0 In Farm/ General

Thog tuinn an cinn – Wave Action!

Thog tuinn an cinnwaves reared their heads!

I have said this before but it is definitely worth repeating, the sea is a good servant but a terrible master. You can never take the sea for granted and if you do only trouble shall follow.

So what am I talking about? Well we had the first autumn storm recently and by the standards of this part of the world it was not exactly spectacular, although unusually the wind direction kept changing and was churning up the sea. As a result, there was quite a bit of wave action and our new aquaculture equipment took a battering and unfortunately we suffered quite a bit of damage.

If brief wave action and swell pulled the posts that make up the systems out of the seabed. It seems that what happened is that one or several of the posts on one line came free, this then led to further stress and a ripple affect caused all posts in a 50m section to lift out. These posts either then broke free and drifted off or started to wind themselves around the neighbouring line causing this to come under pressure as well, with the upshot that posts were pulled from this line as well. All in all we have lost at least half of each of our two systems and a good few baskets as well.

Going out on site that day was heartbreaking because so much time, effort, hard work and sweat has gone into the project this year. So the first order of business was to move all the baskets onto the remaining structure which was just big enough to house them all; we managed to find most of the baskets that had broken free close by on the shore and thankfully all the stock was still alive. The next day we were back to do emergency repairs and we nailed batons across all of the pairs of remaining posts so that it would make it harder for the sea to pull them out.

The following weekend we went back to check everything out and despite there being a neap tide and being unable to see the actual structures, there was no evidence of any further damage i.e. posts floating on the surface still attached to the line. We then spent a few hours combing the head of the loch looking for lost posts and baskets and managed to find six baskets and twenty eight posts. The good news was that the oysters in the baskets were all still alive, the bad news was that it was back breaking work having to carry twenty eight 1.8m posts back to the van.

Back at base it was time for an evaluation into what had gone wrong. We did not have any issue with the posts of the trial system and the only difference between those posts and the new ones is the post length, the trial posts were 2200mm and the new posts are 1800mm. So it looks like the crucial difference here is 400mm of length and at our site this could be important because in this 400mm is a layer of gravel that could be crucial in bedding in the posts.

Unfortunately for us we purchased a significant supply of these shorter posts so we need to find a way of reusing them and so we have made a number of design changes:

  • On each line of posts we are going to introduce longer intermediate posts. These posts shall be 2400mm in length and placed 1 for every 4 or 5 of the smaller posts. This shall add strength to the system and break it down into smaller units so minimising the impact of any smaller post lifting out.
  • Each of the posts shall have wedges attached near the point to make them resist an upward pull; this is a solution employed in Australia and Japan, and has been successful in solving this issue in those countries.
  • Each pair of posts shall have a baton nailed across the bottom; this shall make it harder to disrupt the integrity of the system as two posts shall be required to be pulled out instead of one.

And so the rebuild started in late October and by this week we have now completely replaced 7 lines of posts with the new design. That still leaves us one line short of having two complete BST systems.

However the obvious question and acid test is would this solution actually work? We needed to wait for bad weather and we did not have long to wait. Just a couple of weeks after we had started replacing the posts a wee storm rolled in off the Atlantic to provide a test. A couple of days of steady 40mph winds, gusting up to 55mph and turn west to north westerly. Observing the scene we have now learned that despite being a relatively sheltered glacial fjord if the wind turns to the north west it pours down the loch and creates significant swell, unusual and not what you might expect, although it does tie up with reports from the old days when many a mariner was disappointed not to find safe shelter in the loch. Anyway the new design managed to survive the battering with no issues which as a relief.

Roll on December and next up was Storm Caroline. Now, this was a biggie, so big they even gave it a name. This storm delivered high winds of up to 70mph, crucially for us blowing in from the north west and at a time of big spring tides, the worst possible combination or best, depending upon your point of view!

When we arrived back on site after the storm, it was a rather nervous time waiting for the tide to go out and we were all concerned about the fate of the new posts. This was not helped by the fact that the sea had damaged the pier (again!), ripping up several large blocks from the slipway; it definitely did not inspire confidence that the lines were going to be fine.

We waited and waited, watching to see the systems appear – it was like waiting for the world’s biggest kettle and you know what they say about a watched kettle. After the first anchor posts emerged, I could just not wait and had to wade out for a closer inspection.

It was tough going wading out as it 500m+ from the shore, the water is above waist height and there was a swell too, did I mention that is was also freezing cold, raining and windy? Still we got out there and thankfully everything was fine. The posts were all solid and doing what they are supposed to be doing – what a relief I can tell you! And so the new design is doing well and we now have a bit of confidence that this solution is going to do the business for us.

Of course, we are now a bit behind schedule in regard to building the lines, but we are ahead of schedule in terms of what we have learned this year and that shall pay back next year. So all in all not a bad way to end the first full year.

Nollaig Chridheil agus Bliadhna Mhath Ùr dhuibh uile.

You Might Also Like

No Comments

Leave a Reply