Alderney airport plans facing scrutiny

Wednesday 24 January 2024

The proposed work to extend and rebuild Alderney's runway and airport could have a "significant environmental effect" on the island's water environment according to a new report.

An Environmental Statement - required as part of the multi-million pound Alderney Runway Rehabilitation Project - has been published, with chapters on the Environmental Impact, Climate Change, the island's Socio-economics and Agriculture, Water and other considerations.

Back in December 2022, the States of Guernsey agreed the multi-million pound plans to redevelop the runway and airport but it was also agreed that an ‘Full’ Environmental Impact Assessment (EIA) would need to be carried out before any work could begin.

The plans include extending Alderney Airport’s runway to the west and to reconstruct or refurbish the Terminal Building and Fire Station so that larger aircrafts can use the runway. 

The size of the area to be affected by the planned building work is approximately 30.9 hectares.

Pictured: The red outline shows the proposed expansion and extensions to the airport and runway in Alderney.

The EIA found no significant effects were expected to arise during the actual construction phase of the planned development around the airport and runway but there is one major concern for the island's water quality once the new airport and runway are in use.

The EIA found there could be problems caused as a result of the potential need for de-icing on the larger aircraft which will then be able to fly in to the island. 

The work to de-ice ATRs could have a 'Major Adverse and Significant effect' on the 'potential change in water quality of the Bonne Terre Stream' which is the destination for water run off from the airport. 

The EIA says that "the biodegradation of de-icers results in the consumption of very high amounts of dissolved oxygen. As the Bonne Terre Stream is relatively small there is likely to be insufficient flow to dilute the de-icer contaminated runoff from the Airport, which is likely to constitute a significant proportion of the flow. This would result in a seasonal but significant adverse impact on the Bonne Terre Stream, the online ponds downstream, and potentially the small wetland area close to Platte Saline".

This is not a risk at present because of the lesser need to de-ice the smaller planes which currently service Alderney.

Against the perceived risks from de-icing, mitigation is proposed in the form of a De-icing Management Plan and a Drainage Strategy which would minimise the effect caused by the larger aircraft. 

The management plan would include a water quality risk assessment to estimate what chemicals could enter the water run off systems through de-icing, and how it can be reduced.

The Bonne Terre Stream’s water quality and flows would also need to be monitored along with aquatic ecological surveys "to better understand the sensitivity of the watercourse and associated water features (namely the online ponds and the wetland near Platte Saline)".

Following the risk assessments it may be decided that the water run off should be discharged a different way - avoided the Bonne Terre Stream. But, if no alternative can be found then de-icing of aircraft and the airfield might not be possible at Alderney Airport.

However, if a solution can be found then a De-icing Management Plan would focus on the procedural use of de-icing chemicals and in particular how it is managed by Alderney Airport and the Alderney Water Board to ensure that no water is taken from the Bonne Terre for human use when de-icer has been used.

The full Environmental Impact Assessment can be read HERE.