This document is the Single Wall HDPE Pipe Installation Guide. Backfill selection & envelope construction and trench construction discussed.

The recommendations presented here detail how to install a dependable subsurface drainage or groundwater control system. Installation with proper backfill materials, compaction levels, and placement procedures are essential to achieve long term system performance. These recommendations assume the drainage designer used design criteria available from ASTM F449 and ADS.

For backfill selection, only native soil meeting class I, II, or III are acceptable backfill materials. Class I materials can be dumped around pipe. Lightly tamp or knife to ensure voids are eliminated. Non-cohesive sand, sand/gravel mixes and other Class II or III materials must be compacted to remove voids. For pipe with burial depths 8’ or less, compaction may not be necessary. A table with the values for Classes of Embedment and backfill materials shown.

For trench construction, trench or ditch should be just wide enough to place and compact backfill around the entire pipe. More instruction is offered with supporting trench width and pipe diameter figures.

Backfill envelope construction lists steps when placing unit and initial backfill. A diagram is provided. Typical Backfill Structure figure is provided.

For Alternate Backfill Methods – Shaped Trench Bottoms, shaped trench bottoms may be used in lieu of the standard trench, provided a free flowing pea gravel or small rock chips are used to fill in the resultant void areas. Pea gravel or small chips shall be clean material passing a 3/8 inch (9.5mm) sieve meeting the class I, II, or III requirements of ASTM D 2321. This applies only to those insitu soil conditions where the native soil can be cut to a stable shaped trench. Line and grade may be affected due to the use of a modified trench bottom which may affect the pipe hydraulics. Shaped Trench Bottoms figures show “V” Groove, Trapezoidal Bottom and Circular Bottom.