Since the late 1980s, the Irish town of Arklow, about 90 minutes south of Dublin, has struggled to build a wastewater treatment plant, but delays and setbacks slowed development of a facility. Before the project was finally commissioned in 2025, raw sewage was discharged directly into the River Avoca and the Irish Sea.

The $150-million project was built on a constrained brownfield site, bordered by a working harbor, residential areas and the Nineteen Arches Bridge, built in the 1750s and a heritage landmark as Ireland’s longest handmade stone arch bridge. Project owners chose not to build a conventional plant and enlisted architectural firm Clany Moore to design structures covered with rooftops and facades.