SCOPE OF WORK
The scope of work under this section covers
excavation of materials from the stockpile area, if required, hauling to the
places of fill, spreading, compacting, finishing, and incidental dewatering
where required for the general site fill, construction of the core for any
embankment, structural backfill, trench backfill and other miscellaneous fill.
The Contractor shall perform filling/backfilling
work in accordance with this Specification and as shown on the approved
drawings or as directed by the Owner.
MATERIAL SOURCES
The sources of material shall be materials
previously excavated at the Site by the Contractor or from off-Site sources.
General fill material shall be well graded, no
more than 1 5% passing No. 200 screen, maximum particle size 75 mm.
FILL/BACKFILL PLACEMENT
Compacting Equipment
Compacting equipment shall be of such design,
weight and quality as is required to obtain the densities specified herein.
Areas inaccessible to self-propelled compacting
equipment shall be compacted by hand operated mechanical tampers or vibrators.
Self-propelled compacting equipment, i.e.,
sheep's foot rollers and segmental pad rollers, and hand operated mechanical
tampers and vibrators, shall efficiently perform compaction in accordance with
this specification and as indicated.
No plea by the Contractor that the equipment he
has available at the Project Site cannot produce the densities specified will
be accepted by the Owner. The Contractor
shall furnish equipment as required.
Structural & General Site Fill
Preparation of Sub grade:
Sub grade to receive Structural Fill material
will be inspected by the Owner to determine if it is suitable and has
sufficient bearing capacity for the material and loads to be placed on it.
If sub grade is not suitable, as determined by
the Owner, the Contractor may be directed to perform additional excavation with
compensation. Thereof, made as specified in the Contract.
Compaction Densities: Material shall be brought
up to grade elevation indicated on the drawings, with suitable moisture control
and compaction throughout placement, to produce the following densities:
a. Type
structural fill material: to 90 percent of maximum dry density per ASTM D1557,
Test Method indicated.
b. Type
SFG material: to a minimum of 85 percent of relative density per ASTM D2049,
Test Method indicated.
Placing Material:
a. Unless
otherwise indicated, structural and general site fill material shall be placed
within two percent of the optimum moisture content as applicable, in uniform
layers not over 150 mm (loose measure).
b. The
Contractor shall add water or dry-out material to maintain the optimum moisture
content throughout placing and compacting.
Trench Fill Materials
Materials shall be approved fill materials from
the site excavation or the off-site sources.
Sand material shall be no more than 1 0% passing
No. 200 screen, maximum particle size No. 4.
Fill in the excavated trenches shall be placed
in layers and method of placement of the fill shall be approved by the
Owner. Prior to the start of the fill
placement, the Contractor shall submit a statement describing in greater detail
his proposed method of fill placement in the excavated trenches area for the
Owner's approval.
The fill shall be placed in layers not exceeding
a thickness of 300 mm (loose measure) and compacted to produce densities to a
minimum of 90% relative density per ASTM D2049, Test Method Indicated.
BACKFILL AROUND STRUCTURES
BACKFILLING OF PIPE TRENCHES AND CUTS
General
Backfilling around pipe shall not be performed
until pipe runs have been bedded inspected and tested.
Care shall be exercised in placing and
compacting material around pipes to maintain the material approximately at the
same level, not in excess of a 300 mm differential, on both sides of the pipe,
throughout the placing and compacting of the material.
Placing and compacting of material shall be
performed simultaneously on both sides of pipes in such a manner as will
prevent injurious side pressures on piping.
Material shall be thoroughly compacted using
hand operated power tampers until compacted material is at least 600 mm above
pipe.
Self-propelled compaction equipment shall not be
used above pipe until the compacted material has reached the 600-mm minimum,
unless approved by the Owner.
When a flat bed is required for the bottom of a
trench for pipes, granular material shall be provided for bedding to depths
indicated on the approved drawings. If unsuitable soil, as determined by the
Owner is encountered and it is directed to be removed, the Contractor shall
provide the additional depth of granular compacted bedding required. Bedding for contour cuts shall be provided as
indicated on the-approved drawing.
Bedding and Backfilling Material Placement
a. For
coated pipe, granular bedding and backfill material shall be crushed stone,
coarse sand or gravel or other material approved by the Owner. Unless otherwise directed by the Owner,
bedding and backfilling material shall conform to ASTM C33, and be not larger
than 10 mm in size.
Bedding material, material under haunches and
along sides of pipe of a point 1 50 mm above the top of the pipe shall be this
material. Care shall be taken in placing material to prevent damage to pipe
coating.
b. For
uncoated pipe, granular bedding and backfill material shall be type Structural
Fill Material. Bedding material and material under haunches and along sides of
pipe to a point 150 mm above the top of pipes shall be this material.
c. Compaction
densities for material (both ASTM C33 and Type Structural Fill Material) shall
be per Sub clause ‘Trench Fill Material’.
d. Material
from 1 50 mm above the top of pipes to indicate grade shall be selected
material approved by the Owner. This
material shall be placed and compacted per Sub clause ‘Structural & General
Site Fill’ or ‘Trench Fill Material’ as applicable for the materials to be
used.
Backfilling of Fiberglass Reinforced Pipe (FRP)
Plastic FR pipe includes RTRP (Rein forced
Thermosetting Resin Pipe) and RPMP (Reinforced Plastic Mortar Pipe) and may be
of any type or grade, lined or unlined, per ASTM D2310.
The manufacturer of the pipe shall be advised by
the Contractor of the soil conditions expected to be encountered in bedding and
backfilling pipe trenches or cuts. Promptly thereafter the pipe manufacturer
shall submit recommended procedures for cut, slope, bedding material, bedding
depth, haunch and fill over pipe utilizing either available material from the
Site, or more appropriate material obtained off-Site. These procedures will be
reviewed and shall be approved by the Owner prior to placement of the Fiberglass
Reinforced Pipe.
Bedding and haunch material (to a minimum height
above the top of pipe of c 300,mm) will be Type Structural Fill material. Material above Type SFG material shall be
randomly fill or as directed by the Owner.
Depth of each layer of material placed shall be
as directed by the pipe manufacturer, but not greater than 150 mm (loose fill
layer thickness) and shall be compacted using portable tampers.
Care shall be taken during placement to assure
evenness of compaction densities, especially under joints between pipe
sections, as well as to avoid floatation of the pipe.
BACKFILLING OF ELECTRICAL DUCT-BANKS AND DIRECT
BURIAL ABLE
Duct Banks
Material directly above and on both sides of
duct banks may be material excavated from the trench or cut, unless otherwise
indicated on the drawings, providing that the maximum size of stone in the
material is not greater than 50 mm.
Compaction shall conform to the requirements of
Sub clause ‘Structural & General Site Fill’ or ‘Trench Fill Material’, as
applicable.
Direct-Burial Cable
Material around direct-burial cable may be
material excavated from the trench or cut, providing it is free from debris or
coarse aggregate. Maximum size of stone
shall not exceed 50 mm in the fill material.
Compaction shall conform to the requirements of
Sub clause ‘Structural and General Site Fill’ or ‘Trench Fill Materials’
paragraphs above as applicable.
SURFACE FILL OF SUBSTATION
Materials
General
Fill material shall be clean, washed gravel or
crushed stone and shall be free of foreign matter. Crushed stone shall be
tough, durable, free from an excessive quantity of flat, elongated, soft or
disintegrated material.
Fire Protection Fill
Fire protection fill shall have standard size #3
gradation in accordance with ASTM D448.
General Fill
General fill shall conform to the following
gradations:
Nominal
Size % by Weight
Square
Openings Passing
38
mm 100
25
mm 90 100
13
mm 60 90
No.
4 35 55
No.
16 10 40
No.
200 0 12
Performance
Preparation of subgrade
Sod, vegetation, roots, debris and other organic
matter shall be removed from the fill areas.
Sub grade shall be graded as required and shall
be free of pockets and high spots and shall be approved by the Owner prior to
the placement of fill.
The fill area shall have special drainage
facilities.
Placing of Fill
Fire protection fill shall be placed in areas
designated on the approved drawings as "Fire Protection Fill Area".
General fill shall be placed in the areas designated on the approved drawing as
"General Fill Area".
Fire protection fill and general fill may be
placed prior to electrical installation.
Fire protection fill shall not be rolled, tamped
or packed. Finished surface shall be level and no traffic is permitted on fill
during placing operations.
General fill shall be compacted by rolling with
a 10 ton or heavier vibratory roller with a minimum of 2 passes per layer. The
maximum lift thickness shall be 15 cm. Finished surface shall be level.
The entire substation area within the fence,
excluding the building, roads, parking, trenches and foundations, shall be
covered with a minimum 200 mm thick general surface fill.