Filter Units Civil Engineering Applications

Kyowa Filter Unit are protection units suitable for installation on river banks where stabilisation or protection is required. They can be successfully installed on uneven, sloping surfaces and integrate perfectly in challenging topographic watercourse environments.

Kyowa Filter Units or rock bags can be used for temporary measures where a collapse has occurred or is imminent, or for longer term civil engineering projects. There have been over 17,000 civil applications with filter unit in its home country of Japan with no failures.

Please feel free to contact a member of our sales team on +44 (0) 2890 454599 or click the button below to send your enquiry via email.


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  • Fast Installation
  • Single point lifting system
  • Significantly reduces vessel time
  • No riverbed preparation required
  • Develops marine life
  • Environmentally friendly
  • Accumulates sediments
  • Flexible & durable
  • Rapid preparation
  • Lifetime minimum 50 yrs in saline water
  • Lifetime minimum 30 yrs against UV rays
  • (Also known as rock bags)
Kyowa Filter Units, rock bags
Filter units or rock bags in place on river bank.

Bridge pile scour protection

River embankment stabilisation

Emergency counter measures against flooding

Port and harbour scour defences

Coastal zone stabilisation

Subsea dykes and groynes

Click for image of Kyowa Filter Units Protecting Historic London SiteKyowa filter units protect historic London site

In February this year emergency works were performed on the Tower of London foreshore to prevent further undermining of the wall adjacent to Tower Bridge.   Mackleys Civil Engineering was awarded the contract by the Environment Agency to install over 200 2 tonne Kyowa filter units as a method of scour protection at the historic site.

Designed by experienced consulting engineers Arup, the filter unit solution was selected as it provided options for possible additional works at the site.  As work has not been completed at the site there’s a possibility that the filter units will need to be removed after a short period of time.  This was one of the significant advantages of utilising the filter unit system as its one point lifting ring which remains attached to each bag making  the retrieval process simple and cost effective.

Click for image of Filter Units installation.The versatility of the filter unit provided Mackleys with options; either install by barge or use a long reach machine located in the pedestrian area at the top of the wall.  As the site attracts thousands of tourists every year it was important that the site was not congested with heavy equipment and access for pedestrians to the historic sites was still made possible.  Mackleys after conducting rigorous health and safety checks established that installation could be achieved using a 360® forklift located at the top of the wall lowering the bags into place on the foreshore.

Before the bags were installed Ridgeway and Sumisho-Kyowa Ltd were given the opportunity to present the product to the design engineers at Arup which ultimately resulted in the product being specified for the project.  Ridgeway supplied the bags to Mackleys Civil Engineering and demonstrated the filling method to the engineering team.  Mackleys filled the bags at a quarry located in Kent and transported to site via road, offloading and stock piling in small quantities on site prior to installation on the foreshore.

Installation work by Mackley Construction – Contact: David Knapp: