B. TRENCHES:
1.
Qo
Bedding as detailed and specified shall be furnished and installed beneath the
pipeline prior to placement of the pipeline. A minimum bedding thickness shall
be maintained between the pipe and undisturbed material, as shown on the
Drawings.
As soon as practicable after pipes have been laid, backfilling shall be started.
Unless otherwise indicated on the Drawings, select backfill shall be placed by
hand shovel in 6-inch thick lifts up to a minimum level of 12-inches above the
top of pipe. This area of backfill 1s considered the zone around the pipe and
shall be thoroughly compacted before the remainder of the trench 1s backfilled.
Compaction of each lift in the zone around the pipe shall be done by use of
power-driven tampers weighing at least 20 pounds or by vibratory compactors.
Care shall be taken that material close to the bank, as well as in all other
portions of the trench, is thoroughly compacted to densities required.
Trench backfill shall be placed from the top of the select backfill to the
specified material at grade (loam, pavement sub-base, etc.). Fill compaction
shall meet the density requirements of this specification.
Water Jetting:
a. Water jetting may be used when the backfill material contains less than 10
percent passing the number 200 sieve, but shall be used only if approved
by the Engineer.
b. Contractor shall submit a detailed plan describing the procedures he
intends to use for water jetting to the Engineer for approval prior to any
water jetting taking place.
c. Compaction of backfill placed by water jetting shall conform to the
requirements of this specification.
If the materials above the trench bottom are unsuitable for backfill, the
Contractor shall furnish and place backfill materials meeting the requirements
for trench backfill, as shown on the drawings or specified herein.
Should the Engineer order crushed stone for utility supports or for other
purposes, the Contractor shall furnish and install the crushed stone as directed
by the Engineer.
In roadways, the specified base course gravels and pavement shall be placed as
specified.
A tracer tape shall be furnished and installed as specified Section 02518,
TRACER TAPE
C. BACKFILLING ADJACENT TO STRUCTURES:
1. The Contractor shall not place backfill against or on structures until they have
attained sufficient strength to support the loads to which they will be subjected.
Excavated material approved by the Engineer may be used in backfilling
around structures. Backfill material shall be thoroughly compacted
2022 Sewer Replacement Project Earthwork
Nashua, NH 02300-7
