an=2>
TRENCH EXCAVATION AND BACKFILL A. City of North Augusta

Trench Excavation and Backfill
TRENCH EXCAVATION AND BACKFILL
A.
SCOPE: Furnish all material, equipment, and labor required to excavate
and backfill the trench for the installation of water, sanitary sewer, and
storm drainage pipelines as specified, as shown on the Plans, and as
directed by the Engineer.
B.
EXISTING IMPROVEMENTS: Streets, sidewalks, driveways, power/
cable/telephone lines, gas lines, water lines, sewers, storm drains and
other existing improvements shall be maintained and protected from
damage. Any aerial, surface or subsurface improvements damaged
during the course of the work shall be repaired to the satisfaction of the
Engineer. Satisfactory provisions shall be made for the maintenance of
traffic on streets, driveways, and walkways.

Prior to any excavation, the Contractor shall notify all utilities and utility
locating services to provide locations for buried utilities. The contractor
shall obtain all necessary permits (grading, building, water, sewer,
encroachment, etc.) prior to beginning work.
C.
TREE PROTECTION: Care shall be exercised to protect trees to be left
standing. Within the branch spread of such trees, all trenching shall be
performed with extra care. The trench shall be opened when the work can
be installed immediately. Injured roots shall be pruned cleanly and backfill
placed as soon as possible.
D.
EXCAVATION: Trench excavations shall be made by the open cut
method to the depths indicated on the drawings or as otherwise specified.
All excavated materials not suitable for backfill shall be wasted on site or
removed from the site as directed.
The excavated trench shall be at least 12 inches wider but not more than
16 inches wider than the outside diameter of the pipe being installed. The
trench shall be excavated true to line to provide 6 inches to 8 inches
clearance on each side of the pipe. The bottom of the trench shall be
accurately graded to provide uniform bearing and support along the pipe
barrel. Bell holes shall be excavated to allow sufficient space to make the
joint and to insure that the pipe will rest evenly on the bottom of the trench.
Bell hole dimensions shall be as recommended by the pipe manufacturer.
Excavations for structures and other accessories shall be sufficient to
provide at least 12 inches clearance between the structure and the trench
wall.

If rock is encountered, the trench shall be excavated to a minimum depth City of North Augusta

Trench Excavation and Backfill
6 inches below the pipe. The trench shall then be backfilled with select
material, compacted in place, to the depth required for pipe installation.
Wet or other unsuitable material encountered in the trench bottom shall be
removed to a depth required to gain sufficient bearing strength as directed
by the Engineer. The trench shall then be backfilled with select material,
compacted in place, to the depth required for pipe installation. If rock or
other unsuitable material is encountered in the excavation for structures,
the excavated area below the structure shall be backfilled with stone or
concrete as directed by the Engineer
E.
STOCKPILING EXCAVATED MATERIAL: Material excavated from the
trench that is suitable for backfill shall be stockpiled a safe distance away
from the excavation to allow room for adequate angle of repose and to
protect the excavation. No material may be placed within three feet of the
nearest edge of the trench. Material unsuitable for backfilling, as
determined by the Engineer, shall be wasted on site or removed from the
site and disposed of by the Contractor, as approved by the Engineer.
F.
SHORING AND SHEETING: All shoring, sheeting, and bracing required
to perform and protect the excavation and to safeguard employees and
the public shall be performed. Whenever sheeting is driven to depth
below the elevation of the top of the pipe, that portion of the sheeting
below the elevation for the top of the pipe shall not be disturbed or
removed. Sheeting left in place shall be cut off not less than 1 foot below
finished grade. No sheeting shall be removed until the excavation is
substantially backfilled as hereinafter specified.
G.
WATER REMOVAL: The Contractor shall be required to control
groundwater and prevent the accumulation of water within excavations.
Well pointing, pumping, or other methods shall be as approved by the
Engineer. The Contractor shall also control surface water runoff to
prevent the accumulation of water in excavated trenches. Water shall not
be allowed to rise in open excavations after pipe or structures have been
placed. No work shall be performed within the trench until the Contractor
demonstrates that groundwater and surface water runoff is controlled. If
water accumulates within an excavation, the Contractor will be required to
remove the water and saturated materials and backfill with approved
material. Water removed from excavations shall be discharged at points
where it will not damage adjacent property or facilities.
H.
BLASTING: Explosives are to be used only within legal limitations.
Before explosives are used, all necessary permits for this work shall be
secured and all precautions taken in the blasting operations to prevent
damage to property, persons, or facilities. The Contractor shall assume
full liability for any damage that may occur during the use of explosives.
No blast shall be set off within fifty (50) feet of existing pipe or pipe already City of North Augusta

Trench Excavation and Backfill
installed in the trench.
I.
BACKFILLING: Trenches and other excavations shall not be backfilled
until all required tests are performed and the work has bee approved by
the Engineer. The trenches shall then be carefully backfilled with
approved excavated materials or other material approved by the Engineer.
Backfill shall not contain organic material, blasted rock, broken concrete or
pavement, construction debris, frozen earth, etc.

For backfill up to a level 1 foot over the top of pressure pipelines and 2
feet above the top of gravity pipelines, only selected materials shall be
used. Select materials shall be finely divided material free from debris,
organic material and rock, and may be suitable job excavated material or
shall be provided by the Contractor from other sources. The backfill shall
be placed in uniform layers not exceeding 6 inches in depth. Each layer
shall be moistened and carefully and uniformly tamped with mechanical
tampers or other suitable tools to 95% standard proctor compaction. Each
layer shall be placed and tamped under the pipe haunches with care and
thoroughness so as to eliminate the possibility of voids or lateral
displacement.

The remainder of the backfill material shall then be placed and compacted
above the level specified above. In areas not subject to traffic, the backfill
shall be placed in 12-inch layers, and each layer moistened and
compacted to a density approximating that of the surrounding earth.
Under roadways, driveways, paved areas, parking lots, along roadway
shoulders and other areas subject to traffic, the backfill shall be placed in
6-inch layers and each layer moistened and compacted to 95% standard
proctor compaction. Any trenches which are improperly backfilled, or
where settlement occurs, shall be reopened to the depth required for
proper compaction, then refilled and compacted with the surface restored
to the required grade and compaction. Along all portions of the trenches
not located in roadways, the ground shall be graded to a reasonable
uniformity and the mounding over the trenches left in a neat condition
satisfactory to the Engineer. All compaction shall be verified by nuclear
density gauge on a random basis as specified by the Engineer in the field.
Compaction tests shall be paid for by the contractor.

Sheeting not specified to be left in place shall be removed as the
backfilling progresses. Sheeting shall be removed in such a manner as to
avoid caving the trench. Voids left by the removal of sheeting and shoring
shall be carefully filled and compacted. Where, in the opinion of the
Engineer, damage is liable to result from withdrawing sheeting, the
sheeting will be ordered to be left in place. City of North Augusta

Trench Excavation and Backfill
J.
PAVEMENT REPLACEMENT: The Contractor shall replace or repair all
road/street/highway pavement and sidewalks that are damaged by this
construction as specified herein and/or as required by the SCDOT
Highway Encroachment .
Pavement repairs shall be made by saw-cutting the existing pavement
outside the damaged area to provide eight inches of bearing on
undisturbed soil on each side of the excavation. The existing asphalt
and/or concrete and/or base materials shall be removed to the depth
required to place the patch. The following requirements are minimum
thickness and in all cases the patch shall not be less than the existing
pavement thickness.
1.
Concrete Street Pavement: Replace with 8 inches thick concrete
(3000 psi).
2.
Asphalt Pavement: Replace with 2" asphalt concrete (Type III)
surface over:
a. 8" thick concrete (3000 psi).
b. Controlled Density Fill ("Flowable Fill") poured the entire depth
of the trench. OR
c. Compacted fill subgrade 95% Modified Pro