ARCADIS UK (http://www.arcadis-
In essence, the groundwater plant scheme involves a new drainage system and additional pollution control measures to afford a greater level of protection for the island's water supply.
The new plant will treat surface and groundwater from the international airfield, 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 requirement of the Airport 2040 development, www.gov.gg/airport2040, which will equip the airfield to service the island for the next 30 years, the work dovetailed with an £80m project to upgrade the airport's surfaces.
The operation of the treatment plant was required under waste licence to allow removal of 7,000m3 of soil contaminated with PFOS; affected 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 no exceed 10mg/kg.
The success of the environment project was achieved through in-house multi-disciplinary teamwork and experienced site staff, with Trant's specialist clean water engineering team leading the way.
Trant worked closely with ARCADIS UK, Guernsey Airport (http://www.guernsey-
It was reportedly the first scheduled closure, other than Christmas Day, since 1974.
The scheme is designed to filter flows of us to 20l/s by diverting these from the Lovers Leap outfall up to the filtration plant where it passes first through anthracite filters and then through granulated activated carbon filters before returning by gravity back to Lovers Leap and discharged to stream.
Key partners on the project:
ARCADIS UK carried out the project management and overall design;
Trant Construction carried out the following detailed design in-house; anthracite pressure filters, granulated activated carbon, process, electrical and ICA;
Trant Construction was responsible for the civil, mechanical, electrical installation and commissioning;
Trant Systems Electrical (TSE) - www.t-s-e.co.uk - designed, manufactured, installed and commissioned the new motor control centre and treatment control panel. TSE also developed the functional design specification and process software.
Laurent Wallis, M&E Project Manager for Trant (http://www.trant.co.uk/)
"We have again been able to demonstrate our capabilities in providing complete civil, mechanical, electrical, design, construction and commissioning within programme.
"We'd like to take this opportunity to thank our partners and staff at ARCADIS UK for its considerable assistance and willingness to work together to successfully deliver the project to completion."
ARCADIS UK, which carried out the environmental study and design for the scheme and project-managed construction, said: "Because of the client's compressed time schedule, the specification was performance-
"Procurement of the bespoke process elements was always going to be extremely challenging 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 March 30th planned completion.
"This was to ensure that ground water would be treated when excavation started on March 20th for the ensuing runway improvement contract. The challenge was met by Trant who made great efforts to successfully achieve this."
How the mission was achieved:
A site compound was first established encompassing Lovers Leap and a section of the Airport Fire Training Ground, which was assigned landside status for ease of construction activities.
Key factors in project delivery were providing Guernsey Airport with project flexibility, continued equipment supplier support, post-contract completion (The States of Guernsey expects and requires the same level of response from suppliers as if on the UK mainland) and continued process support, post-contract completion.
Specific points related to the contract:
Trant's design team worked closely with ARCADIS UK and Guernsey Airport to ensure that the project remained on schedule and that the particular health and safety and security aspects involved with working on an international airport were adhered to.
Advanced notice was required for lifting operations.
Low visibility periods are common during the first quarter of the year on Guernsey and due to safety concerns it was necessary to suspend all works in designated areas and postpone lifting operations.
Due to Guernsey's small and busy road network it was necessary for larger items of plant and equipment to be brought in along the island's designated heavy goods route prior to 6am and across the airport runway with the assistance of airport operations.
With the largest crane on the island being 25 tonnes, and due to the layout of the filter plant, it was necessary to perform a tandem lift for each of the GAC filters.
Throughout the project Trant remained in close contact with airport operations and the control tower to ensure that sufficient notice was given of any requirements and that any safety concerns they had were dealt with immediately.