Displaying items by tag: Flood Defence
Client: Environment Agency
Jackson completed vital restoration works Parkeston Pumping station in north-east Essex as part of the Asset Refurbishment Programme of Works (APRoW) for the Environment Agency.
UV Lining Installation
In 2018, Jackson refurbished a series of structures conveying the River Ramsey below the railway which runs through Parkeston International Port to the Stour estuary.
The existing failed flap valves in the balancing chamber located on the north side of the railway have been replaced. Three further penstock valves have been replaced with flap valves in the Pumping Station located adjacent to the southern side of the railway. The project also involved the installation of UV lining to repair one of the failed culverts.
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In 2019, Jackson replaced the weedscreen at the lower end of the Ramsey/Dock River which also required piling to both river banks, new steel work and associated Reinforced Concrete pile caps and flood walls.
A new bypass over pumping pipework has been installed to enable dewatering in the event of an emergency if and when required.
The Dock River cannot naturally flow into the Stour estuary, all water, including flood water, must be pumped into the culverts beneath the railway into the tidal estuary. These pumps can hold a maximum of three cubic meters of water a second.
The new weedscreen works will provide a safer more effective means of clearing and maintaining the structure to prevent vegetation from blocking the pumps.
Jackson Site Agent, Lee Dunne said: “This scheme is a culmination of years of hard work and collaboration between Jackson and the Environment Agency under the ARPoW scheme.”
“Now complete, this will improve the functionality of the weed screen ensuring a safer means of maintenance of the pumping station for all Environment Agency operatives.”
“In turn the new emergency bypass pipework guarantees that the Environment Agency are able to dewater the channel in the event of a failure of the main pumps."
Throughout the project, the team worked inside a live port and working closely with port security to minimise disruption to port operations.
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Client: Environment Agency
Jackson Civil Engineering worked with client Environment Agency and suppliers Salix to produce a sustainable and soft engineering solution to strengthen an embankment that was in the early stages of failing at Maylon’s Sluice on the River Crouch, Essex.
The failure was due to the natural erosion of the salt marsh that was protecting the existing embankment.
Jackson and the EA investigated options to reinstate the salt marsh and raise the existing embankment to help prevent future deterioration and lower the risk of flooding. The river is used by local sailing clubs who expressed concern about the embankment’s condition. It had been reported that spectators of the sailing events had been cut by wires protruding from gabion baskets that had corroded and rusted away over the years.
Inter-tidal rivers, such as the River Crouch, are notably difficult to manage when it comes to erosion control, and in our experience, hard engineering is not the best solution in such a dynamic environment. From an engineering perspective, the structure must cope with tidal flux, strong currents and wave action. Biologically, the system must cope with changes in water quality, salinity, seasonal effects and daily exposure and inundation.
The site team, in conjunction with Salix designed a Bioengineering solution using chestnut timber pegs, rock rolls and brushwood faggots that would also encourage future salt marsh growth.
Saltmarshes are highly valued because of the range of ecosystem services that they provide. For example, as they are amongst the most highly productive ecosystems, they support a biodiverse and complex food web that is particularly important to wading and over-wintering birds. In consequence, they are an important component in maintaining biodiversity while efficiently capturing carbon and other pollutants and also providing a high amenity value.
As an alternative to importing clay to site, the site team worked closely with the landowner to obtain planning permission for a borrow pit to be excavated in the field behind the embankment. The borrow pit was shaped and planed with ecologists to provide the best possible habitat for the local wildlife.
As a result, the clay only had to travel approx. 1km by dump truck from where it was dug to where it was placed, instead of being bought to site by tipper lorries which could not be taken directly to the work area, meaning the material would have to be double handled and still transported the last 1-1.5km by dump truck along the farmers haul routes.
In an attempt to avoiding plastic materials, the team installed Eronet, an untreated hessian mat, to hold the topsoil on the embankment long enough for the grass to take hold and prevent further embankment erosion. This was secured with small timber pegs instead of steel pins as the matting is designed to degrade over time. Therefore the pegs will degrade in the same way, rather than leaving an embankment full of steel pins in future.
At the embankment toe, gabion rock rolls were placed to hold brushwood against the embankment. Both are anchored by chestnut stakes.
The system is designed to trap silts in the brushwood bundles and rock rolls. This will result in the reformation of the salt marsh, creating habitat and providing natural protection to the embankment.
This soft engineering solution also had construction benefits: Lighter materials made it easier to manhandle the component parts on the soft muds, and from a sustainability perspective, the materials selected maximised the use of renewable resources, thus lowering the project’s carbon footprint.
During this project, the site team also ran a plastic clean-up initiative which helped to clear three 1-ton aggregate bags of loose plastic debris that had accumulated along the estuary. John Abraham, EA Project Manager said: “I really see this as very positive behaviour from the Jackson team as well as something that should be shared wider within and outside our organisation. If every construction site adopted something like this then maybe we can start to make a difference in the amount of plastic waste within the environment. There is only one thing better than looking at a job well done, but a litter free job well done, regardless of where that litter originated from.”
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.
Work has begun on phase two of the Perry Barr and Witton Flood Risk Management Scheme in Birmingham.
This £14.3m project, funded by the Environment Agency and Birmingham City Council, involves the construction of an additional flood storage area at Forge Mill in Sandwell Valley which lies upstream of Perry Barr and Witton, and will control the passage of flood water downstream.
The flood storage area, which will be the lagest in the UK, has been designed to hold 1.7 million cubic metres of water, protecting 1400 homes and businesses at risk of flooding from the River Tame.
Work is progressing well on the £18m Newhaven flood defence scheme which began in September 2016.
The design for the scheme includes earth embankments, concrete walls and flood gates to provide a one in 200 year standard of protection to over 430 homes and 380 businesses in the area.
The scheme, which spans approximately 3.5km has been split into five phases to minimise the impact of construction work on the town. Parts of the flood defence have also been designed to fit seamlessly into the town’s surroundings. For example, a section of flood wall around the iconic Cormorant statue also serves as a public seating area.
The project is on track to finish in the autumn 2019.
Jackson’s scheme to protect homes in north Birmingham won the award for Top Heritage Project at the ICE West Midlands Awards.
Phase 1 of the Perry Barr & Witton Flood Risk Management Scheme was a £6.5m project along a restricted urban river corridor on the River Tame in central Birmingham. The scheme delivered increased protection to 1,400 residential properties and bought significant environmental enhancements to the river channel.
Part of the Perry Bar & Witton FRMS story shows how collaboration between Jackson, the Environment Agency, local artists and Birmingham City Council looked to make the River Tame safer, as well as reinstating it as a positive focal point for the local community, preserving its rich local heritage. This was achieved by incorporating unique features on the new flood wall along Brookvale Road and establishing a nature trail along the river.
In addition, Brendan Hawthorne, Poet Laureate of Wednesbury wrote a new poem inspiring people to walk, explore and re-engage with the River Tame.
Jackson recently won a design and build contract to construct new flood defences in Newhaven, East Sussex, for the Environment Agency.
This project covers both banks of Newhaven, including the commercial areas near the port, and has a total scheme value of £17m.
The design includes earth embankments, concrete walls and flood gates to protect 431 homes and 387 businesses in the area. The project also includes a temporary flood gate over an existing railway line, and a demountable flood barrier which can be quickly deployed across the highway during a significant flood event.
Construction will begin in November 2016 and is scheduled to finish in 2019.
67% carbon reduction in concrete is a UK first
Jackson Civil Engineering has achieved a 67% reduction in CO2 by using a new type of ‘cem-free’ concrete on a flood defence project in Woodbridge, Suffolk, for the Environment Agency.
This is the first time this concrete has been used in the UK commercially, and the potential for reducing carbon emissions on future construction projects is extensive.
Concrete is a significant contributor to the carbon footprint of the construction industry. The concrete ordinarily used on this type of flood defence project consists of 50% GGBS and 50% Portland cement, which has a typical CO2 value of 158 Kg per m3. In comparison, cem-free concrete is made up of 95% ground-granulated blast-furnace slag (GGBS) and a 5% alkali activator, and has a CO2 value of 52kg per m3.
Although not suitable for all applications, the cem-free concrete was successfully used as an infill in a 265m section of flood wall. This amounted to 51 cubic metres, about 35% of the total concrete used, which achieved a CO2 saving of 5 ½ tonnes. To put this in perspective, it would take five acres of forest one whole year to redress the balance of this carbon output, using the traditional material.
Pro’s and cons
As well as the potential for significant carbon savings, cem-free concrete has better long-term durability, produces less heat in the reaction, making it more suitable for large pours, and requires fewer expansion joints.
There are, however, some minor drawbacks, which make it unsuitable for some applications. For example, during the trials the material did not respond well to floating, which made it unsuitable for use in the floor slab, although with work on the mix design this should be overcome.
The curing time is also slower, which means that shuttering would have to be left for a day or two longer than usual. However, on the right project, with sufficient programming this issue could be overcome.
Jackson’s Project Manager Ashley Tate said: “Over the course of this project, we’ve learned a great deal about the suitability of cem-free concrete going forward. On the right project, and with the correct planning, this material has the potential to generate significant carbon savings for construction.”
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Jackson is currently upgrading nine weirs along the Thames under a design and build contract for the Environment Agency.
The project involves replacing up to 40 weir gates, and installing new head gear, control kiosks and handrailing to five of the weirs. The team has also designed and installed new fish and eel passes on three weirs.
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The Jackson site team recently got more than they bargained for whilst working on a £1.1m scheme to improve the conveyance capacity of the River Soar, just outside Leicester, to reduce the risk of flooding in the area.
The works involve reprofiling and reinstating the river bank, and also constructing new flood embankments at three locations along the river. At one of these sites, on 10th November 2015, the team unearthed some unexploded White Phosphorous Mortars, left over from the Second World War. Jackson General Foreman Dean Hanley explains what happened:
“It was about 3:30pm, and I received a phone call from the guys excavating on the river bank who reported white smoke coming out of the ground where they’d been working. I was at one of the other sites at the time, so I instructed them to evacuate the area and call the police immediately.
When I got to the site, from quite a distance away I could see the smoke coming out of the ground. My background is in the military and I’ve been trained to identify all different sorts of bombs, so I knew what it was straight away.
The police arrived shortly after, and due to my experience, they asked me to speak to Captain Jonnie Barlow from the Nottingham EOD (Explosive Ordnance Disposal) Regiment, who asked me to describe what was happening. He confirmed my suspicions, that it was likely to be a White Phosphorous Mortar, left over from WW2.
Unfortunately, by this time the light was failing, so it was just too risky for the EOD team to do anything that evening. Instead, with the help of the police, we securely cordoned off the whole area, including a number of footpaths, and secured the site for the evening.
The EOD team then arrived at first light, and were able to detonate the remaining mortar safely. They did this by attaching plastic explosives to the device, and then detonating it when all their operatives were safely out of the 50 metre exclusion zone. They also managed to build a bund around the device in order to contain the explosion.”
This is the third UXO that Dean has come across in his construction career, and it’s thanks to his experience and quick thinking that the situation was controlled safely and calmly.
Once the EOD team had disposed of the final mortar, Captain Barlow gave the team the all clear so they could recommence work. He said: “Going forward, Dean should be present whilst the team are working in the area where the UXO was discovered, as I have full confidence he knows the types of ordnance that may be present, and will act accordingly should a similar situation arise.”
History of the White Phosphorous Mortars
In 1940, when the invasion of Britain seemed imminent, the British Government adopted the use of Grenade, No. 76, or Special Incendiary Phosphorus grenade, which consisted of a glass bottle filled with a phosphorous mixture similar to Fenian fire, plus some latex. These were improvised anti-tank weapons, hastily fielded in 1940 when the British were awaiting a German invasion after losing the bulk of their modern armaments in the Dunkirk evacuation. It came in two versions, one with a red cap intended to be thrown by hand, and a slightly stronger bottle with a green cap, intended to be launched from the Northover projector, a crude 2.5-inch black-powder grenade launcher.
During this time, these mortars, along with other munitions, were stashed in strategic locations across the country in preparation for invasion, but were thankfully never required. To this day, unexploded ordnances left over from WW2 continue to be unearthed and dealt with by EOD teams across the country.
What are White Phosphorous Mortars?
On contact with air (when the mortar casing is broken) the phosphorous reacts and creates an explosion. Theoretically, a brand new mortar bomb could be carried around in your pocket quite safely, however, the mortars discovered on the banks of the River Soar had been in the ground for a long time, and their casings had eroded. It only took a small knock from the excavator to crack their cases, which is why one of them went off underground, and the EOD team had to be extremely careful with the remaining device.