driven backfill tampers shall be used in areas inaccessible to rollers. Three -wheel rollers shall weigh not less than 10 tons. They shall be o f sturdy construction and especially designed for heavy work. They shall be in good mechanical condition and have sufficient power to travel over rough surfaces and steep grades. Pneumatic tired rollers shall operate on two axles in such manner that the rear group of tires will not follow in the tracks of the forward group. They shall be mounted on a rigid frame and have a loading platform or body suitable for ballast loading. Th e pneumatic tired rollers, under working conditions, shall have a minimum rolling width of sixty ( 60) inches and shall give a minimum compression of 325 lb. per inch of width of tire tread. Single axle pneumatic rollers of an approved type may be used, p roviding the requirements as to width and compression per inch of width of tire tread are met. Tamping rollers shall consist of metal rollers, drums, or shells surmounted by metal studs with self -cleaning tamping feet. The cross sectional area and spaci ng of tamping feet and the weight of the roller shall be such that the compaction or density for the particular material shall be obtained as specified. Each tamping roller shall consist of at least two sections not rigidly joined. Grid rollers shall co nsist of drums at least five ( 5) feet in diameter whose cylindrical faces present the appearance of an open woven bar mesh. Each drum shall be at least 2 -1/2 foot long and they shall be independently mounted close together on the same axle. The complete roller, when operating without ballast, shall weigh not less than six tons or 200 lb. per in ch of length of roller drum. Arrangements shall be provided for adding ballast, as directed by the Engineer, to such an extent that the total weight of the unit c an be increased to at least 15 tons and 500 lb. per inch of length of roller drum. Grid rollers shall make at least three complete coverages of each layer or until the required density is obtained. The use of trucks, carryalls, scrapers, tractors, tract or wagons, or other haulage equipment shall not be considered in lieu of compacting equipment prescribed, but the traffic of such hauling equipment shall be distributed over the fill in such a manner as to make use of the compaction afforded as an addition to compaction by rolling or vibrating.
207.8 -FINISHING EARTH ROADS : When no pavement or surfacing is included in the Contract, the roadway shall be finished as a graded earth road. The roadw ay, shoulders, and superelevated curves shall be constructed simultaneously to the required cross section and grade. Unsatisfactory or unsuitable material shall be removed and replaced as specified in Subsection 207.9. The entire surface shall be brought to a smooth condition by repeated use of an approved power grader and continuously maintained in a condition suitable for traffic until final completion and acceptance of the work. When grading work is being done simultaneously on more than one section o f a Contract, an approved grader shall be furnished on each section if so required by the Engineer.
207.9 -SUBGRADE : The subgrade shall be constructed in accordance with these Specifications, in substantial conformity with lines, grades, and cross sections shown on the Plans or established by the Engineer. The subgrade shall be six ( 6) inches compacted thickness for all embankment and excavation sections and shall be constructed out of suitable material free of particles larger than three ( 3) inches and consisting of granular material, conforming to the requirements of Subsection
122 716.1.1.2, that can be satisfactorily com pacted to a stable condition. The tolerance set forth in not be paid for, except, when unsuitable material is removed as specified below, payment will be made for removal to an additional depth of twelve ( 12) inches of this unsuitable material with the actual locations and depth of removal established by or acceptable to the Engineer. The subgrade layer or layers shall be moistened or dried to a uniform mois ture content suitable for maximum compaction and brought to a firm unyielding condition by compaction. The subgrade shall be uniformly compacted to the applicable requirements specified in 716. Reclaimed asphalt pavement (RAP) may be used for subgrade. The top size of gradation shall not exceed three ( 3) inches and shall be placed in accordance with Sections 207 and 716.2. Approval for gradation shall be by visual inspection by the Engineer. The surface of the subgrade shall be maintained in such condition that it will drain at all times. When trenching is done for narrow base widening, ditches of an adequate depth shall be constructed across the shoulders at sufficient intervals to permit a free outlet of water. Equipment or vehicles shall not be all owed to travel in a single track and form ruts in the subgrade. Any ruts or irregularities formed in the subgrade shall be scarified and recompacted. When the construction of a base, pavement, or surface is included in the Contract, or is so provided on the Plans, the profile grade of the subgrade shall be such that the specified thickness of the base course, pavement and surface will be obtained within limits of final surface grade. Any grade revision necessitated shall be called to the atte ntion of the Engineer. When unsuitable material is encountered at the subgrade elevation, it shall be removed to a depth of twelve ( 12) inches and replaced with suitable material. When so designated, engineering fabric for subgrade stabilization, conforming to 715.11, shall be installed over the area which shall be relatively smooth, free of sharp protrusion, depressions or debris. The fabric shall be placed with the machine direction of the fabric parallel with the alignment and shall be relatively smoo th and free from creases. The joining of fabrics shall be accomplished by sewing (either in the field by portable sewing machine or during manufacture of the fabric) as outlined in 715.11.3 or shall be installed so any splice joints have a minimum overlap of three ( 3) feet or as directed by the Engineer. Once the fabric is placed, cover material shall be brought to the working face, dumped and spread with equipment exerting the minimum ground pressure possible. Construction equipment shall not operate directly on the fabric. A minimum of six (6) inches of cover material shall be maintained between the construction equipment and the fabric. Compaction shall be accomplished by conventional methods after the cover material is spread. Sheepsfoot rollers will not be permitted. The completed subgrade shall present a uniform appearance and shall be checked for conformity to the lines, grades, and dimensions shown on the Plans. When the Plans require engineering fabric for subsurface drainage or sep aration, the material shall conform to subsection 715.11 and be placed as fabric for stabilization except the fabric may be joined by overlapping so the splice joints have a two foot minimum overlap. Construction equipment is permitted on the fabric provi ded all damage is repaired as specified in subsection 715.11.3. When the fabric is placed in structure backfill applications, such as bridge abutments, the orientation of the fabric will be directed by the Engineer.
207.9.1 -Tolerance: The completed su rface shall not vary more than ½ inch above or below plan grade. Deviations shall be corrected by scarifying, adding additional approved aggregate if necessary, and recompacting.