Background to specification
Tubosider has provided a number of large stormwater attenuation systems to Dublin Airport airside for its terminals and aircraft aprons in recent years.
Jons Civil Engineering of Duleek are among a number of Irish contractors who propose the use of Tubosider’s unique loadbearing systems, this time for the R132 road improvement project between the Airport roundabout and Collinstown Cross.
Besides converting the 1.3km (1420 yard) road from a single to dual carriageway with bus lanes, cycleways, footpaths and verges, the contractors were to also install a new strictly controlled attenuation system.
From the start, JCE’s project management team liaised closely with Tubosider’s technical sales and design teams to produce a system which complies not only with the SuDS concept, but also the Greater Dublin Strategic Drainage Study. Drainage had to be carefully integrated into the site while taking account of original greenfield drainage patterns.
JCE’s John Killen explains how the attenuation element came to be specified:
“The attenuation tanks are a contractor designed element, and the employers’ specifications were performance based. We found that the Tubosider product was the most suitable on this project for several reasons.
“These included overall cost, the quality of support from the Tubosider design team, and the fact that they and their products are familiar to the client, as they had previously used them on the same drainage network in the airport. That and the follow up support and post installation inspection they provide.”
The Tubosider design, in this case using a Twinstore system, was also the most efficient in meeting the challenges posed by the confined plan area of the site and because the outfall levels to the stream limited the options available.
By choosing Twinstore’s exclusive and patented space-saving solution, balancing the volume of rainwater captured between unsealed tanks and a lined aggregate fill, the whole attenuation footprint was limited to just 22 x 53.5 meters.
Solution & benefits
Edge of road drainage into local streams has now been replaced by a kerb and gulley system with carrier drains combined with filter drains through pollution controlled attenuation tanks to a designated outfall point.
The design consists of two Twinstore tanks, one with a 1685 cubic metre capacity in 1800mm steel pipes and one of 585 cubic metres in 1600mm. Using two diameters also allowed all the prefabricated sections to be nested when transported from St Helens, thus saving considerably on cost and time.
The same environmental approach previously proved a massive advantage in delivering Tubosider’s biggest yet tank to Dublin Airport in 2008. That time, the number of flatloaders to deliver the 15,600 cubic meter tank was effectively halved, saving over 200 journeys.
“The design input was excellent from the first, with Tubosider taking a holistic approach to the attenuation requirements and drainage design as a whole,” says John Killen.
“The integrated flow control system avoided the need for secondary suppliers and saved the construction of additional flow control manholes. Designing with separate size pipes for the two tanks we required greatly reduced the delivery cost, and made their bid the most economically and environmentally efficient.
“We have used their quotes as part of previous tenders, but this is the first occasion that we have been awarded a project that required attenuation in a confined design. I found the Tubosider management team very easy to deal with and technically very competent and genuinely interested in the drainage and attenuation design.
“What’s more, the product is very easily installed and robust for site handling. We would have no reservations in engaging with them on future projects.”