The contractor shall do all the excavation required for the
construction of the project, including clearing of the site for the
work, and the removal and disposal of all materials necessary for
construction.
A. Excavated materials may be temporarily stored along the trench, unless
otherwise noted, in a manner that will not cause damage to trees,
shrubs, fences or other property, nor that will endanger the bank
stability of the trench by imposing too great a load thereon.
B. Excavations shall be adequately braced and/or sheeted to prevent
caving or squeezing of the soil, or disturbing existing utilities
or pavement, and shall be completely dewatered prior to construction
of the sewer.
C. The subgrade shall be accurately prepared to line and grade so that
the pipe, when laid, shall have uniform bearing upon the approved
backfill, throughout its length.
D. The trench shall be backfilled closely behind the pipelaying. Unless
otherwise directed or permitted by the Director, the backfilling shall
follow at least two lengths behind pipelaying and shall be completed
to the top of the trench not more than 10 lengths behind pipelaying.
E. Pavement cutting, maintenance and reinstatement shall be done in
a manner satisfactory to the WCDPS and the Director.
F. Excavations which are to be left open overnight shall be completely
enclosed with suitable fencing and have adequately lighted barricades,
unless approved otherwise by the Director.
Pipe bedding defined. "Pipe bedding" is defined as that material
placed from a minimum of four inches below the pipe to the spring
line of the pipe. It shall consist of stone or sand, and noted on
the bedding detail. The bedding shall be removed under the bell so
that the pipe barrel will be uniformly supported for its full length.
A. The bedding material shall be placed and compacted uniformly on both
sides of the pipe to prevent lateral movement. Mechanical methods
of tamping shall be used when it is possible to do so without damaging
the pipe. Bedding shall be placed in layers of six inches or less,
as necessary to obtain thorough compaction around the pipe.
B. In the event density testing becomes necessary to resolve a question
of the sufficiency of compaction of bedding material, the minimum
acceptable density shall be 95% of maximum density, as determined
by the AASHTO T180 method.
C. Sand shall conform to granular material Class II, as defined in MDOT
8.02.05.
D. Unless otherwise authorized by the Director, all excavations shall
be backfilled at least to a point one foot above the pipe immediately
after installation.
Concrete cradle shall be constructed using MDOT Grade P1 concrete.
The cradle shall extend up on the sides of the pipe to a horizontal
plane located a minimum of 1/4 the outside diameter of the pipe above
the bottom of the pipe. The pipe shall be anchored to prevent floating
during the concrete pour.
Unstable or unsuitable material shall be removed. The embankment
shall be of suitable material with one vertical on two horizontal
fill slopes and shall be placed in one-foot layers to the proposed
top of pipe, and compacted top 95% of maximum density as determined
by the AASHTO T180 method. The embankment shall be 12 feet wide plus
four times the diameter of the pipe.
Rocks, boulders, and stones over two inches in diameter shall
be removed to provide a clearance of at least six inches from any
part of the pipe or appurtenances.
When trees are to be saved, the following rules apply:
A. Trees two inches in diameter or less may be removed, temporarily
planted, and then replanted to the final location.
B. Trenches shall be no closer than:
(1) Four feet from all trees eight inches in diameter and smaller.
(2) One-half foot per inch of the diameter of the tree. (Example: A fourteen-inch-diameter
tree will require a seven-foot distance between the edge of the trench
and the trunk of the tree.