Timber
The use of tropical hardwood will inevitably cause concern to those of you who are worried about global warming and its effects – and quite rightly so.
515 cubic metres of Ekki for the groyne piles and planks are coming from Cameroon, along the Gulf of Guinea, Central‐West Africa.
Forestland covers almost half of the country’s total land area, some 51.8 million acres (21 million hectares). Cameroon’s forests represent the northern limit of the Congo Basin’s forests, the second largest contiguous rainforest in the world, after the Amazon. The map below shows the vegetation of Cameroon and all of it is forest except for those parts coloured blue, pink, orange and beige. Our timber is coming from Wijma UK Ltd which has a full FSC certified chain of custody.
Enlarge Map
“Cameroon’s forests forms part of the second largest contiguous rainforest in the world, after the Amazon.”
Rainforest Alliance, 2014
Ekki is a tropical hardwood, also known as ‘ironwood’ that is particularly tough and has been used in marine construction for over a hundred years. It is far stronger than Oak. The design of the groynes, as explained below, means that tropical hardwood has to be used and it is essential to ensure that the timber comes from a well‐managed and legal source. By controlling the purchase at the Council, as we have done in letting a separate contract with Wijma UK Ltd, we can do our utmost to ensure the timber meets sustainability and environmental requirements as well as being of high quality.
The structural design of the groynes means that as well as high strength the timber must have the following properties.
Durability
The timber needs to be very durable to withstand the severe marine environment of daily tidal wetting/drying, long exposure to sun, salt water, marine life and occasional impact.
Abrasion
Very high resistance to abrasion is needed as the groyne will be subject to the action of continual movement of shingle against it. During storms the abrasion will be severe.
Marine borers
It is known that both Teredo (shipworm) and Limneria (gribble) are present in our waters. These marine borers can eat their way through all but the hardest of timbers doing considerable damage within five years and limiting the life of groynes to under twenty years. Timber resistant to marine borers is essential.
For coastal defence structures, tropical hardwoods are the only type of timber meeting the three criteria above as well as having suitable strength. There are no other viable alternatives.
The East Kent Engineering Partnership has carried out tests using non‐tropical hardwood in groynes. Douglas Fir lasted about five years in the lower part of the groyne before the timber became riddled with borings and virtually fell apart. Oak lasted about ten years in upper planking in Whitstable before fungal decay turned much of the timber to powder as can be seen in the central photograph below.
On the contrary, we have tropical hardwood groynes more than fifty years old on our seafront which are still serviceable.
The Council has a policy of extensive beach monitoring coupled with a programme of regular beach recycling. This allows us to be very economical with our groyne design because we know the beach will be maintained at a safe level. However it also means that the relatively thin timber members must possess high strength in order to ensure the groyne does not fail.
The type of tropical hardwoods used in groynes (Greenheart, Ekki) has strengths twice that of European hardwoods such as Oak. Lower strength timber can be used but you need bigger pieces to meet the design stresses. This inevitably means you need a bigger quantity of timber and pay more for it.
When you see 515m³ of timber stacked up in the Kingsdown compound it does look to be a vast quantity, but please remember that all timber supply is FSC approved. Our contract specifies that all timber shall be legally sourced and there is chain of custody certification for each piece of timber supplied. FSC (Forest Stewardship Council) is an international, non‐governmental organisation to promote management of the world’s forests and certification is based on 10 principles.
It is widely accepted that tropical deforestation is damaging to the global environment. However, there is a strong case for using timber from a sustainable and well managed source:
- Timber is renewable and is an environmentally responsible option with relatively low energy required for its production;
- When harvested periodically, the forest will be maintained for future generations and there is an economic reason for doing so;
- If not harvested there is the likelihood that the forest will be converted to agriculture, open cast mining or plantation use, which are all damaging to the environment;
- Harvesting gives employment to the local people. Without adequate job security these people will have to seek alternative means to make a living, which usually means “slash and burn” harvesting of the forest which is incredibly damaging to the local environment
- All timber is also milled to finished dimensions in the country of origin. This gives further occupation for the local people and added value to their local economy;
- Managed timber extraction reduces the amount of illegal logging as the market for the illegal timber is reduced;
Our new groynes are designed on the basis that we can re‐use the good quality timber we salvage from the old ones. Old piles will be used as struts to help support the new piles.
Any timber we can’t reuse from the old groynes will be made available to the public or to businesses. We found in the past, where a lot was given away, that some people were taking large amounts and then reselling it themselves. This time, apart from for public projects, we are considering making a small charge for the timber.
Any money made would go to charity. If you do want any timber please remember that:
- The contractor and their workers are here to build sea defences so they might not always have the time to help you straight away
- You will have to organise your own transport to take the stuff away.
- The timber could well have bits of old metal‐work sticking out of it.
- And finally, groyne timber is heavier and harder to work than you think.
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Contact
Liam Wooltorton, Canterbury City Council: Tel: 01227 862454, email liam.wooltorton@canterbury.gov.uk
or
Keith Watson, Dover District Council: Tel: 01304 872399, email keith.watson@dover.gov.uk