushed stone on all local/residential streets. The base stone shall be placed in two lifts to a minimum width of 29 feet. The subdivision inspector shall verify the compacted thickness of the lifts being applied. The base course must be compacted to 95 percent Standard Proctor. The base material must conform to TDOT specifications 303.01 mineral type "A" base grade "D" and shall be prepared through a pug mill. The base stone shall be placed with a suitable mechanical spreader, as approved by Knox County Engineering, capable of spreading the base stone to a uniform thickness.

For commercial streets the base course shall consist of eight inches of compacted crushed stone while for industrial streets it shall consist of ten inches of compacted crushed stone. The conditions in the previous paragraph also apply.

(d)

Asphaltic binder course. The county subdivision inspector shall be notified prior to the placement of the asphaltic binder course. The asphaltic binder course, grade "B" modified, shall consist of two and one half inches of compacted mix that conforms to TDOT specifications for 307.01 and 307.02 and also under subsection 903.06. The asphaltic binder course shall have a minimum width of 28 feet. The mix must be rolled and compacted with a suitable roller and shall be subject to approval by Knox County Engineering. An average of 92 percent of theoretical density shall be required. No individual density test shall be less than 90 percent of theoretical density. The county subdivision inspector shall inspect and approve the work as it is performed.

For commercial streets the thickness of the binder shall be three inches. For industrial streets the thickness shall consist of three inches of A-S Mix and two inches of "B" modified. The conditions of the previous paragraph also apply.

(e)

Curbs. Concrete curbs shall be placed on the binder mix. Concrete curbs shall be eight inch extruded curbs that have a compressive strength of 3000 psi.

(f)

Asphaltic surface course. The county subdivision inspector shall be notified when the asphaltic surface course is to be placed. The asphaltic concrete course, grade "E", shall consist of one and one half inches of compacted mix. The asphaltic concrete course must conform to TDOT specifications for 411.02.01 and 411.02.92, 411-E gradation and subsection 903.11. "D" mix is required whenever a grade exceeds 10 percent anywhere within the subdivision. The mix shall be rolled and compacted with a suitable roller and will be subject to approval by Knox County Engineering. A subdivision inspector shall be present to approve the work as it is performed.

For commercial streets the required thickness of asphaltic surface course shall be two inches. For industrial streets the required thickness of asphaltic surface course shall be two inches. The conditions of the previous paragraph also apply.

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STREET TYPE	BASE THICKNESS	BINDER THICKNESS	SURFACE THICKNESS
Local	8 inches	2-½ inches "B" Mod.	1-½ inches
Commercial	8 inches	3 inches "B" Mod.	2 inches
Industrial	10 inches	3 inches A-S and 2 inches "B" Mod.	2 inches

 

(Ord. No. O-01-2-101, § 1, 3-26-01)