Trenches, Backfill, Anchors, and Supports

MIL-HDBK-1005/7A

e) Where a line must be maintained as an electrical

conductor for cathodic protection, use bonding cables and lugs.

7.1.5.4

Polyvinyl Chloride (PVC) Joints. PVC joints should be

selected as specified in AWWA C905, Polyvinyl Chloride (PVC)

Water Transmission Pipe and Fabricated Fittings, 14 in. Through

36 in. For Water Transmission and Distribution and AWWA C907,

Polyvinyl Chloride (PVC) Pressure Fittings for Water 4 in.

Through 8 in.

7.1.5.5

FRP-TR Joints . AWWA C950 standards should be followed

in selecting FRP-TR Joints.

7.1.5.6

Polyethylene Joints.

AWWA C906 standards should be

followed.

7.1.6

Trenches, Backfill, Anchors, and Supports. Follow

AWWA C600, Installation of Ductile-Iron Water Mains and Their

Appurtenances, or AWWA C605, Underground Installation of

Polyvinyl Chloride (PVC) Pressure Pipe, when considering

trenches, backfill anchors, and supports.

7.1.6.1

Trench Conditions . Trench bottoms in stiff material

should be cut 6 in. below pipe inverts for nominal pipe sizes 24

in. or smaller and 9 in. below pipe inverts for nominal pipe

sizes 30 in. and larger to provide proper bedding. (Refer to

AWWA C600 and AWWA C605.)

7.1.6.2

Bedding . No pipe should rest directly on rocks or

boulders. Except as provided in the following statement, all

pipes should be uniformly supported throughout their lengths on

a compacted base using firm trench soil or granular materials.

Full -length crushed stone or gravel bedding may support the pipe

where soils are soft and set. Where the ground has inadequate

bearing value, provide pipe supports and stringers. Bedding

material or a select backfill material should be installed from

the spring line of the pipe to a minimum of 6 in. over the pipe.

7.1.6.3

Supports. Exposed pipe should be supported either on

saddles or by hangers. Supports should be spaced to limit

deflection of steel pipe to a maximum of 1/360 of the span, and

to prevent over stressing any joints.

7.1.6.4

Anchorage . Anchorages should also be provided as

required to accommodate expansion due to temperature rise.

92