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Section 19 – Trench Excavation, Bedding and Backfill

simultaneously with placement and compaction of intermediate backfill. Trench jacks or other

shoring shall not be removed before completion of initial backfill.

19-2.03 Trench Backfill

Trench backfill shall consist of material placed between the initial backfill and subgrade in

paved areas or to the top of the trench in unpaved areas, unless otherwise shown or specified

The trench backfill material may be native material excavated at the work site if the trench

depth is greater than four feet (4’) measured from the top pipe to the finished road surface.

Such material must be free of organic or other unsuitable materials as determined by the

Agency that may cause voids or depressions to develop during or after placement of the backfill.

Rocks, stones and solid earth chunks exceeding three inches (3”) in greatest dimension shall be

removed from the trench backfill material.

Trench backfill material shall be placed in layers not exceeding eight inches (8”) in depth

before compaction at or near optimum moisture content. Until the total backfill above the top of

the pipe exceeds three feet (3’), machine-placed backfill material shall not be allowed to

"freefall" more than two feet (2’).

The backfill material for trench depths less than four feet (4’) measured from the top pipe to

the finished road surface shall be imported granular material, uniformly graded Class 2

aggregate base conforming to the requirements in Section 50-7, “Aggregate Bases”, of these

Specifications. The imported granular material shall be placed in lifts not to exceed six inches

(6”) after compaction. Compaction requirements for imported granular material shall be the

same as required for compaction of job excavated native material.

Unless otherwise shown or specified in the Contract, compaction of all backfill material shall

be by mechanical pneumatic or vibratory compaction equipment. Ponding and jetting methods

will not be permitted, except by written permission of the Agency.

Unless otherwise shown or specified in the Contract, trench backfill material shall be

compacted to a relative compaction of not less than ninety percent (90%), as determined by

ASTM Designation: D 1557. The top six inches (6”) below the subgrade shall be compacted to

a relative compaction of ninety-five percent (95%), except that trenches in easements outside

the street rights-of-way may be compacted to ninety percent (90%) relative compaction

throughout the depth. Compaction testing will be performed by the Owner and the cost thereof

will be borne by the Agency, except that retests of areas which fail to meet the required

compaction will be charged to the Contractor and deducted from any payment due the

Unless otherwise specified in the Special Provisions, the Contractor has the option to use

imported granular material for trench backfill in place of native material excavated at the work

site. The imported granular material shall be uniformly graded Class 2 aggregate base

conforming to the requirements in Section 50-7, “Aggregate Bases”, of these Specifications.

The imported granular material shall be placed in lifts not to exceed six inches (6”) after

compaction. Compaction requirements for imported granular material shall be the same as

required for compaction of job excavated native material. Unless otherwise specified in the

Special Provisions, the optional use of imported granular material for trench backfill will be at

the Contractor’s expense.

Full compensation for furnishing, placing, and compacting pipe bedding and trench backfill

materials is included in the prices paid per linear foot of the respective sizes, grades, and types

of pipes listed in the Contract, and no additional compensation will be paid.