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Is there more than one type of cofferdam?

You could say that yes. There are number of different varieties of cofferdam for a range of different purposes and we look of those now in detail.

Already know your cofferdam from your vibration hammer? Give one of our friendly, expert team a call on 01257 696041 for advice and guidance on your project’s excavation strategy.

The cofferdams that exist fall into a number of distinct categories, dependent on the depth of excavation required, the condition of the soil, type of material used in its construction and whether there are any fluctuations in the level of water.

The available types of cofferdam are explained below:

The Rockfill Cofferdam is permeable and is used for the enclosure of a site that is about to be drained of water. The piles themselves allow water through them, but seepage is prevented by an impervious membrane and they also feature what’s known as a ‘rip rap’ that protects the interior against any wave action.

The Earthen Cofferdam is used when the depth of the water in question is relatively shallow (under 3 metres) and the speed of the current in the area is minimal. As its name would suggest, the earthen cofferdam is created using materials available in the local area, such as fine sand, soil or clay.

The top of this kind of structure is typically set at around 1 metre above the highest possible level of water, which ensures that even when the waves get bigger, they don’t enter inside. As this type of cofferdam features sloped edges, they are usually covered with stones and rubble to ensure that the movement of the water doesn’t affect the embankment and once the construction phase is ready to commence, the water on the inside of the structure is pumped out to allow work to occur beneath the water line.

The Single Walled Cofferdam is most suitable when the depth of the water on site is in excess of 6 metres and the construction site itself is relatively small. Most often employed in bridge construction, it is created by driving sheets of timber into the bed of the river, covering the perimeter of the site area. Inside this area, heavy iron or steel sheets are held in place at the correct distance apart by metal struts known as ‘wales’.

Again, like other types of cofferdam, when required, water is pumped out, allowing the required works to begin.

The Double Walled Cofferdam is similar to its single walled counterpart, as it is used when the water depth measures 6 metres or more, but it is different in respect of the fact that it is used on larger construction sites. If a single walled structure were to be used in this kind of scenario, it would need extensive supports, making it economically unviable.

The extra stability that this configuration of structure offers, means it is able to hold back water of a depth of up to 12 metres.

When the piles are driven into place, a gap is left between each one and they are bolted together and the deeper the water, the bigger the gap that is required. This gap is not left empty, rather it is filled with soil to a) lend the cofferdam even more strength and b) prevent any leakage from the ground below.

This type of cofferdam requires the piles to be driven significantly further into the river or sea  bed.

The Braced Cofferdam is an option used when difficulty is encountered when driving the piles into the bed of the water. It is created by using two separate piles, supported laterally with wooden ‘cribs’, forming pockets, which are filled using earth and stones.

The frame of the structure is typically made from wooden logs and is put together on dry land, before being floated out to where it is to be constructed. Preparation is key with this type of project, as all the loose soil and other materials covering the hard bed must be dredged away.

Once drained of water, the cofferdam’s structure is filled with concrete and once it has set, the overlying structure is taken away.

The Cellular Cofferdam is reserved for when the project in question is required in waters exceeding 20 metres. This is a serious structure that is usually only employed by large-scale construction firms or when a lock, weir or dam is being created.

To form this kind of cofferdam, straight steel piles are driven into the bed that interconnect with each other and are pre constructed to meet project parameters. Once installed, they are filled with either gravel or sand to add stability.

Call 01257 696041 now for advice from our expert team on which cofferdam structure best suits your project requirements.

Of course, the cost is relative to the particular job in hand, but our team is dedicated to finding the most cost-effective solutions to our clients’ needs without cutting corners or jeopardising the safety of anyone on site.

Why work with us?

At Stuart Piling, we have more than 30 years of experience in all aspects of the sheet pile industry and the use of cofferdams. That includes decades of know-how in:

• Sheet pile installation
• The installation of bracing frames to cofferdam design
• The extraction of sheet piles and bracing frames
• The installation of concrete working bases

Not only that, but we are very much focussed on the environmental impact of the work we do and are quick to adopt and closely adhere to all the latest regulations and directives in the industry. This means that when you employ us, you can rest assured that you’re working with an ethical company that cares about its effect on the local surroundings.

If you would like to learn more about cofferdams and how these useful structures could be used to benefit your project or if you would like some guidance on any other related construction matters, please call us any time on 01257 696041 for some friendly, no obligation advice.

We look forward to talking with you and making your construction plans reality.