Generating energy for the future

A Dublin waste-to-energy project required a comprehensive belowground protection solution

A full range of belowground waterproofing technologies from GCP Applied Technologies is being installed to provide comprehensive long-term protection against corrosive ground water, coastal soil conditions and ground gases at the new incinerator plant in Dublin, which will provide sustainable energy from waste to the region.

Located in Poolbeg in Dublin Port, the Dublin Wasteto- Energy project due to complete construction this autumn will generate energy from up to 600,000 tonnes of municipal waste every year powering up to 80,000 homes. The 30,000m2 footprint incinerator plant has had its belowground areas fully protected against water and ground gas with a fully engineered continuous system which features a range of solutions designed to work together from GCP. These include high performance Grade 3 waterproofing solutions for habitable areas and systems to prevent ground gas ingress.

The Dublin Waste-to-Energy project, a Public Private Partnership (PPP) between Dublin City Council and Covanta, a world leader in sustainable waste and energy solutions, will also provide district heating for up to 50,000 homes. The project comprises a substantial waste reception hall and two adjacent stacks of 100m in height, and represents an investment of approximately €500m by Covanta in sustainable energy for Ireland.

The combined need to address potential radon and other ground gases on the site with a variety of waterproofing protection made this an ideal project for a fully compatible below-ground waterproofing system from a single source. Engineers and architects at PM Group specified GCP as a recognised global solutions provider in the sector with proven products, which could deliver a continuous solution for a project of this prestige and profile.

The specifiers developed a close working relationship with GCP and project contractor PJ Hegarty and Sons, which was invaluable in identifying and installing the successful solution. PJ Hegarty and Sons are widely recognised in the industry for their expertise and precision in construction and benefitted from the specialist knowledge, which GCP was able to bring to the table. A GCP-trained specialist applicator ensured that best practice installations would be carried out.

The solution installed
All habitable areas of the concrete substructure including offices were specified with the Preprufe® 300R PLUS membrane system to provide Grade 3 waterproofing under BS8102:2009. Preprufe is an advanced membrane system which offers the safest and most reliable waterproofing option available for below-slab waterproofing. Designed with synthetic adhesive layers, the patented Advanced Bond Technology™ enables concrete to aggressively adhere to Preprufe, forming a unique intimate seal that prevents water migration between the waterproofing and the structure, substantially reducing the risk of leaks.

The product also protects substructures from the harmful effects of water, vapour and gas and can be applied to wet or dry concrete. It is immediately trafficable after a fast installation, which helps shorten project timescales. Preprufe 300R PLUS also provides an effective barrier against ground gas to meet radon protection requirements, offering further benefits for habitable areas of the Dublin project.

The larger non-habitable areas located under the footprint of the incinerator itself were specified with the loose-laid GCP Gas Membrane. This high performance, reinforced polyethylene damp proof membrane incorporates a gas resistant aluminium foil making it radon, methane and CO2- proof. Its multi-layered laminate structure provides strength, flexibility and installation properties.

Ancillary products used for detailing ensured the continuity of the waterproofing between the building’s foundation and the pile heads and these included Bituthene® LM and Bituthene 4000. Designed for speed and ease of detailing they were critical to maintaining an efficient programme.

Adcor® 500S, a rubber (hydrophilic) waterstop strip that expands upon contact with water was placed in construction joints and fixed with Adcor Adhesive/Mastic. When fully encapsulated by poured concrete, the strip’s expansive forces form a seal against concrete faces.

Finally, Preprufe 800PA cold-applied self-adhesive waterproofing membrane was applied to the walls of the superstructure where the access ramp for waste trucks enters the waste reception hall. Preprufe 800PA is composed of a reinforced cross-laminated HDPE film and a synthetic nonbituminous adhesive. Like the Preprufe 300R PLUS system, Preprufe 800PA incorporates Advanced Bond Technology. The access ramp will also feature Silcor® 900S sprayapplied seamless waterproofing which rapidly cures to form a high-strength, elastomeric, and fully bonded waterproof protection.

Other challenges addressed by the Preprufe waterproofing solution on this project include the coastal soils that contain sulphates and chlorides and can compromise concrete belowground structures and affect watertightness and durability. Rebar corrosion is also common, resulting from chloride ingress from airborne salts or belowground chlorides. Products also had to be durable enough to cope with winter application, and tough enough to withstand a large volume of reinforcing steel placed upon them. GCP Protection Boards were used to protect the membranes during construction.

Business Development Manager at GCP, Ireland, Leslie Trayer comments: “Preprufe has been specified successfully for over 21 years, mainly for basement construction. As experts in protecting major belowground structures we assisted PM Group in not only explaining what level of protection they would require in all areas of this innovative and important project, but also delivering the ideal waterproofing solution for the location to provide durability during construction and whole-life performance.”