Arklow Wastewater Treatment Plant: a model infrastructure project that unblocks a town’s future

Building infrastructure is Ireland’s Achilles heel. The state seems incapable of taking it seriously to get ahead of the game. 

Despite the government setting a target of 50,000 new homes a year, the national water utility Uisce Éireann has neither the mandate nor funding to service land for growth. Neglect of investment over many decades has left the company struggling to achieve water and wastewater compliance, replace ageing and failing assets, and build resilience in the existing system – never mind plan for expansion.

The threat of swingeing fines from the European Union for non-compliance with environmental legislation offers hope the gridlock will be broken sooner rather than later. But in the meantime, squaring this circle will need creative thinking; not just from engineers, but also from urban planners and architects.

That is why the Arklow Wastewater Treatment Plant is among Ireland’s most invigorating 2020s projects. It marks the first time an architect has been a key part of a wastewater treatment plant’s design team, anywhere in the world. 

The inventive design broke a generation-long planning logjam that had stopped a vital piece of infrastructure being realised. The resulting piece of civic – not merely civil – infrastructure speaks of the public good, sets an optimistic future for Arklow and offers a model for Ireland’s urban and infrastructural development.

A history of pollution

Located at the mouth of the River Avoca, 65km south of Dublin, Arklow’s proximity to the capital has led to it becoming a commuter town, with a population of approximately 13,500. Despite its strategic location, Arklow’s growth has been curtailed by the lack of a municipal wastewater treatment plant. 

Until the commissioning of the new facility, raw effluent from the town travelled through the century-old combined sewer and drainage system. Untreated waste was discharged via sewage outfall pipes into the Avoca in the town centre, and into the coastal marine environment of the Irish Sea. The inky spume of sewage made the river and foreshore unsafe even for canoeing.

This led the Environmental Protection Agency (EPA) to classify the river and its environs as ‘seriously polluted’ in 2007. Arklow was one of four large urban areas placed on a list of 21 of Ireland’s 169 large towns not meeting European standards for effluent treatment. 

This in turn led to the EU referring Ireland to the European Court of Justice, for failure to comply with water management rules. In 1993, 1999 and again in 2005, attempts had been made to develop a suitable wastewater treatment plant for Arklow. For both financial and political reasons, none came to fruition.

In 2016, Uisce Éireann invited tenders for the design of a sewage treatment plant as part of strategic state infrastructure. Engineering design work commenced on this basis but, given the site’s prominent and visually sensitive location, the national planning board reviewed and halted the design until an architect was engaged as part of the design team to deliver a more sensitive approach. 

This was with regard to the long-term future of the lands around the site for amenity and residential use, and to allay concerns about open tanks and plant potentially restricting the town’s expansion into the port area. Dublin-based Clancy Moore Architects was added to the engineering design team following an invited competition.

Arklow Wastewater Treatment Plant: a radical rethink

The design that emerged was a radical reinvention of a typical wastewater treatment plant. The site, comprising man-made ground, likely constructed from spoil from the nearby Avoca Copper Mines, had been used as a First World War munitions plant, employing 5,000 at its peak, and latterly as a storage facility for heavy fuel oil, sodium hydroxide and nitric acid held in tanks still existing on the site. The entire area is contaminated with elevated concentrations of heavy metals including copper, zinc, lead and arsenic.

Instead of excavating to sink tanks into the site as is usually done, Clancy Moore proposed that all works be placed on the surface, avoiding the need for widescale remediation and giving the plant a unique urban presence, although much remains invisible. Some 1.8km of new tunnelling brings the town’s raw effluent to it, while the marine outfall, which was manufactured in Norway and towed to site before being precisely positioned on the sea bed, is 900m long.

The next innovation was to stack the plant processes, so that unlike a conventional plant which pumps multiple times from tank to tank, in Arklow there is only one pump lift, with the rest of the flow driven by gravity, dramatically reducing the plant’s energy needs. A roof, made for ongoing internal adjustment and periodic servicing of the plant by robotic gantry cranes, is topped with a solar farm, using photovoltaic generation to offset the plant’s energy use. 

Stacking the processes also enabled one-third of the site to be set aside for rewilding, as part of a belt of interlinked ecologies of plant, insect and bird life along this part of the coastline.

Immaculately detailed cladding

With green credentials firmly established, the architects set about slotting the plant into its context, both urban and marine. Its main functions are held in two big boxes, each veiled with a louvred skin that distributes air, assists with odour control and hides the operation of the plant from view. They have the scale of blank harbour buildings but are full of character, both from a distance and up close.

The construction is direct but refined: stubby, acid-washed, wedge-shaped concrete piers that support a bolted, galvanised steel structure, fairfaced concrete interiors, and a few flush windows facing windfarms out at sea on the Kish Bank and behind the town in the Wicklow mountains. The immaculately detailed fibre-cement cladding changes atmosphere with the passing light, both day and night, and with the temper of the sea. 

Shadowed in sunlight and drizzling water from its corrugations when it rains, it is a joyous success at every level. A small laboratory, clad in flat fibre-cement scales, holds the street like a gate lodge, waiting for a more urban future to arrive.

‘Colour mattered way more than the material choice,’ says architect Andrew Clancy, citing as one influence the sea holly that flourishes on the beach beyond the site. ‘Beauty is a thing,’ he adds, ‘but you never aim directly for it.’

Lean, green water cleaning machine

Many beautiful things fed into this design. The lab building has a faint hint of John Hejduk’s housing in Kreuzberg, Berlin, while the veiled buildings share an affinity with Herzog & de Meuron’s central signal box at Basel and the Ricola storage building at Laufen in Switzerland. The surface fixings to the corrugated sheets recall Otto Wagner’s Vienna. The architects themselves cite the influence of Hans Christian Hansen’s mid-century tectonic works in Copenhagen.

Operation of Arklow’s new lean, green cleaning machine is fully automated, staffed by a team of three engineers who are supported by remote monitoring. Its opening heralds a dramatic change in the town’s economic and environmental context, allowing it to triple in size, to 36,000 inhabitants, over the next generation, while remediating many kilometres of river, and hundreds of square kilometres of marine ecology. 

Gently radical in so many ways, this thoughtful work of architecture in support of engineering is set fair to become an essential reference for wastewater treatment plants everywhere.

Shane O’Toole is an architect, critic, curator and RIBA International Fellow

---

IN NUMBERS: 

Internal area 12,234m² 
Site area 3.2ha 
Arklow population 13,500 
Tunnelling to reach site 4km