How does cellular storage work for stormwater control?

Certain stormwater controls are designed in ways that effectively divert water away from a site – but not cellular storage systems. Sometimes also called geocellular systems, geocellular attenuation tanks, or soakaway tanks, these Sustainable Drainage Systems (SuDS – aka LIDs/BMPs/WSUDs) capture stormwater in large underground containers for slow release. But why utilize a stormwater control (SWC) method that simply captures the water and slows it down, rather than diverting it? Let’s explore cellular storage.

Why engineers use cellular storage for stormwater control

As cities continue to grow and expand, traditional drainage systems often struggle to cope with the increased volume of runoff. Cellular storage offers a practical and effective method to manage stormwater by providing underground storage that allows for gradual infiltration into the ground or controlled release into a drainage system.

Cellular storage systems are composed of modular plastic units that can be easily assembled to create a highly porous structure, often in modular, honeycomb-shaped design blocks. These units are typically buried underground, creating a large void space that can temporarily store significant volumes of water during heavy rainfall events. The stored water can then either infiltrate into the surrounding soil or be released slowly to reduce the risk of flooding and erosion. They can function as either soakaways to slowly infiltrate into the surrounding soil or utilized as storage tanks for retention. This approach not only helps manage stormwater but also promotes groundwater recharge and can help improve water quality. They can be engineered to be load-bearing for pedestrian and vehicular traffic.

As you might be able to guess, having the ability to quickly store a large amount of stormwater can be vital in times of heavy downpour. So, as you’re thinking about implementing cellular storage in your drainage design, what are the pros and cons of these SWCs?

Benefits and downsides of cellular storage

Looking at the upsides of cellular storage, they mainly focus on this SuDS capability to handle large amounts of water quickly.

The key ‘Pros’ to geocellular storage are:

• Efficient space utilization: One of the primary advantages of cellular storage systems is their ability to utilize underground space, making them an unobtrusive solution for urban areas where surface space is limited. Typically, they provide around 96% of void space for water retention or detention.
• Flexibility and scalability: Cellular storage systems are highly flexible and can be easily scaled to meet the specific needs of a project. Their modular design allows for customization to fit different site conditions and storage requirements.
• Dual-use, cost-effective, durable: These can be utilized for either retention or detention. They are also one of the most cost-effective options when compared to traditional drainage systems. They can potentially last a long time.
• Enhanced water quality options: The simplest versions may not offer much water quality enhancement. However, if you incorporate features like silt traps or treatment systems, it can help filter out pollutants and improve the quality of the water that eventually reaches natural water bodies.
• Flood mitigation: These systems are effective in reducing the risk of flooding by temporarily storing stormwater and controlling its release, thus preventing the overwhelming of drainage systems during heavy rain events.
• Groundwater recharge: Cellular storage promotes the natural infiltration of water into the ground, which aids in replenishing groundwater levels and maintaining the natural hydrological cycle.

However, as with all things, in certain scenarios there can be too many downsides to implement cellular storage systems. These largely orient themselves around the initial installation cost, maintenance requirements, and the structural integrity of the system.

The ‘Cons’ of cellular storage are:

• Maintenance requirements: Cellular storage systems require regular maintenance to ensure they remain effective. This includes inspections, cleaning, and occasional repairs to prevent blockages and maintain functionality.
• Initial installation costs: The initial cost of installing a cellular storage system can be relatively high compared to traditional drainage solutions. However, this cost is often offset by the long-term benefits and reduced flood damage.
• Structural integrity: Ensuring the structural integrity of the system is crucial, especially in areas with heavy traffic or load-bearing requirements. Proper design and installation are essential to prevent collapse or damage.
• Soil and site conditions: The effectiveness of cellular storage systems can be influenced by the soil and site conditions. Poorly draining soils or areas with high groundwater levels may require additional design considerations.

Utilizing SuDS in InfoDrainage

So, how do drainage designers decide when they can implement cellular storage systems and when they can’t? How do they calculate whether a proposed system will be able to effectively handle deluges of stormwater? They use an analysis tool like InfoDrainage.

InfoDrainage is a comprehensive software solution designed to aid engineers and designers in creating effective and sustainable drainage systems, including SuDS like cellular storage. The software provides a range of tools and features to support the design, analysis, and optimization of drainage systems, ensuring they meet regulatory requirements and performance standards.

InfoDrainage supports the design of SuDS in many ways:

• Design flexibility: InfoDrainage allows users to design custom cellular storage systems tailored to the specific needs of their projects. The software supports the creation of detailed 3D models, enabling precise planning and visualization.
• Hydraulic analysis: The software includes advanced hydraulic analysis capabilities, allowing users to simulate the performance of cellular storage systems under various storm events. This helps in assessing the capacity and effectiveness of the design.
• Regulatory compliance: InfoDrainage ensures that designs comply with local and national regulations by providing built-in guidelines and standards for SuDS. This helps streamline the approval process and ensures designs meet necessary requirements.
• Optimization tools: InfoDrainage offers optimization tools that assist in fine-tuning designs for cost-effectiveness and performance. Users can evaluate different design scenarios and select the most efficient solution.

Cellular storage is a vital component of modern sustainable drainage systems, offering numerous benefits for urban stormwater management. While there are some challenges to consider, the advantages often outweigh the downsides. With the support of advanced tools like InfoDrainage, engineers and designers can effectively implement and optimize cellular storage systems to create resilient and sustainable urban environments.

Design your own cellular storage

• If you’re already an InfoDrainage user, our support docs can help you set every detail of your cellular storage system like inlets, outlets, soil type, infiltration rate, and pollution.
• Watch the Designing Cellular Storage section of our free Understanding SuDS design course.
• Grab a copy of our free Guide to Representing SuDS in InfoDrainage in accordance with the SuDS Manual Ciria 753.
• Want to try InoDrainage? We offer a 30-day free trial with no credit card required. Are you a student or educator? If so, we have some very good news for you.