--- title: "SuDS and Drainage Design" description: "Surface water, foul drainage and watermains designed to council SuDS policy and Uisce Éireann standards." updated: "2026-10-12" url: "https://www.petruf.ie/services/civil-engineering/suds-design" --- # SuDS and Drainage Design > Surface water, foul drainage and watermains designed to council SuDS policy and Uisce Éireann standards. Every new building has to deal with the rain that lands on it. Councils now expect most of it to be held, cleaned and soaked away on the site, with pipes and tanks as the last resort rather than the first. Kildare's development plan requires SuDS on all new development, down to a single house, and the Dublin councils ask the same through their own guides. A design is judged on three things: how much rain is held, how fast the rest is let go, and who maintains it. We design the surface water, the foul drainage and the watermain on the same drawings as the levels and the foundations, carry out the soakaway tests on the site, and run the Uisce Éireann applications from the pre connection enquiry to the network being taken in charge. ## What we design ### SuDS measures Swales, rain gardens, filter drains, tree pits and green roofs, chosen for the site and sized for the storms it has to take. ### Permeable paving Driveways, parking and footpaths that store rain in their own build up and let it through. ### Soakaways and infiltration Infiltration tests carried out on the site to BRE 365, and soakaways sized from the rate the ground actually gives. ### Attenuation and flow control Storage and a flow control that hold the discharge to the greenfield rate, where infiltration alone cannot. ### Surface water networks Pipes, manholes and outfalls with falls that work against the finished levels. ### Foul drainage Wastewater networks kept separate from surface water, to the Uisce Éireann Code of Practice and standard details. ### Pumping stations Foul and surface water pumping stations where the site cannot drain by gravity. ### Watermains Water supply layouts with the valves and connections Uisce Éireann will take over. ### Uisce Éireann applications Pre connection enquiries, confirmation of feasibility, design submissions and connection applications. ### Taking in charge Drawings and submissions for the council and Uisce Éireann to take the drains, the mains and the roads over. ## What the council will check These are the figures a surface water design is held to across most of Ireland. Each council sets its own, and they are agreed with its drainage section before the design is fixed. ### Interception: The first 5 mm of rainfall held on the site, 10 mm preferred, so it never reaches a drain The Greater Dublin Regional Code of Practice for Drainage Works, applied well beyond Dublin. ### Discharge rate: No faster than the greenfield runoff rate, QBAR from IH124, with 2 l/s/ha as a practical minimum The GDSDS, and council development plans. ### Climate change: 10% added to rainfall in the GDSDS; most councils now ask for 20%, some 30% Agreed with the council's drainage section for each site. ### Infiltration: Soakaways sized from an infiltration test on the site BRE 365, required by planning condition. ### Attenuation tanks: A last resort, where surface and nature based measures cannot do the job Kildare and South Dublin SuDS guidance. ## What you receive Drawn to what the authority will take in charge, not to what fits the site plan. - A SuDS strategy, and the surface water report the planning application needs - Infiltration test results and the soakaway design - Drainage layouts and long sections for surface water and foul - Attenuation and flow control calculations, with the climate change allowance shown - The watermain layout - The Uisce Éireann pre connection enquiry and design submission - A maintenance plan for the SuDS, and the response to any further information request ## From our projects ### [Ardbrae Park](https://www.petruf.ie/projects/public-infrastructure/ardbrae-park) Surface water, wastewater and the watermain network for twenty nine houses, drawn to what the authority will take in charge, with the Irish Water pre connection enquiries and diversion applications. ### [Mill Lane Development](https://www.petruf.ie/projects/public-infrastructure/mill-lane-development) Storm water and wastewater design, internal roads and utility connections for four houses beside a protected structure in Naas. ## The questions that come first ### Is SuDS mandatory in Ireland? No national law requires it, but development plans do. Kildare requires SuDS on all new development, down to a single house, and the Dublin councils require it through their plans and guides, so in practice it is part of almost every application. ### What is the greenfield runoff rate? The rate the site would drain at if it were still a field. Councils usually limit discharge from a development to it, worked out as QBAR with the IH124 method, with about 2 l/s/ha as the lowest rate a flow control can practically hold. ### What is interception storage? The first 5 mm of every rainfall, 10 mm preferred, held on the site so that it never reaches the drain or the river. It is the dirtiest part of a storm, and soaking it into the ground or the planting is what keeps it out of the watercourse. ### Do I need a soakaway test? Yes, wherever water is to be soaked into the ground. The test is done on the site to BRE 365, usually in the position of the soakaway, and the rate it gives decides whether infiltration works at all and how big the soakaway has to be. Councils commonly make it a condition of permission. ### Are attenuation tanks still allowed? Only as a last resort. Kildare and South Dublin both ask for surface and nature based measures first, and a tank has to be justified by showing those cannot hold the water the site produces. ### What is a Confirmation of Feasibility? Uisce Éireann's answer to a pre connection enquiry, saying whether and how the development can connect to the water and wastewater networks. It usually takes around sixteen weeks and goes in with the planning application, so the enquiry is worth making early. ### Who maintains SuDS once they are built? The owner or the management company, until the council takes the scheme in charge. A maintenance plan saying what is inspected, cleared and replaced, and how often, is commonly asked for with the application.