Client: Environment Agency
Originally built in 1970’s, the 15 kilometres of existing flood defences offered a low standard of protection against a flood event, with a 5% (1 in 20) chance of flooding in any given year. Now complete, the upgraded flood defence increases the standard of flood protection to 0.33% (greater than 1 in 200). This scheme improves the protection to 1,608 households and 422 commercial properties.
Replace Flood gates to lock – £1.2m Value - 2008
This phase included replacing the existing gates at Neptune Marina to increase the level of flood protection. Jackson then undertook extensive works to strengthen and raise the quoins which involved chemical grouting to improve the substrata and ground anchors with reinforced concrete. All works were carried out within the operational port. The gates were fabricated in Holland and transferred across the North Sea on a barge. These were then lifted into position with a 250 ton mobile crane.
Jackson excavated 7 trial holes of 2.5 metres deep and 15 metres long to locate services along the east bank. This led to numerous service diversions to position them within a service corridor to facilitate the construction of the proposed flood defence works.
East & West Bank Flood Defence - £4m Value – November 2009 to March 2011
The works at East Bank consisted of installing a 350 metre brick clad sheet pile flood defence. To construct this defence, Jackson mainly installed sheet piles using a leader rig as well as a short section of secant piling adjacent to a UKPN substation.
These works ran from high ground at ECO Oil’s depot, across the access road pass Red 7’s Yard stopping short of the lock due to existing 132KV cables. Due to the presence of the outfall to the Ipswich storm drain the sheet piling was staggered/overlapped and the gap filled with the port road ramp built on expanded polystyrene.
West Bank works faced many challenges during construction due to the adjacent railway. Jackson installed a further 340 metre of sheet pile which was faced with brick work from Bath Street at the Northern end to the Riverside Industrial Park.
Where the railway embankment rises to cross Wherstead Road, sheet piles were driven to the required flood defence height and again faced with bricks and in-filled with concrete. These continued until the embankment achieved the flood defence level and the sheet piles returned in to the embankment.
In front of Persimmon Homes, sheet piles were driven to form the seepage cut-off and reinforced concrete cap cast to provide a connection for precast concrete wall panels to be grouted into and later faced with brickwork to match the east bank work.Wherstead Road/West Bank Terminal and Constantine Weir - £2.2m Value – 2011 to 2012
On the West Bank Terminal, the flood defence is created by a ridge in the block paving. A 15,000m2 area of concrete block paving was lifted and disposed off site. The area was then raised by 300mm with lean mix concrete before being re-laid with new concrete block paving.
This was carried out progressively across the container park keeping areas operational as work progressed.
At the rear of the properties on Wherstead Road, a small embankment was built from stony cohesive material a clay core to keep the slopes as steep as possible and to fit in a narrow strip of land.
On the left bank at Constantine Weir, approximately 30 metres of the sheet piles situated at the weir and control structure had begun to fail. This stretch of sheet piles also verged on the river bank by a Site of Special Scientific Interest. In addition, a pair of 135 kV cables that were sensitive to vibration ran close to the wall.
As a consequence of these factors, the piling had to be installed using a Silent press and due to the restricted access, this was all serviced by a 100t hydraulic crawler crane positioned on concrete strip footings that were founded below the cables.
On completion of the piling the control structure was reconstructed within the tidal zone inside a Portadam for protection.