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10.5.3 Backfilling a wet site:
Refer to backfill specification appropriate for site conditions
•
Ballast* the plant by filling each chamber with clean water to a depth of 300mm and recheck
the pipe work levels. Commence backfilling evenly around the tank ensuring that there are no
voids. Continue filling the chambers whilst backfilling, ensure that the progressive water level is
no more than 300mm above the backfill level.
•
Backfill with concrete until it has reached the invert of the outlet pipe.
•
Continue backfilling with gravel as per 10.6.1 until has reached 50mm over the cylindrical body
of the tank.
•
Mount and seal manhole extensions (if used)
•
Complete backfilling with topsoil up to the max ground level line.
* Ballasting the plant is important to avoid the tank from lifting when backfilling
