New cell for Bennadrove Landfill

Construction of a brand new waste cell at Bennadrove Landfill has been completed.

The £2.5 million project took place on the Isle of Lewis and was implemented by Comhairle Nan Eilean Siar (Western Isles Council) – the unitary local authority for the Western Isles of Scotland. The project ran on programme with no major disruptions and reached completion in September 2012.

Approximately 30,000 tonnes of waste are produced each year on the Western Isles. Comhairle Nan Eilean Siar is responsible for collecting and disposing of all the waste throughout the Isle of Lewis with some waste material being sent to landfill and some being recycled. The new cell – Cell F – was built to increase landfill provisions at the Stornoway site, in order to meet the ever increasing demand for the service, and will help the local council to continue its important work.

Comhairle Nan Eilean Siar Waste Disposal Operations Officer, Iain Macleod, said:

“The act of landfilling will never go away. Recycling initiatives will remove a certain amount of waste from the equation but there will always be a residual amount of waste which will have to go to landfill.

“To landfill any waste it has to be disposed of within compliant and regulatory boundaries, which have been fully engineered and developed to accommodate the waste.

“Bennadrove Landfill is approximately 30 hectares in size and roughly a quarter of the site has already been developed to include various active disposable cells and closed off cells. The remainder of the site is now available for future development and this is something that we will explore when needed in time.”

Iain Macleod added:

“Cell F is a new disposable cell and was built as a continuation of the current active Cell 1E. Cell F joins Cell 1E on the north and the west side of the Bennadrove Landfill site and continues to extend the overall landfill provisions, albeit in individual stand alone cells.

“Cell F has a similar design to the previous cell, Cell 1E, with the same lining system employed once again. The aim of this project was to continue the tried and tested method and I’m pleased to say it has been a success.”

Work began on the project at Bennadrove Landfill in February 2012. Construction engineering contractors Jones Bros Ltd was the main contractor on the project, whilst local company Duncan Mackay and Sons provided most of the heavy plant used on the site. During the initial preparation work for the construction of Cell F, Jones Bros Ltd employed a 35 tonne Komastu excavator with a specialist rock-breaker attachment to prepare the site.

WYG oversaw the quality assurance aspects of the project on behalf of Comhairle Nan Eilean Siar.

Cell F comprises a mix of aggregate, an underlining drainage system and soil. At the base of the cell sits a 500 mm layer of drainage stone which is then covered with a separation geotextile membrane and a 500 mm layer of Bentonite enriched soil.

The Bentonite enriched soil was manufactured using a mix of aggregate and Bentonite powder and this layer is covered with a 2 mm thick liner of HDPE plastic. On top of the plastic is a protection geotextile membrane and this is topped off with a 500 mm layer of clean stone which is used for drainage. All of the works on the site were conducted to ensure that they were compliant with all current regulations, including the European Landfill Directive.

Towards the end of the works on Bennadrove Landfill, electronic leak detection specialists Sensor carried out work to test the water tightness of the plastic liner within Cell F. The operation involved passing an electric current underneath the cell’s liner to check for any weaknesses.

Sensor’s UK Managing Director, Jon Crowther, said:

“We’ve been in business 22 years and we got into this line of work specifically to protect the environment from any leaks that can occur from landfill sites, lagoons or mining installations. We monitor the integrity of these liners and ensure that there is no contamination to the environment.

“We have tested over 15,000,000m² of geomembrane liners worldwide and we pride ourselves on our honesty and integrity.”

Iain Macleod said:

“The construction of the new cell at Bennadrove ran fairly smoothly; there are always technical challenges, and we undertook an extensive period of testing throughout August 2012, but the completion date was reached on time.

“During the work we were able to make use of a high level of locally sourced materials which reduced the amount of materials that we had to import and this helped speed up the process.”

Iain Macleod added:

“Bennadrove Landfill is the only active landfill site in the Western Isles, covering a geographical area between the Butt of Lewis and the Isle of Barra, as well as covering all of the southern isles. On average we accept something in the order of 30,000 tonnes of mixed municipal waste along with some construction and demolition materials throughout the year.

“For the local economy this cell presents a more cost effective option than exporting the waste materials to the mainland. If we were to export waste then we would have to cross a 14 mile stretch of water via a ferry and the costs would just be too prohibitive.

“Based on the present rate of infill, the life expectancy of Cell F is approximately eight years. We will be looking to the future to extend the provisions on the site and we will more than likely repeat the exercise within six years. Although work on this site is complete for now, this is an ongoing project.”

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