02222 Excavation.doc

Base Pavements IDIQ

JCGU 09-1700

DIVISION 2 - SITE WORK

SECTION 02222 - EXCAVATION, TRENCHING,

AND BACKFILLING FOR UTILITIES SYSTEMS

PART 1 – GENERAL:

1.1 REFERENCES: The publications listed below form a part of this specification to the extent referenced. The publications are referred to in the text by basic designation only. All publications shall be the latest version/edition/revision of the documents listed below, in effect on the date of this solicitation, except where a date is given.

American Society of Testing and Materials (ASTM)

ASTM D 422

Particle-Size Analysis of Soils

ASTM D 1556

Density of Soil In Place by the Sand-Cone Method

ASTM D 1557

Moisture-Density Relations of Soils and Soil-Aggregate

Mixtures Using 10-lb.(4.54-kg) Rammer and 18-in.

(457-mm) Drop

ASTM D 2487

Classification of Soils for Engineering Purposes

ASTM D 2922

Density of Soil and Soil-Aggregate In Place by Nuclear Methods (Shallow Depth)

ASTM D 3017

Moisture Content of Soil and Soil-Aggregate

In Place by Nuclear Methods (Shallow Depth)

EM 385-1-1: U.S. Army Corps of Engineers (COE) Safety & Health Requirements Manual

Department of Labor, OSHA Requirements

1.2

DEFINITIONS:

Degree of compaction shall be expressed as a percentage of the maximum density obtained by the test procedure presented in ASTM D1557.

1.3

SUBMITTALS:

The following shall be submitted in accordance with Specification SECTION 01010:

Test Reports:

Copies of all laboratory and field test reports shall be submitted to the Contracting Officer within 24 hours of the completion of the test.

Certificates of Compliance:

Certified copies of test reports demonstrating conformance to paragraph 3.4 shall be delivered to the Contracting Officer before pipe is installed.

Location of Stockpile Area

PART 2 – PRODUCTS:

2.1 MATERIALS:

2.1.1 Satisfactory Materials: Satisfactory materials shall consist of any material classified by ASTM D2487 as GW, GP, SW, SP and SC.

2.1.2 Unsatisfactory Materials: Unsatisfactory materials shall be materials that do not comply with the requirements for satisfactory materials. Unsatisfactory materials include but are not limited to those materials containing roots and other organic matter, trash, debris, frozen materials and stones larger than six inches, and materials classified in ASTM D2487 as PT, OH, and OL. Unsatisfactory materials also include man-made fills, refuse, or backfills from previous construction.

2.1.3 Cohesionless and Cohesive Materials: Cohesionless materials shall include materials classified in ASTM D2487 as GW, GP, SW, and SP. Cohesive materials include materials classified as GC, SC, ML, CL, MH, and CH. Materials classified as GM and SM will be identified as cohesionless only when the fines are nonplastic.

2.1.4 Unyielding Material: Unyielding material shall consist of rock and gravelly soils with stones greater than six inches in any dimension or as defined by the pipe manufacturer, whichever is smaller.

2.1.5 Unstable Material: Unstable material shall consist of materials too wet to properly support the utility pipe, conduit, or appurtenant structure.

2.1.6 Initial Backfill Material: Initial backfill shall consist of select granular material or satisfactory materials free from rocks four inches or larger in any dimension or free from rocks of such size as recommended by the pipe manufacturer, whichever is smaller. When the pipe is coated or wrapped for corrosion protection, the initial backfill material shall be free of stones larger than two inches in any dimension or as recommended by the pipe manufacturer, whichever is smaller.

2.1.7 Plastic Marking Tape: Plastic marking tape shall be acid and alkali-resistant polyethylene film, 6-inches wide with minimum thickness of 0.004 inch. Tape shall have a minimum strength of 1750 psi lengthwise and 1500 psi crosswise. The tape shall be manufactured with integral wires, foil backing or other means to enable detection by a metal detector when the tape is buried up to 3 feet deep. The tape shall be of a type specifically manufactured for marking and locating underground utilities. The metallic core of the tape shall be encased in a protective jacket or provided with other means to protect it from corrosion. Tape color shall be as specified in Table 1 and shall bear a continuous printed inscription describing the specific utility.

TABLE 1

Tape Color

Red:

Electric

Yellow:

Gas, Oil, Dangerous Materials

Orange:

Telephone, Telegraph, Television, Police, and Fire Communications

Blue:

Water Systems

Green:

Sewer Systems

PART 3 – EXECUTION:

3.1 EXCAVATION:

Excavation shall be performed to the lines and grades as indicated. During excavation, material satisfactory for backfilling shall be stockpiled in an orderly manner at a distance from the banks of the trench equal to 1/2 the depth of the excavation, but in no instance closer than 2 feet. Excavated material not required or not satisfactory for backfill shall be disposed of in accordance with all Federal, State, County, and local laws and regulations. Grading shall be done as may be necessary to prevent surface water from flowing into the excavation, and any water accumulating therein shall be removed to maintain the stability of the bottom and sides of the excavation. Unauthorized or over excavation shall be backfilled in accordance with paragraph 3.2 - "Backfilling and Compaction" at no additional cost to the Government.

3.1.1 Trench Excavation: The trench shall be excavated as recommended by the manufacturer of the pipe to be installed and in accordance with all applicable OSHA guidance. Trench walls below the top of the pipe shall be sloped, or made vertical, and of such width as recommended in the manufacturer's installation manual. Where no manufacturer's installation manual is available, trench walls shall be made vertical. Trench walls more than four feet high shall be shored, cut back to a stable slope, or provided with equivalent means of protection for employees who may be exposed to moving ground or cave in. Vertical trench walls more than three feet high shall be shored. Trench walls which are cut back shall be excavated to at least the angle of repose of the soil. Special attention shall be given to slopes which may be adversely affected by weather or moisture content. The trench width below the top of pipe shall not exceed 24 inches plus pipe outside diameter (O.D.) for pipes of less than 24 inches inside diameter and shall not exceed 36 inches plus pipe outside diameter for sizes larger than 24 inches inside diameter. Where recommended trench widths are exceeded, redesign or special installation procedures shall be utilized by the Contractor. The cost of redesign or special installation procedures shall be borne by the Contractor.

3.1.1.1 Bottom Preparation: The bottoms of trenches shall be accurately graded to provide uniform bearing and support for the bottom quadrant of each section of the pipe. Bell holes shall be excavated to the necessary size at each joint or coupling to eliminate point bearing. Stones of four inches or greater in any dimension, or as recommended by the pipe manufacturer, whichever is smaller, shall be removed to avoid point bearing.

3.1.1.2 Removal of Unyielding Material: Where unyielding material is encountered in the bottom of the trench, such material shall be removed six inches below the required grade and replaced with suitable materials as provided in paragraph 3.2 - "Backfilling and Compaction."

3.1.1.3 Removal of Unstable Material: Where unstable material is encountered in the bottom of the trench, such material shall be removed to the depth directed and replaced to the proper grade with select granular material as provided in paragraph 3.2 - "Backfilling and Compaction." When removal of unstable material is required due to the fault or neglect of the Contractor in his performance of the work, the resulting material shall be excavated and replaced by the Contractor.

3.1.1.4 Excavation for Appurtenances: Excavation for inlets and similar structures shall be sufficient to leave at least 12 inches clear between the outer structure surfaces and the face of the excavation or support members. Rock shall be cleaned of loose debris and cut to a firm surface either level, stepped, or serrated, as shown or as directed. Loose disintegrated rock and thin strata shall be removed. Removal of unstable material shall be as specified above. When concrete or masonry is to be material shall be as specified above. When concrete or masonry is to be placed in an excavated area, special care shall be taken not to disturb the bottom of the excavation. Excavation to the final grade level shall not be made until just before the concrete or masonry is to be placed.

3.1.1.5 Stockpiles: Stockpiles of satisfactory, unsatisfactory and wasted materials shall be placed and graded as specified. Stockpiles shall be kept in a neat and well drained condition, giving due consideration to drainage at all times. The ground surface at stockpile locations shall be cleared, grubbed, and sealed by rubber-tired equipment, excavated satisfactory and unsatisfactory materials shall be separately stockpiled. Stockpiles of satisfactory materials shall be protected from contamination which may destroy the quality and fitness of the stockpiled material. If the Contractor fails to protect the stockpiles, and any material becomes satisfactory material from approved sources at no additional cost to the Government. Locations of stockpiles of satisfactory materials shall be subject to prior approval of the Contracting Officer or designated representative.

3.2 BACKFILLING AND COMPACTION:

Backfill material shall consist of satisfactory material or initial backfill material as required. Backfill shall be placed in layers not exceeding 6 inches loose thickness for compaction by hand operated machine compactors, and 8 inches loose thickness for other than hand operated machines, unless otherwise specified. Each layer shall be compacted to at least 95 percent maximum density for cohesionless soils and 90 percent minimum density for cohesive soils, unless otherwise specified.

3.2.1 Trench Backfill: Trenches shall be backfilled as described in the Task Order..

3.2.1.1 Replacement of Unyielding Material: Unyielding material removed from the bottom of the trench shall be replaced with select borrow material or initial backfill material.

3.2.1.2 Replacement of Unstable Material: Unstable material removed from the bottom of the trench or excavation shall be replaced with select granular material placed in layers not exceeding 6 inches loose thickness.

3.2.1.3 Initial Backfill: Initial backfill material shall be placed and compacted with approved tampers to a height of at least one foot above the utility pipe or conduit. The backfill shall be brought up evenly on both sides of the pipe for the full length of the pipe. Care shall be taken to ensure thorough compaction of the fill under the haunches of the pipe.

3.2.1.4 Final Backfill: The remainder of the trench, except for special materials for roadways, shall be filled with satisfactory material. Backfill material shall be placed and compacted as follows:

3.2.1.4.1 Roadways: Backfill shall be placed up to the elevation at which the requirements in Specification SECTION 02225 – Earthwork. Water flooding or jetting methods of compaction will not be permitted.

3.2.1.4.2 Sidewalk, Turfed or Seeded Areas and Miscellaneous Areas: Backfill shall be deposited in layers of a maximum of 12-inch loose thickness, and compacted to 80 percent maximum density for cohesive soils and 85 percent maximum density for cohesionless soils. Compaction by water flooding or jetting shall not be permitted. This requirement shall also apply to all other areas not specifically designated above.

3.2.2 Backfill for Appurtenances: After the pre-cast inlet or similar structure has been constructed, backfill shall be placed in such a manner that the structure will not be damaged by the shock of falling earth. The backfill material shall be deposited and compacted as specified for final backfill, and shall be brought up evenly on all sides of the structure to prevent eccentric loading and excessive stress.

3.3 SPECIAL REQUIREMENTS:

Special requirements for both excavation and backfill relating to the specific utilities are as follows:

3.3.1 Plastic Marking Tape: Warning tapes shall be installed directly above the pipe, at a depth of 18 inches below finished grade unless otherwise shown.

3.4 TESTING:

Testing shall be the responsibility of the Contractor and shall be performed at no additional cost to the Government.

3.4.1 Testing Facilities: Tests shall be performed by an approved commercial testing laboratory. No work requiring testing will be permitted until the facilities have been inspected and approved by the Contracting Officer. All costs incurred for any inspection required shall be charged to the Contractor.

3.4.2 Testing of Backfill Materials: Characteristics of backfill materials shall be determined in accordance with particle size analysis of soils ASTM D422, and moisture-density relations of soils ASTM D1557. A minimum of one particle size analysis and one moisture-density relation test shall be performed on each different type of material used for bedding and backfill.

3.4.3 Field Density Tests: Tests shall be performed in sufficient numbers to ensure that the specified density is being obtained. A minimum of one field density test per lift of backfill for every 100 linear feet/(or a minimum of one per Task Order) of installation shall be performed. One moisture density relationship shall be determined for every 500 cubic yards of material used/(or a minimum of one per Task Order). Field in-place density shall be determined in accordance with ASTM D2922. When ASTM D2922 is used, the calibration curves shall be checked and adjusted using the sand cone method as described in ASTM D-1556. ASTM D2922 results in a wet unit weight of soil and when using either of these methods, ASTM D3017 shall be used to determine the moisture content of the soil. The calibration curves furnished with the moisture gauges shall be checked along with density calibration checks as described in ASTM D3017. The calibration checks of both the density and moisture gauges shall be made at the beginning of a job, on each different type of material encountered, at intervals as directed by the Contracting Officer. Copies of calibration curves, results of calibration tests, and field and laboratory density tests shall be furnished to the Contracting Officer within 24 hours of conclusion of the tests. Trenches improperly compacted shall be reopened to the depth directed, then refilled and compacted to the density specified at no additional cost to the Government. In-place density from ASTM D-2922 shall be checked by ASTM D 1556 one test per lift for every 300 LF or one test per every other lift if less than 300 LF.

3.4.4 Displacement of Sewers: After other required tests have been performed and the trench backfill compacted to the finished grade surface, the pipe shall be inspected to determine whether significant displacement has occurred. This inspection shall be conducted in the presence of the Contracting Officer or designated representative. Pipe sizes larger than 36 inches shall be entered and examined, while smaller diameter pipe shall be inspected by shining a light or laser between manholes or manhole locations, or by the use of television cameras passed through the pipe. If, in the judgment of the Contracting Officer or designated representative, the interior of the pipe shows poor alignment or any other defects that would cause improper functioning of the system, the defects shall be remedied as directed at no additional cost to the Government.

END OF SECTION

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