Section 02232 PREPARATION OF PAVEMENT SUBGRADE

Section 02232

_{PREPARATION OF PAVEMENT SUBGRADE}

PART 1 - GENERAL

1.1 THE REQUIREMENT

A. The CONTRACTOR shall furnish all tools, equipment, materials, and supplies and shall perform all labor required to complete the work of preparation of subgrade requirements as indicated on the Drawings and specified herein.

B. The subgrade will be considered as those areas and surfaces, new or existing, upon which subbase or base material, pavement, curbs and gutters, driveways, or sidewalks are to be placed.

C. All underground work in the area of the subgrade shall be completed, properly backfilled and compacted in compliance with the Geotechnical Study Report prepared by Converse Consultants, and Section 02200, Earthwork, before subgrade work is started.

1.2 RELATED WORK SPECIFIED ELSEWHERE

A. The requirements of the following Specification sections and divisions apply to the Work of this section. Other sections and divisions of the Specifications, not referenced below, shall also apply to the extent required for proper performance of this Work.

1. Section 02050, Demolition

2. Section 02110, Clearing, Grubbing, and Stripping

3. Section 02200, Earthwork

4. Section 02527, Concrete Curbs and Sidewalks

5. Section 02550, Asphalt Concrete Pavement

1.3 REFERENCE SPECIFICATIONS, CODES, AND STANDARDS

A. All Work specified herein shall conform to or exceed the applicable requirements of the referenced portions of the following publications to the extent that the provisions thereof are not in conflict with other provisions of these Specifications.

B. Comply with the applicable editions of the following codes, regulations and standards.

1. Industry Standards:

ASTM D 1557 Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Modified Effort (56,000 ft-lbf/ft3 (2,700 kN- m/m3))

SSPWC Subsection 301-1 “Green Book”, Standard Specifications for Public Works Construction, Subgrade Preparation

C. Comply with the applicable reference Specifications as directed in the General

Requirements and the Additional General Requirements.

1.4 CONTRACTOR SUBMITTALS

A. Submittals shall be made in accordance with the General Requirements, Additional

General Requirements and as specified herein.

1.5 QUALITY ASSURANCE A. General

1. Quality assurance shall be as specified in Section 02200, Earthwork.

1.6 WARRANTY

A. Guarantees and Warranty shall be furnished in accordance with “Warranty” (CONTRACTOR’s Guarantee) of the General Conditions.

PART 2 - PRODUCTS

2.1 EXCAVATION AND EMBANKMENT

A. The excavation shall include removal of materials that are encountered in excavating to the required grades as shown on the Drawings, including existing pavement, sidewalks and curbs designated to be removed, or other deleterious materials as required to accomplish the construction.

B. Unsuitable material below the processing depth for subgrade shall be excavated and disposed of specified in Section 02200, Earthwork, or as directed by the ENGINEER.

PART 3 - EXECUTION

3.1 SUBGRADE

A. Excavate and shape subgrade to line, grade, and cross-section shown on the Drawings. Scarify and compact the top 3 (three) feet of subgrade to at least 95 percent of the maximum dry density attainable as determined by ASTM D 1557 except clay soils with a Liquid Limit greater than or equal to 50 percent and a plasticity index greater than or equal to 20 shall be prepared according to the recommendation of the ENGINEER. The upper 1 (one) foot of subgrade soils should be compacted to at least 95 percent of the laboratory maximum dry density. Remove all soft or otherwise unsuitable material and replace with suitable material as specified in Section 02200, Earthwork. In sandy soils the moisture content shall be kept at or slightly above the optimum moisture content. However, in clayey and silty soils, the moisture content shall be kept at about 2 percent above the optimum moisture content. The finished subgrade shall be firm, hard, and unyielding. The subgrade shall be considered to extend over the full width of the base course. Compaction shall extend a minimum of 2 (two) feet beyond the edge of paving, curb, or form.

B. Subgrade tolerances for roadway structures, sidewalk, curb and gutter, and driveways shall be in conformance with SSPWC Section 301-1.4.

3.2 EXCAVATION BELOW SUBGRADE

A. Where the ENGINEER determines the subgrade material to be unsuitable, excavation below subgrade will be required to such depths as necessary to remove the unsuitable material. Special equipment may be required because of the presence of shallow utilities or other unforeseen conditions.

B. The over excavated unsuitable subgrade shall be replaced with suitable material per

Section 02200, Earthwork.

3.3 PROTECTION OF SUBGRADE

A. After preparing the subgrade as specified, all traffic on the subgrade shall be avoided prior to paving. Should it be necessary to haul over the prepared subgrade, the CONTRACTOR shall drag and roll the traveled way as frequently as may be necessary to remove ruts, cuts, and breaks in the surface. All cuts, ruts, and breaks in the surface of the subgrade that are not removed by the above operations shall be raked and hand tamped. All equipment used for transporting materials over the prepared subgrade shall be equipped with pneumatic tires.

B. Continued use of sections of prepared subgrade for hauling that cause it to be cut up or deform it from the true cross-section will not be permitted. The CONTRACTOR shall protect the prepared subgrade from all traffic.

C. The CONTRACTOR will be required to plank the subgrade before hauling materials or equipment over it.

D. The subgrade shall be maintained in the finished condition as required by Article entitled “SUBGRADE” of this Specification until the first succeeding course is placed.