This document is the 511 Installation Water Quality Unit WQU Trench and Placement Detail. It shows details for preparation, placing and backfill for the unit.

The trench and bedding preparation for unit detail shows the dimensions, undisturbed earth and Class I material per ASTM D2321.

Notes state to avoid excessive ground water in trench, provide sheeting or shoring as required, maximum cover height measured from top of the unit to final grade and shall not excess 8”, modified trench bottom required if soft or rock material is found. A table with unit size and minimum D & W diameters is shown.

The placing unit and initial backfill detail shows the access riser, storm water quality unit inlet side, Class I material per ASTM D2321 backfill to bypass OD invert compacted, 6” bedding, set storm water quality unit on line and level and leave area open to set sump inlet TEE.

Notes state to utilize care when lowering unit into the trench, place backfill around unit in uniform 8”-12” lifts, compacted and when the unit consists of 2 sections, place the downstream section first. Properly lube the bell and spigot then connect and home the remaining pieces.