This work shall consist of the removal and satisfactory
disposal of all material necessary for the proper construction of
pipe culverts, end walls, catch basins, drop inlets, manholes, underdrains,
sewers and service pipes.
Except where rock is encountered, care shall be taken
not to excavate below the depths required. The contractor shall furnish
and employ such shores, braces, sheeting, pumps, etc., as may be necessary
for the protection of property, proper completion of the work and
the safety of the public and employees of the contractor and the Town.
All bracing, sheeting, etc., shall be removed when no longer required
for the construction or safety of the work.
During excavation, granular material suitable for
backfilling shall be piled in an orderly manner a sufficient distance
from the banks of the trench to avoid overloading and to prevent slides
or cave-ins. All excavated materials not required or suitable for
backfill shall be removed and disposed of.
Trenches shall be of the necessary width and depth
for proper laying of pipe with a minimum clearance of eight inches
from the exterior face and in accordance with the Standard Details.
To ensure proper conditions at all times during construction,
the contractor shall provide and maintain ample means and devices
with which to intercept and/or remove promptly and dispose properly
of all water entering trenches and other excavations. Excavations
shall be kept dry until the structures, pipes and appurtenances to
be built therein have been completed to such extent that they will
not be floated or otherwise damaged.
Where rock is encountered in the excavation, it shall
be removed as required to permit the construction. Where explosives
and blasting are used, all laws and ordinances of municipal, state
and federal agencies relating to the use of explosives shall be complied
with. All blasting shall be performed by qualified personnel and proper
precautions shall be taken to protect persons, property and the work
from damage or injury from blast or explosion.
Rock shall be excavated, within the limits of the
trench, to a depth required for crushed stone or screened gravel bedding.
No rock shall project beyond the sides of the trench closer to the
outside of the pipe than six inches.
Whenever wet or otherwise unstable soil that is incapable
of properly supporting the pipe or structure is encountered as determined
by the Town Engineer, such soil shall be removed to the depth required
and refilled with gravel fill and compacted.
Gravel fill shall be used for the purpose of replacing
unsuitable material used in backfill of trenches and underneath the
pipe. Material for gravel fill shall conform to State Form 810, Article
M.02.01, Gravel Fill.
The backfill material above the center line of the
pipe and below the center line of the pipe shall be placed and compacted
by hand in six-inch layers until the backfill material is at least
12 inches compacted thickness above the top of the pipe. The backfill
material shall be suitable material from the excavation or shall be
suitable borrow material from other excavations or approved gravel
fill as herein specified. Mechanical rammers or pneumatic tampers
shall be used only after backfill has been compacted by hand to a
depth of 12 inches above the pipe. Backfill shall be compacted in
layers of not more than six inches' compacted thickness. No stones
other than bedding stone shall be placed within 18 inches of the pipe
in backfillings. When any stone is used in the remainder of backfilling,
each piece shall be embedded in dirt, and no stone weighing over 20
pounds shall be included in the trench. Nesting of stones will not
be allowed. The intent of this specification is to require thorough
tamping of bedding and backfill material.
The bottom of the trenches shall be accurately graded
to provide bedding which consists of a uniform bearing and support
for each section of the pipe on undisturbed soil at every point along
its entire length, except for the portions of the pipe sections where
it is necessary to excavate for bell holes and for the proper seating
of pipe joints. Bell holes and depressions for joints shall be dug
after the trench bottom has been graded, and in order that the pipe
rests on the prepared bottom for as nearly its full length as practicable,
bell holes and depressions shall be only of such length, depth and
width as required for properly making the particular type of joint.