02223.doc

SECTION 02223

BACKFILLING FOR UTILITIES SYSTEMS

PART 1

GENERAL

1.1 The publications listed below form a part of this specification to the extent referenced. The publications are referred to in the test by the basic designation only.

A. Military Standards (Mil. Std.)

1. MIL-STD-619B: Unified Soil Classification System for Roads, Airfields, Embankments and Foundations

2. MIL-STD-621A: Test Method for Pavement Subgrade, Subbase, Notices 1 and 2 and Base-Course Materials

B. American Society of Testing and Materials (ASTM) Publications

C.

E 548-79: Generic Criteria for Use in the Evaluation of Testing and Inspection Agencies

PART 2

PRODUCTS

2.1 Satisfactory Materials:

Satisfactory materials shall consist of any material classified by MIL-STD-619 as GW, GP, and SW.

2.2 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 2 inches, and materials classified in MIL-STD-619, as PT, OH, and OL. Unsatisfactory materials also include man-made fills, refuse, or backfills from previous construction.

2.3 Cohesionless and Cohesive Materials:

Cohesionless materials shall include materials classified in MIL-STD-619 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.

2.4 Rock:

Rock shall consist of boulders measuring 1/2 cubic yard or more and materials that cannot be removed without systematic drilling and blasting such as rock material in ledges, bedded deposits, unstratified masses and conglomerate deposits, and below ground concrete or masonry structures, exceeding 1/2 cubic yard in volume, except that pavements will not be considered as rock.

2.5 Unyielding Material:

Unyielding material shall consist of rock and gravelly soils with stones greater than 3 inches in any dimension or as defined by the pipe manufacturer, whichever is smaller.

2.6 Unstable Material:

Unstable material shall consist of materials too wet to properly support the utility pipe, conduit, or appurtenance structure.

2.7 Select Granular Material:

Select granular material shall consist of well-graded sand, gravel, crushed gravel, crushed stone or crushed slag composed of hard, tough and durable particles, and shall contain not more than 10 percent by weight of material passing a No. 200 mesh sieve and no less than 95 percent by weight passing the 1-inch sieve. The maximum allowable aggregate size shall be 2 inches, or the maximum size recommended by the pipe manufacturer, whichever is smaller.

2.8 Degree of Compaction:

Degree of compaction shall be expressed as a percentage of the maximum density obtained by the test procedure presented in MIL-STD-621, Method 100, compaction effort designation CE 55.

2.9 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 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 specified in Table 1 and bear a continuous printed inscription describing the specific utility. Utilities are to also have tracer wire installed.

TABLE 1 - TAPE COLOR

Yellow: Gas

Blue: Water Systems

Red: Electric

Green: Sewer

Orange: Telephone

PART 3

EXECUTION

3.1 EXCAVATION – GENERAL:

Excavation of every description and of whatever substances encountered shall be performed to the lines and grades indicated. Rock excavation shall include removal and disposition of material defined as rock in Para 2.0, Definitions. Earth excavation shall include removal and disposal of material not classified as rock excavation. During excavation, material satisfactory for backfilling shall be stockpiled in an orderly manner. Adequate drainage shall be provided for the stockpiles and surrounding areas by means of ditches, dikes, or other approved methods. The stockpiles shall also be protected from contamination with unsatisfactory excavated material or other material that may destroy the quality and fitness of the suitable stockpiled material. If the Contractor fails to protect the stockpiles and any material becomes unsatisfactory as a result, such material, if directed, shall be removed and replaced with satisfactory on-site or imported material from approved sources at no additional cost to the Government. Excavated material not required or not satisfactory for backfill shall be removed from the site. 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 so that the stability of the bottom and sides of the excavation is maintained. Unauthorized overexcavation shall be backfilled in accordance with these specifications, at no additional cost to the Government.

3.2 Trench Excavation:

The trench shall be excavated as recommended by the manufacturer of the pipe to be installed. Trench walls below and above the top of the pipe shall be sloped, or made vertical, as recommended in the manufacturer's installation manual. The trench width below the top of the pipe shall not exceed that recommended in the installation manual. Where no manufacturer's installation manuals are available, trench walls below the top of the pipe shall be vertical, and trench walls above the top of the pipe shall be sloped as required to properly complete the work. Trench width below the top of the pipe shall not exceed 24 inches plus pipe outside diameter (OD).

1. Bottom Preparation: The Contractor shall excavate for and provide an initial granular bedding at least 4 inches thick. This bedding material shall be placed at a uniform density with minimum compaction and shall be accurately graded to provide uniform bearing and support for the bottom quadrant of each section of the pipe. Stones of 2 inches or greater in any dimension, or as recommended by the pipe manufactured, whichever is smaller, shall be removed to avoid point bearing.

2. Removal of Unyielding Material: Where overdepth is not indicated and unyielding material is encountered in the bottom of the trench, such material shall be removed 4 inches below the required grade and replaced with suitable materials as provided in herein.

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 materials as provided herein. 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 without additional cost to the Government.

3.3 Excavation for Appurtenances:

Excavation for manholes, catch-basins, inlets, or similar structures shall be of sufficient size to permit the placement and removal of forms for the full length and width of structure footings and foundations as shown. Removal of unstable material shall be 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.

3.4

BACKFILLING – GENERAL:

Backfill material shall consist of satisfactory material. 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, unless otherwise specified herein.

3.5 Trench Backfill:

A. Trenches shall be backfilled to grade. The trench shall not be backfilled until all specified tests are performed.

1. Replacement of Unyielding Material: Unyielding material removed from the bottom of the trench shall be replaced with satisfactory material.

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. Bedding and Initial Backfill: Bedding shall be of the type and thickness recommended by the pipe manufacturer. Maximum stone size shall not exceed 2 inches, or the maximum size recommended by the pipe manufacturer, whichever is smaller. Initial backfill material shall be placed in layers of a maximum of 6 inches loose thickness and compacted with approved tampers to the density of the adjacent soil, and 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 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. Backfill material in this portion of the trench shall consist of satisfactory material at a moisture content that will facilitate compaction, free from stones of such size as recommended by the pipe manufacturer, or larger than 2 inches in any dimension, whichever is smaller, except that where the pipe is coated or wrapped for protection against corrosion, the backfill material shall be free of stones larger than 1 inch in any dimension, or as recommended by the pipe manufacturer, whichever is smaller.

4. Final Backfill: The remainder of the trench, except for special materials for roadways, railroads and airfields, shall be backfilled with satisfactory material. Backfill material shall be deposited and compacted as follows:

a. Roadways: Backfill shall be deposited in layers of a maximum of 8 inches loose thickness, and compacted to 95 percent maximum density for cohesive soils and 95 percent maximum density for cohesionless soils, up to the elevation where requirements for pavement subgrade materials and compaction shall control. Compaction by water flooding or jetting will not be permitted.

b. Sidewalks, Turfed or Seeded Areas and Miscellaneous Areas: Backfill shall be deposited in layers of a maximum of 12 inch loose thickness, and compacted to 85 percent maximum density for cohesive soils and 90 percent maximum density for cohesionless soils. Compaction by water flooding or jetting will not be permitted. This requirement shall also apply to all other areas not specifically designated above.

3.6 Backfill for Appurtenances:

After the manhole, catch basin, 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 placed in such a manner as to prevent eccentric loading and excessive stress on the structure.

3.7 Testing:

The number of density tests required will be as called for on the plans, or one test every 500 linear feet of trench with a minimum of one test per trench. Location of tests shall be determined by the Contracting Officer. The results shall be processed in accordance with Section 01400 of these specifications.

3.8

SPECIAL REQUIREMENTS

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

A. Electric, Gas and Telephone Distribution: Trenches shall be excavated to a depth that will provide not less than 24 inches of cover.

B. Sewer and Waterlines: Trenches shall be of a depth to provide a minimum cover of 36 inches for sewer and 36 inches for water from the existing ground surface, or from the indicated finished grade, whichever is lower (when possible for sewer slope), to the top of the pipe.

C. Plastic Marking Tape: Warning tapes shall be installed directly above the pipe, at a depth of 15 inches below finished grade unless otherwise shown.

END OF SECTION

02223 – 6 H:\8348\8348003.23\Docs\B-3 Specs\Division 2\02223.doc November 5, 2004