| CASE STUDY


GUERNSEY AIRPORT’S groundwater quality has been enhanced by water engineer- ing specialist Trant Construc- tion, reflecting a challenging brief met by genuine working partnerships, trademark ex- pertise and proven technolo- gy. ARCADIS UK contracted Southampton-based Trant to complete the project for Guernsey


Airport, overseen


by the island’s Public Services Department.


The groundwater plant scheme involves a new drain- age system and additional pollution control measures to afford a greater level of pro- tection for the island’s water supply. The new plant will treat surface and groundwa- ter from the international air- field, before entering the Beau Valley stream to the north of the airport boundary, and help filter out traces of a toxic chemical, previously used in firefighting foam and called perfluorooctane sulfonate (PFOS).


An environmental require- ment of the Airport 2040 de- velopment, which will equip the airfield to service the is- land for the next 30 years, the work dovetailed with an £80M project to upgrade the airport’s surfaces.


The operation of the treat- ment plant was required un- der waste license to allow removal of 7,000m3 of soil


contaminated with PFOS; af- fected soil was sealed inside a container and covered with a mound of earth.


Production of PFOS began to be phased out in 2000; now concentrations in finished and semi-finished products must not exceed 10mg/kg.


With operational comple- tion and handover in March, the success of the project was achieved


through in-house


multidisciplinary teamwork and experienced site staff, with Trant’s specialist clean water engineering team lead- ing the way.


Trant worked with AR- CADIS, Guernsey Airport and Guernsey Water to ensure plant operation and tests were completed to allow closure of the airport on March 20-21, reportedly the first scheduled one, other than Christmas Day, since 1974. The scheme is designed to


filter flows of up to 20l/s by diverting these from the Lov- ers Leap outfall up to the fil- tration plant where it passes first through the anthracite filters and then through the granulated activated carbon filters before returning by gravity back to Lovers Leap and discharged to stream. ARCADIS carried out the project management and overall design, while Trant provided detailed design in- house;


anthracite pressure filters, granulated activated


carbon, process, electrical and ICA. Trant was responsible for the civil, mechanical, elec- trical installation and com- missioning. Trant Systems Electrical (TSE) designed, manufactured, installed and commissioned the new mo- tor control centre (MCC) and Treatment Control Panel (TCP), and developed the functional


design specifica-


tion and process software. Laurent Wallis, M&E pro- ject manager for Trant, says: “Trant Construction relished the opportunity to be in- volved in this interesting and challenging


project which


was subject to close media scrutiny. We have again been able to demonstrate our capa- bilities in providing complete civil, mechanical, electri- cal, design, construction and commissioning within pro- gramme.”


ARCADIS UK, which car- ried out the environmen- tal study and design for the scheme and project-managed construction, says: “Because of the client’s compressed time schedule, the specifica- tion was performance-based rather


than prescriptive.


Procurement of the bespoke process elements was always going to be extremely chal- lenging as this was where the critical path lay.


“Part-way through the


nine-month build, the client requested to have the plant functional two weeks earlier than the March 30 planned completion. This was to en-


sure that ground water would be treated when excavation started on March 20 for the ensuing


runway improve- ment contract. The challenge


was met by Trant, who made great efforts to successfully achieve this.” A site compound was first established encompassing


A high-profile groundwater plant scheme has been successfully completed at Guernsey Airport.


Planes, drains and pollution controls


10 | WET News | July 2012


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