Why Engineers are moving away from specifying concrete stormwater tanks

Engineers often avoid specifying concrete stormwater tanks where site conditions, performance requirements, cost, and constructability create unacceptable risk or costly delays.

Concrete’s weight, rigidity, curing time and susceptibility to cracking, leaching and chemical attack make it less suitable in corrosive or reactive soils, high groundwater conditions, tight or obstructed sites, or projects with accelerated programs and limited access. Concerns around watertightness, long-term durability, maintenance, sustainability and water quality further reduce its appeal—particularly for reuse applications—leading designers to favour lighter, modular alternatives that offer faster installation, higher chemical resistance, flexibility and lower whole-of-life cost.

In a recent webinar held through Engineers Australia, the question was asked

An independent report by Rider Levett Bucknall found that modular, precast, and cast in situ concrete tanks involve high transport, craneage, labour, and curing costs, making them more complex and expensive to install.

To learn more, click here

In what applications would you not specify concrete tanks and why?

Here are some of the responses

—————————————————————————————————————————————————————————————————————-

Concrete tanks may be unsuitable for underground stormwater detention or reuse where watertightness, water quality, and long-term durability are critical. In corrosive soils, high water tables, or areas with tree root intrusion, HDPE or modular systems offer superior chemical resistance, joint integrity, and installation speed. Concrete mass, curing time, and vulnerability to cracking under cyclic hydraulic loads increase maintenance demands and risk leakage.

Non-concrete systems often deliver longer design life with lower lifecycle maintenance, especially where access is limited. For reuse applications, material inertness and minimal biofilm buildup are essential—criteria where concrete may underperform without costly coatings or upgrades.

Azin A

Avoid cast in-situ concrete tanks where construction time is limited, site access is tight, excavation depth must be minimised, or ground conditions are variable. Their rigid walls, heavy mass, curing time, and sensitivity to reactive soils, heave and groundwater pressures make them unsuitable on constrained or movement-prone sites, and they require confined-space maintenance.

Avoid precast concrete tanks where crane access or laydown space is restricted, where irregular footprints or services must be navigated, or where reactive soils cause differential settlement. Precast units are heavy, less adaptable, and require uniform bearing support that such sites cannot provide.

Brendan M

I would not specify concrete tanks for applications where budget is a primary concern, site access is limited, flexibility is needed, or the stored substance requires high purity without potential leaching. Other materials like plastic or steel are better for these scenarios due to lower costs, easier transportation and installation, greater flexibility, and inherent chemical inertness that prevents unwanted reactions or contamination. I would definitely consider Stormbrick’s Geocellular tanks for these scenarios.

Derick C

Concrete tanks are generally avoided where their weight, construction logistics, or material behaviour create engineering issues. They are unsuitable on low–bearing-capacity or highly reactive soils, or in high-corrosion or acidic/alkaline environments without costly liners.

Sites without water tables may also favour lighter materials. Where cranage limits, restricted access, or tight programs exist, HDPE or coated-steel tanks offer better chemical resistance, flexibility, faster installation, and lower whole-of-life cost.

Oliver J

Concrete tanks should be avoided in applications with tight time constraints requiring rapid installation, in temporary works that need frequent relocation, and in areas with poor ground bearing capacity that cannot support heavy structures.

Concrete tanks are also unsuitable without protective coatings in highly corrosive environments or for storing chemicals, as their porous structure can allow chemical penetration and lead to reinforcement corrosion.

Rangana L

I would not specify concrete tanks in the following scenarios;

Corrosive or aggressive soils/water conditions as concrete is prone to degradation
Budget constraints apply. For example, ACO StormBrixx offers up to 62% cost savings over cast in-situ concrete
Restricted access or tight sites make large excavation and crane lifting impractical
Fast installation is critical since concrete requires in-situ curing which can cause delays
Sustainability goals are a priority, due to concrete’s high embodied carbon

ACO StormBrixx is lightweight, hand installable, quick (no curing), adaptable for detention/reuse, and resistant to chemical attack which is ideal for constrained or environmentally sensitive projects.

Tegan B

ACO. we care for water