Compare stormwater tank costs on the same scope.

What should an OSD tank cost per m³ include?

Divide the comparable cost by the usable storage volume accepted in the hydraulic design. Use net storage, allowing for the operating levels and internal displacement. Keep GST, freight, installation and exclusions on the same basis for each option.

• Tank assembly, liner or sealing system, protection and penetrations.
• Excavation, spoil disposal, dewatering, foundation preparation and backfill.
• Delivery, unloading, lifting, labour and construction access.
• Pretreatment, pits, vents, controls, pumps where needed, and maintenance access.
• Design, testing, commissioning and reinstatement.

Modular tanks versus concrete tanks

Both systems can serve a designed detention requirement. Compare the project arrangement rather than assuming one construction type will always be cheaper.

• Modular systems: review repeatable module geometry, assembly labour, wrap protection and compaction controls; maintenance is through the designed access points.
• Precast concrete: review delivered unit weights, crane access, joints, penetrations and the supplier’s structural design.
• In-situ concrete: review formwork, reinforcement, construction joints, curing, waterproofing and site programme.
• For every option: verify traffic, groundwater, uplift, foundations, durability, hydraulic operation and maintenance.

Obtain a project-based budget estimate

Send the storage volume, location, concept drawings and programme for a current supply estimate. Request supply only or a full package including module assembly and installation, and liner installation. Kontain checks the configuration, component schedule, wrap, freight, installation scope and programme before issuing an offer. No generic installed rate or percentage saving is claimed here.

Practical questions