Installation Guide
Trench Construction
• Trench or ditch should be just wide enough to place and compact backll
around the entire pipe. Increasing the trench width increases the soil load
on the pipe. Where trench walls are stable or supported, provide a width
sucient, but no greater than necessary, to ensure working room to
properly and safely place and compact embedment materials. The space
between the pipe and trench wall must be enough for the compaction
equipment used in the pipe zone. Minimum width shall be not less than
the greater of either the pipe outside diameter plus 16” (400 mm) or the
pipe outside diameter times 1.25, plus 12” (300 mm).
• For parallel pipe installations allow 12” (300mm) between the pipes.
• As with any pipe, groundwater or seasonal high water tables may impede
installation. De-watering is necessary for a safe, and effective installation.
• Trench or ditch bottoms containing bedrock, soft muck or refuse, or other
material unable to provide long-term pipe support are unacceptable.
Unsatisfactory backll shall be removed as specied by the design engineer.
• Unless otherwise specied or instructed by a soils specialist, rock or
unyielding material shall be removed to 1’ (0.3 m) below grade and 6” (150mm)
on either side of pipe and replaced with a suitable material as directed by the
design engineer.
• For a at bottom trench, bedding must be used for support as in Figure 1. Bedding shall be loosely
placed directly under the pipe while the remainder shall be compacted in accordance with Table
1. Shaped trench bottoms may be used in accordance with ASTM F 449, see Figure 2.
• If soft area remains after excavation or if native soil can migrate into backll, use an approved synthetic
fabric (geotextile) to separate native soil from backll as recommended by the design engineer.
Backll Envelope Construction
• Place and compact backll in layers to the meet the requirements of Table 1.
• Pipes laid in parallel installations require the same backll support.
• Place and compact initial backll in layers around pipe and at least
6” (150mm) above the crown as shown in Figure 1.
• Avoid impacting pipe with compaction equipment. Inspect if there is a question regarding damage.
• The nal minimum cover shall be 1’ (0.3 m) for 3”-24” (75-600mm) pipe, measured from the
crown of the pipe to nal grade. For paved surface applications, exible (asphalt) pavement
thickness should not be included in the minimum cover as shown in Figure 1.
• If sucient cover is not provided, mound and compact material over pipe to provide
minimum cover needed for load during construction. Note: Construction trac is heavier
than typical roadway vehicles and will require a greater amount of minimum cover.