This document is the 511B Installation Water Quality Unit WQU Backfill and Final Cover Detail. It shows details for backfill and final cover & riser extensions.

The backfill around the unit and by-pass detail shows the WQU outlet side, HDPE bypass pipe and tips to ensure backfill between unit, bypass and continue with Class I material per ASTM D2321 and match inverts.

Notes state that continue with Class I material per ASTM D2321 to 12” above water quality unit. Also, fill unit with water to the top of the sediment weir plate once backfill is placed and compacted 12” above the unit.

The final cover and riser extensions detail shows the finished grade, nyloplast H-25 solid cover, nyloplast in-line drain and a tip to provide a concrete collar extending at least 12” around grates/frames for traffic loading conditions.

Notes state to follow the installation guidelines and all risers extensions to grade should be coordinated with an ADS representative. Non-traffic loading and traffic loading clarification included.