ACO takes its rooftop attenuation system underground to capture stormwater runoff

ACO Building Drainage has taken its RoofBloxx attenuation system underground to prevent flooding and water pollution at the newly extended Harbourside Car Park at Port Talbot.

Remedial works to the Port Talbot Harbourside Strategic Employment Site commenced in March 2021, with the long-term aim to redevelop Port Talbot’s docklands to help drive employment and growth.

The improvement scheme has secured £2.7m worth of funding from the European Regional Development Fund via the Welsh Government. Commissioned by Neath Port Talbot Council, the scope of the project includes remediation of former brownfield land, construction of an access road, upgrading existing highways and installing flood mitigation measures. Critical to the scheme is the extension of the Harbourside Car Park. With a capacity of 111 spaces, the car park serves many local businesses and people, as well as the nearby Parkway Railway Station.

A key requirement of the extension was ensuring an adequate drainage solution was installed that could handle intense rainfall events while carefully managing surface water runoff. However, there were some key challenges to overcome as part of this. This included cleansing water runoff of pollutants in accordance with Wales’ provisions to the Flood and Water Management Act 2010 before being allowed to re-enter waterways. As part of this, the system needed to be accessible for local authorities to inspect and maintain at later dates, while also needing to be cost effective and easy to install.

Designing a unique flood mitigation solution

Led by Port Talbot-based contractors Andrew Scott Ltd, ACO’s technical specification team was approached to help clean and capture the stormwater runoff from the car park

Due to the low level of cover and lack of depth available underground, ACO designed and specified a bespoke attenuation tank. Installed underneath the Harbourside Car Park, the company deployed an unusual solution by using its RoofBloxx range, traditionally used on rooftops to create blue roofs.

Using just over 4,000 RoofBloxx units, ACO created two attenuation tanks measuring 254m² in total, with a depth of just 295mm. Chosen because of its robust yet shallow profile, the tanks capture stormwater, before slowly releasing the water back into the waterway. The tanks also contain a bespoke filtration media that helps to remove sediment during the release of water. Lightweight yet high-in-strength, the adjustable geocellular storage solution was easy to handle and minimised installation time and labour costs.

Matthew Denniff, Regional Sales Engineer at ACO, said: “The Harbourside Car Park extension has been a one-of-a-kind project as we had to keep many factors in mind when drawing up a solution. In addition to cost and installation, we needed to consider hydraulic loading capacity, water cleansing requirements, maintenance needs and the physical footprint available.

“We recommended RoofBloxx as it met all these necessary considerations, while helping Andrew Scott’s thanks to its ease of installation and cost-effectiveness. Not only this, but we engineered a bespoke filtration system to remove heavy metals, total suspended solids (TSS) and hydrocarbons that are generated from cars.”

QuadraCeptor Cleansing

As well as the RoofBloxx attenuation tank, ACO combined two of its QuadraCeptor filtration units into the project, which remove sediment and harmful pollutants from the surface water runoff.

To also ensure that water was cleansed appropriately, ACO installed a special filtration media into the QuadraCeptors which can be easily removed and replaced. Significantly, the system achieves 0.8+ on CIRIA’s Mitigation Indices for the three main pollutant groups – TSS, hydrocarbons and heavy metals. This goes above and beyond the advised guidance given by the association under its SuDS Manual.

“Prior to our involvement, a crucial challenge facing Andrew Scott on the car park was the need to filter and cleanse stormwater, as well as being able to access the drainage solution. As sediment builds over time, filter media can get blocked, however, other solutions that were being considered did not account for entry or maintenance,” said Denniff.

“We designed the tanks so that they are easily accessible through manhole covers, meaning the filter could be removed and replaced during future maintenance schedules. The entire system is combined into one unit, and by following the SuDS Manual, we have met the guidance and requirements set out by approving bodies and Welsh law.”

Mark Reece, Site Manager at Andrew Scott, said:“ACO has come up with a solution that not only met all the necessary requirements, but they’ve also value-engineered the project through their innovative use of RoofBloxx. We are very pleased with the service from the ACO team. Their knowledge and experience have been invaluable and the attention to detail has been exceptional, from the design and consultation through to being on-site to help oversee installation.”

From start to finish, the installation of the RoofBloxx attenuation tanks at Port Talbot Harbourside Car Park took just under a week and the car park opened to the public on 18th March 2022.



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