Mackley, working as sub-contractor to Balfour Beatty*, has recently completed the Coldharbour Flood Wall Remediation and Foreshore Protection Works on the River Thames on the Isle of Dogs.
The 11-week project is one of several being carried out by the Thames Estuary Asset Management 2100 programme (TEAM2100).
The TEAM2100 programme involves looking after all the flood defence assets along the tidal Thames, from Teddington in Middlesex out to the Kent and Essex coasts. An integrated delivery team consisting of the Environment Agency, **CH2M, Balfour Beatty and selected partners (including Mackley) is tasked with its delivery.
TEAM2100 is responsible for delivering the first 10 years of the Environment Agency’s ground breaking 100-year Thames Estuary 2100 plan.
Site constraints
Due to constrained access from the landside the works were carried out from the river, with materials delivered to the opposite, south bank and a short distance upstream where access is easier. Materials were then transported by a barge to the foreshore as required.
Due to the tidal nature of the site, and with a tidal working window of just two hours, works had to be strictly timetabled to ensure progress was ongoing.
The barge was anchored at the works site each day and supported by a safety boat which was present at all times when work was taking place. When equipment needed to be very close at hand, the barge could be positioned within six inches of the front of the works area.
Good progress
The existing sand bags at the base of the wall have been removed, along with the horizontal timbers and any others that required replacement, and the timber piles on the foreshore were cut off for recycling.
27 new three-metre piles were placed at low tide at a rate of 10 per hour. A small vibration piling hammer was used to reduce noise and disturbance to people living in adjacent properties. With the piles in place, concrete infill was pumped into the space behind the piles, filling the void. The concrete was pumped through the adjacent properties’ gardens and over the wall in a single day.
The foreshore protection works involved the placement of Kyowa rock filter bags at the foot of the river wall.
The Kyowa system is designed to give protection from scour damage to riverbanks, shorelines, bridges and other structures, while at the same time benefitting the surrounding environment. The system comprises mesh net and rocks, and creates the ideal environment for small fish and plants to live in the interspace within it. The system has previously been deployed by Mackley on a scheme of works on the lower reaches of the River Mole in Surrey.
The new timber fenders were then installed, with reclaimed beach groynes used as the material for these.
Brickwork remedial works involved pointing and replacing some bricks. To maintain the aesthetic appeal of the river wall, the team sourced imperial measure bricks of a similar type to the original, from a local reclamation yard. Further works to the downstream adjacent wall are currently taking place.
When the project was complete the site was cleared and any remaining waste removed for recycling.
*Balfour Beatty is a multinational infrastructure group with capabilities in construction services, support services and infrastructure investments.
**CH2M: as of 18 December 2017, CH2M has been acquired by Jacobs creating $15 billion professional services leader providing consultation, design and construction services.
21 February 2018
