Yes. For below-ground installations Viking can supply suitable trafficable or light-duty covers and risers.
Below-ground tanks have their own backfill requirements. Thin skin tanks must be surrounded with concrete — trade waste guidelines require a minimum 100 mm thickness to walls and base — and the tank must be supported internally to prevent the walls collapsing while the concrete is poured. Paneltim® tanks may instead be surrounded with crushed rock and/or stabilised sand, following the Viking Below Ground Paneltim® Tank Installation Guidelines.
Whether above or below ground, position the trap for easy and frequent access, since the basket needs emptying regularly. Provide adequate pipe fall and ventilation in accordance with AS/NZS 3500 and local plumbing codes.