Early involvement in Guernsey’s airport runway refurbishment has enabled contractor Lagan Construction to save the client money while helping it tackle the challenges of working on an island.
A fleet of 15 John Deere tractors with specially built trailers has been circuiting Guernsey for the past 18 months, transporting imported aggregate. Every trip has travelled the same specified anti-clockwise route around the island to supply a major refurbishment project at Guernsey Airport.
Flights in and out of Guernsey number up to 200 every day - mostly turboprop aircraft
flying between the island and London’s airports.
Reconstruction of Guernsey’s runway may seem a minor affair in comparison to projects at larger airports, but Guernsey’s airport is a lifeline for the island and its inhabitants.
Refurbishment of the runway, aprons and taxi-ways on Guernsey has been planned and executed in every bit as much detail as bigger schemes of the same kind. Furthermore, the airport’s location has given the project its own characteristics and demands rarely encountered on the mainland.
Principal challenges have included the problem of how to get materials to the site. Guernsey has a single granite quarry whose annual output amounts to less than one third of the aggregate required for the island’s airport scheme, which has also needed large quantities of limestone and other raw materials for renewing the asphalt runway, taxiways and concrete aprons.
Roads on the island have a restricted width of 2.3m and a weight restriction of 8t per axle. For contractor Lagan Construction, this called for a bespoke fleet of vehicles and detailed traffic management plans for all vehicle movements.
“The greatest challenge of this project has certainly been the logistics involved,” says Lagan Construction project manager Steve Turner.
“We’ve needed over 300,000t of aggregate, built around 20km of new drainage and installed 120km of ducting, all of which has been imported by sea.”
“We’ve needed over 300,000t of aggregate, built around 20km of new drainage and installed 120km of ducting, all of which has been imported by sea”
Steve Turner, Lagan Construction
At the start of the project, Lagan Construction spent about a month building a temporary quay for docking and unloading a fleet of barges chartered to transport aggregate from Plymouth and Glensanda in Scotland.
“We also had a workforce of 150 to accommodate, 70 items of plant and 6,000t of bitumen and some 2,000 containers to import and transport to site,” says Turner.
Guernsey Airport has undergone a complete rebuild of just about everything airside, including the airfield’s drainage system and ground lighting, through a £56M contract between Lagan Construction and the States of Guernsey.
Work started on site in March 2012 and is on course to finish before the end of this year - about six months ahead of schedule.
The airport’s runway has been reconstructed to smooth out its longitudinal profile and improve its crossfalls to bring both into line with international aviation standards. At the same time, the whole 1463m long structure has effectively been shifted 120m to the west to create enhanced runway end safety areas (RESA).
“The runway remains on the same axis, but it now has enlarged RESAs at each end and a flatter profile. We’ve done a lot to strengthen and future proof the airport for heavier aircraft. We have the same target market, but have been aiming to get previous restrictions on aircraft lifted,” says Guernsey Airport director Colin Le Ray.
Sight lines along Guernsey’s runway were previously affected by a significant dip, which has been addressed by lowering one end of the runway and infilling a 300m section by up to 1.6m.
“We had a workforce of 150 to accommodate, 70 items of plant and 6,000t of bitumen and 2,000 containers to import and transport to site”
Steve Turner, Lagan Construction
Prior to the award of the contract, value engineering took place based upon proposals suggested by Lagan Construction within the tender. These saved in the region of £3M.
“The majority of this saving was made by adjustments to the phasing of reconstruction of concrete apron areas. We value-engineered 14 phases down to six, which meant more than one area could be taken out of commission at a time and produced a big cost and time saving,” Turner says.
Value engineering of apron pavement construction has helped the project score highly on sustainability, Turner says. All of the existing pavement broken out was reprocessed and used as type 1 material, saving around 60,000t of virgin material.
“The stabilised foundation also saved about 12,000t of type 1, and in certain locations a composite construction allowed for a reduction in the more expensive bituminous layers,” says Turner.
All of the runway reconstruction work has had to be done piecemeal and, with the exception of four two-day runway closures, during nightly possessions of the runway between 9.30pm and 5.30am.
“The only way this reprofiling could be done was by gradually bringing up the levels with layer upon layer of HDM asphalt 60mm to 70mm at a time,” says Le Ray. “The HDM also had to be appropriate for use as a runway surface in a temporary condition, achieving minimum friction values. Every morning, all of the runway edge lighting and white lining had to be reinstated and inspected before the runway was returned to use.”
The Guernsey Airport and Lagan Construction team also had to be prepared for getting the runway back into use much quicker, in the event of an emergency medical evacuation from the island.
“This tends to happen on average about once every month. Guernsey’s hospital doesn’t have a full range of specialist medical support so medi-vacs are needed frequently and they have to be operated by fixed-wing aircraft. We have to be able to get the airfield back operational for a medi-vac within two hours’ notice,” Le Ray says.
For Lagan Construction, readiness for such events has meant having more asphalt in hot storage than would otherwise be needed.”If we get notice of a medi-vac on its way, everything has to focus on getting any holes refilled and the runway and its lighting systems returned to use. The additional material and work represents a considerable cost but was a risk we were able to predict fairly well and take into account in tendering for the contract,” says Turner.
Given the importance of safety and security at airports, it can be imagined that operational handovers between the airport and its contracting team are also a vital part of medi-vac procedures. According to Le Ray, this is done to a tightly controlled process.
“The emergency handover process is just one of a whole series of operational procedures related to the contract planned in advance and audited by the Civil Aviation Authority to show all is being done in a very well managed manner. The work has progressed without a single significant incident thus far,” says Le Ray.
Guernsey Airport’s refurbishment scheme has been planned in line with the Construction (Design & Management) regulations despite Guernsey not being under the remit of European Union law. Consultant RPS is the designer and contract project manager, while consultant TPS is the client’s project manager.
“The level of planning enacted on this scheme stands out as exceptional,” says RPS design director Jonathan Green.
“Preparedness on an immediate horizon has been achieved through weekly meetings, allowing all to put necessary management controls in place. Daily morning meetings look at the previous 24 hours’ progress and adjust plans for the following day accordingly.”
Planning constraints on Guernsey Airport’s refurbishment have been sufficient to ensure that every one of the airfield’s relocated approach lights is now supported on camouflaged poles. The airport is adjacent to a number of private properties and the construction environment management plan for its refurbishment has centred heavily on managing noise and light levels.
“This is usually a very quiet island,” says Le Ray. “The expectation has been a background level of 39dB at night, with a restriction of never exceeding this by 10dB and a requirement to take measures to reduce noise if the limit is exceeded by 5dB.
“Vehicles are not allowed to pass schools during peak hours. They have to travel on a designated route at specified times and seek permission if they want to deviate from it. This creates a 20km round trip instead of an 8km direct route, but it’s been the only way of getting such large quantities of material to site with minimal disruption for the island.”