Home Improvement Siding Kitchen Windows Vinyl Pools Patio Security 0183

Section 19 – Trench Excavation, Bedding and Backfill

Ductile Iron water distribution mains shall have six inches (6”) of sand bedding material that

conforms to the requirements of Section 50-13.02, “Graded Sand”, of these Specifications. If

existing soil is too porous to hold sand, a geotextile fabric placed on the trench bottom and

covered with six inches (6”) of sand may be used. The use and type of geotextile must be

approved by the Agency. The Ductile Iron distribution main, fittings, and cast iron fittings shall

be encased in eight– (8) mil polyethylene encasement in accordance with AWWA C105.

19-2.02 Initial Backfill

Initial backfill shall be furnished and placed as shown or specified in the Contract, and in

accordance with the requirements in these Specifications.

Unless otherwise specified in the Special Provisions, initial backfill for gravity sewer

construction shall be as detailed on Standard Drawing 7-4. Initial backfill shall be the material

between the top of the bedding material and twelve inches (12”) above the top of the pipe.

19-2.02.B Storm Drain

Unless otherwise specified in the Special Provisions, the following initial backfill

requirements shall apply. For cast-in-place concrete pipe, initial backfill shall conform to

Section 36-14, “Cast-in-Place Concrete Pipe (CIPCP) – Backfill”, of these Specifications and

Standard Drawing 9-1. For all other pipes initial backfill for storm drain construction shall

conform to this Section 19 and Standard Drawing 9-1.

Granular materials shall conform to Section 50-14, "Crushed Rock”, of these Specifications.

For field conditions requiring control density backfill the material shall conform to Section 50-15,

"Control Density Backfill", of these Specifications. For field conditions requiring portland cement

concrete backfill the material shall conform to Section 50-5.01, "Portland Cement Concrete -

Composition”, Class "C”, of these Specifications.

After placement of bedding, the Contractor shall place initial backfill material to the spring

line of the pipe, thoroughly compacting it by shovel slicing or light tamping to provide proper

support under the pipe haunches. The remaining initial backfill material shall be placed per

Standard Drawing 9-1. Care shall be used not to disturb or displace the pipe. When using

control density or concrete backfill, the Contractor shall anchor the pipe to prevent floating or

displacement of the pipe. The anchors shall be spaced to insure a continuous even grade in

the flow line of the pipe.

19-2.02.C Water Distribution Systems

Initial backfill for water distribution systems shall conform to the requirements of Standard

Drawing 8-17. Unless otherwise specified in the Special Provisions, initial backfill for water

distribution systems, including water mains, fire hydrant branch leads, and water services, shall

be sand conforming to the requirements in Section 50-13.02, “Graded Sand”, of these

Specifications. Ductile iron distribution mains shall have sand backfill to eight inches (8”) above

the top of the distribution main. Initial backfill for PVC water distribution pipe may be of native

material or sand. Initial backfill for ductile iron or cast iron fittings used with PVC pipe shall be

sand to eight inches (8”) above the top of the fittings.

Initial backfill shall be placed immediately after pipe joints have been completed and

inspected by the Agency. The material shall be carefully placed so as not to disturb or damage

the pipe, and shall be brought up evenly on both sides. Initial backfill material shall be placed in

layers not exceeding eight inches (8”) in depth before compaction at or near optimum moisture

content. Compaction shall be by mechanical pneumatic or vibratory compaction equipment

approved by the Agency. Ponding and jetting methods will not be permitted, although water

may be sprayed from a two-inch (2”) truck hose onto initial and final sand backfill. The

compacted material must achieve a relative compaction of at least ninety percent (90%) as

determined by ASTM Designation: D 698. If steel piling is used, it may be removed