Hi, Glyn Onione the Senior Technical Consultant for Aquatic Engineering in the UK here again to answer another great question we are often asked. Which is – Silt Curtains – Do They Really Work?
You only need to type the question into your favourite search engine, such as Google, Bing or Yahoo – ‘Silt Curtains do they work’ and you will be inundated with responses, whether personal, professional or academic! You can even watch a video – “I hate silt curtains” on their Face Book page!
Our cutting edge and environmentally conscious company on the Isle of Wight designs, fabricates and installs silt curtains around the world, so I’m a little biased! However if we disregard that simple fact and I go on my own experience, we fabricate around 10km of curtains a year, then the answer is simply Yes, Yes and Yes again, they work and I would go as far as to say their effects can be nothing short of amazing! However, that doesn’t mean that if you buy an “off the shelf” silt curtain or turbidity curtain and throw it into a lake that it will work as you want it to! Far from it!
I often use the analogy of cars: If you wanted to enter the Dakar Rally then a Formula One car of any type would likely serve you badly and cost you dearly – conversely, you would be poorly served driving the close on, a 2.5 tonnes fully laden, Mini All4 Racing around the Monaco Grand Prix circuit. It is horses for courses in just about every aspect of our lives, so why should silt curtains be any different? A heavy duty Silt Barrier may last you 5 years, but why would you want it to if your dredging contract only lasted for 2 weeks! Or if you were installing sheet piles along the tidal Thames for several months is it unlikely that a thin cheap product would be up to the abrasive rigours of tidal mudflats full of the junk of humanity?
I’m often told, well we can reuse it on the next project! But is it likely that your next project will be the same length and depth, as well as the same conditions as the one before? We here at Aquatic Engineering can go a year or more without selling two identical Silt Screens aka Floating Silt Curtains.
It is always preferable to design the best value product of the right dimensions to “keep silt in its place” for our clients. Yes we do have some silt curtains made up on the shelf, however these are not held as stock items, rather they are cancelled orders or second user systems that we have acquired over the past years of trading, occasionally we can offer them to our clients at a knock down price, but not very often, because invariably they are not right for the job!
So why do Silt Curtains come in for so much bad press – the answer is simple: the customer was sold a Mini All4 to drive the Monaco Grand Prix! Secondly another reason Silt Barriers of any type fail are when they are poorly installed – just do a simple search on Google Images and you will see a whole range of poorly installed Silt Curtains, you can see the curtain lifting from the bed of the lake and silt billowing underneath because of the water pressure. Poor anchorage is a subject I will deal with another time, but suffice to say, good Silt Curtain Anchorage is paramount to their successful installation. This is simply so that they actually do what they designed for.
However, Turbidity Curtains can fail to “keep silt in its place” for a whole range of reasons. For instance, the currents are too strong; the curtain doesn’t reach the bed of the water body so there is no seal; they were poorly constructed; they were poorly installed; boat traffic or contractors machinery have damaged them – or simply it is the wrong curtain in the wrong location!
That is why we pride ourselves at AE in designing an appropriate Silt Containment System for our clients, no matter where they are or what their budget is, getting it fabricated the same day and if required with them onsite within 24hrs.
Remember the more questions you ask, or are asked, the more likely you will get a Silt Curtain System which will “keep silt in its place”. That’s where our many years of expertise can assist in all types of projects – Working Above Water, On Water & Under Water, we are Aquatic Engineering!
But what are Silt Curtains made of and how are they made? Well that’s an interesting question and I hope to answer that in a future post, along with many more of the questions you email me. Please keep them coming!
If you have any questions or would like to talk through your civil engineering projects please get in touch.
Glyn Onione, Senior Technical Consultant at Aquatic Engineering
Call 01983 616668 Keep up to date with our silt curtain installations here