Teesworks - Dredging the Tees


The South Tees former steel site is a huge contaminated industrial site which offered considerable potential. If developed properly the site could not only provide long term employment once the most appropriate industries are attracted, but also with imagination as promised in the original 2017 South Tees Regeneration Masterplan also fantastic opportunities for heritage and nature. In fact in predevelopment consultations, the local population stress the importance of nature and heritage not just jobs (2019 South Tees Regeneration Masterplan). Other UK brownfield regeneration schemes (The Avenue Coke Works, Chesterfield) have achieved all three and international examples such as Bilbao have regenerated whole regions(Transformation Bilbao). In Bilbao's case, the regeneration enable progress from a cyclical economy to one that has been stable for three decades so far(The Bilbao Effect).

Teesworks approach does not compare well to best in class nationally and certainly not internationally. For example, the approach to dredging for the Teesworks South Bank Quay development is a very visible demonstration of the lack of ambition being shown by Teesworks, through what appears to be substandard operations, where speed and low cost seem to trump any heritage/environmental considerations. South Bank Quay will create much needed jobs in a sector that really supports the UK's need to move to Net Zero, but the jobs could have been equally created with a protective/precautionary approach to the environment and respect for local heritage. Instead, a short sighted approach where short terms profits both financial and political appear to have been prioritised over real sustainable long term benefits.

I have collated a collection of videos which give some idea of the different dredging operations that have been carried out as part of the Teesworks' South Bank Quay development. For this, I am indebted to all the people who have uploaded their videos to YouTube. I have also used official videos from Teesworks and dredging organisations to show how the dredging operations are portrayed as clean and environmentally friendly. I feel that the YouTube videos show that in fact the dredging has been polluting and undoubtedly environmentally unfriendly.


In order to understand what is happening on and around the Tees, and to be able to make your own mind up about whether the environment is being protected, it is necessary to understand the processes involved. I have done my best to explain some of the background below, if you want you can skip this and just watch the videos first, but please come back to understand why what you see is damaging for the aquatic environment.


Dredging is the process of excavating material from a river bed or the sea bed, examples are the removal of silt in a field stream, digging foundations for a new bridge, keeping a major river shipping channel open or removing sand for building. In the UK dredging of major rivers and estuaries for shipping and new projects normally results in the dredged material being disposed of at sea at designated local disposal sites. Other countries dispose of far less material at sea, instead using it constructively for coastal protection or land reclamation.

The Teesworks dredging is defined as "capital dredging" to differentiate it from "maintenance dredging". PD Ports, the River Tees statutory harbour authority carries out regular maintenance dredging to remove soil that has been washed down the river and sand / sediment that has been washed into the river to keep the shipping channels deep enough for ships to navigate, this is maintenance dredging. The material dredged is then removed to be disposed of at sea, this material is considered part of the river system as it was previously carried by the river.

In the UK dredging results in millions of tonnes of material being disposed of at sea every year at the mouths of a number of major rivers including the Tees, just through regular maintenance dredging.

However, Teesworks has been carrying out capital dredging by removing up to 16m depth of material from the original river bank and river bed, see figure above (MLV2 Options Paper - Final.pdf).

The Marine Management Organisation (MMO) is responsible to ensure the dredging is carried out/specified in a way that is protective to the environment, which it does by issuing licenses after thorough assessment and consideration of the proposed processes. The marine license specifies the way in which the dredging must be carried out and how the dredged material is to be disposed of at sea in order to reduce pollution and protect the environment. However, it is up to the contractor to comply with the specifications, with little checking by the MMO, for example the disposal sites are only checked once every three years for contamination level. The MMO applies the UK laws about river and marine environment and also ensures compliance with the International treaties that govern the world's oceans. In order to create the new South Bank Quay, Teesworks and its sister organisations (STDC/STDL) applied for a marine license (MLA/2020/00506/2) and this involved assessment of the contamination of the area that the material was proposed to be dredged from.

The MMO originally asked the developers to monitor the amount of sediment being released locally into the river at the dredge sites to ensure it did not disrupt the marine ecosystem. This would have involved extra expense and potential disruption to the Teesworks dredging operations, so the developer proposed an alternative that dredging would not take place during July and August as this is when the salmon mainly migrate along the River Tees Estuary. All flora as well as fauna in marine ecosystem can be damaged by exposure to the dredged sediment but only salmon is fully protected in law, I think this is a sign of how the MMO has to capitulate to the demands of developers and so in this case removed the stipulation to monitor the effects on the river during dredging.

The MMO as the regulator has the scope to take a precautionary approach, i.e. not taking chances that a procedure will damage the environment, in the case of Teesworks they did not do this, only applying the minimum which allowed the developers to cut corners. Historical events make it look like the regulatory framework even encourages the developer to cut corners, as is shown in Troubled Waters: The forces behind the death of the Tees.

The entire South Tees site is made ground, i.e. slag (blast furnace waste) which has been used to reclaim the river Tees tidal mud flats and turn them into the steel works. When Teesworks excavated the South Bank site it was able to avoid treating this made ground as waste as UK law does not classify materials that were dumped before 1984 as waste. However, when it was decided the 1km long x 30m wide x 25m depth of river bank that would be removed to make up the South Bank Quay would be disposed of at sea, because the waste is human made under the London Convention (Wikipedia) it is not allowed to be dumped at sea. So the top 8m of made ground (blast furnace waste/slag) was excavated to land.

Contamination is a whole other story...

South Bank Quay Marine License Application(Edit)

The construction of the South Bank Quay is covered by a number of planning applications and 2 marine license applications. This animation from Teesworks shows a very sanitised version of what was supposed to happen:

At 1 minute 9 seconds the animation shows a clean waterside dredging operation with no mention of material spilling into the Tees or any mitigation to stop this happening. Ok, this is only an animation but this is probably the only thing people saw who didn't read the 1000s of pages of the different applications, so it should show both the drawbacks as well as the benefits of the the quay construction. As it stands, people are not being shown the whole picture and are not aware of the risks.

One of the marine license applications, South Bank Quay Phase 1 MLA/2020/00506 plus variations 1 and 2, includes thousands of pages related to the South Bank site including much information related to its industrial history. The site has been used for over 100 years for a wide variety of industrial uses, the major ones being related to iron/steel making, in fact the area was classified at the most dangerous hazard level (COMAH) due to the by-products of coke making that remained on the site at the time of the application. The major by-product, coal tar is a dangerous mixture of chemicals distilled from coal whilst being transformed into coke. The COMAH status was due to the 1000's of tonnes of mainly coal tar related material still on the site, what is unknown is how many thousands of tonnes of material have leaked into the site over the 100 plus years of coke oven operation. The license application also contains the chemical analysis for the suite of chemicals that is specified by OSPAR (Oslo and Paris Convention) as having to be tested if material is to be dumped at sea (OSPAR dredging and dumping). Samples that had been taken of the river bed and the river bank all had high level of polycyclic aromatic hydrocarbons (PAHs), which was not surprising bearing in mind the site history of coke production. As there is no explicit requirement in OSPAR regulations for a developer to test for other coal tar / coke related chemicals these were not detected as they were not actually looked for.

However, even with the limited range of chemicals tested for, about a third of the river bed that was to be dredged for the berth at the South Bank Quay was so contaminated that it was classified as an exclusion zone. So the material that was dredged from this exclusion zone was excluded from being disposed of at sea and instead had to be brought to land for appropriate disposal or cleaning.

It is also worth noting that all the material that was allowed to be disposed of at sea will have been contaminated to some extent, we know this both from the record of historical industrial activity and waste disposal into the Tees and from the limited sampling carried out before the dredging occurred. The disposal at sea is allowed because it does not breach current internationally agreed limits and because there is an assumption that development takes precedence over potential environmental damage. The MMO had to make a subjective judgement on whether the cumulative effects of dredging will cause sufficient damage to warrant blocking of disposal at sea. The MMO takes advice from CEFAS, who stated that while levels of contamination were high enough that disposal at sea should not be allowed, due to previous activities in the vicinity of the Tees, disposal at sea should not be precluded (18th June 2021 - CEFAS Follow up Advice MLA/2020/00506&00507). So, in the case of the sea around the River Tees due to its history of pollution, adding more contamination is acceptable. In other words, in other marine areas without an industrial past, it could be assumed that the disposal would not have been acceptable and the environment would be protected. I think this approach can only be detrimental to the Tees environment as contamination is cumulative, the more contamination is present the more chance of environmental disaster, so in fact a precautionary approach would be to set tighter limits for the Tees rather than loosen the limits as has been done for the South Bank Quay.

Teesside South Bank Dredging 11th October 2022(Edit)

In fact the material from the exclusion zone was so contaminated that the developers were required to use a closed bucket dredge as the license application state this would produce virtually no uncontrolled release of material into the river at the site of dredging, to quote, "An enclosed grab results in virtually no release of sediment as the material is dredged" - South Bank Quay - Supplementary environmental information report.

Sadly the closed bucket used, wasn't closed as is visible in the October 2022 video (as reported by North East Bylines) and now measured by the contractor as reported in one of the Marine License Application return documents MLA/2020/00506 Condition 5.2.11 - P03, so much contamination was spread from the excluded dredge site, this resulted in the requirement to carry out very localised remedial dredging to remove the contaminated sediment around the excluded area, but as the planning documents show locally released sediment will have been deposited over most of the River Tees estuary. However, Teesworks only remediated close to the exclusion zone meaning that excluded contaminated sediment will also have been dumped at sea either through the cutter suction dredger Athena's capital dredging of the rest of the berthing pocket adjacent to the exclusion zone or by PD Ports maintenance dredging of the main channel adjacent to the exclusion zone.

Further analysis of the post dredging contamination spread is shown in Teesworks - Recorded Contamination of Tees by Closed Bucket Dredging.

The video below shows the reality of dredging from the exclusion zone, a digger with a bucket with a lid on a boat digs into the river bed, brings up material and deposits it onto a barge. Then you can see two excavators on land unloading the barge into tipper trucks. The whole operation seems to have required great speed as material is seen dropping out of the buckets at all stages and little indication of care being taken to protect the aquatic environment.

While remedial dredging to clean up the material spilt by the closed bucket dredge did reduce the level of contamination of the river bed, the river bed was still left considerably more contaminated than before the dredging was carried out. Isn't the dredging supposed to at least not make the river environment more hostile to aquatic species?

Once again we only know about the areas tested and we only know about them when there were tested. So we don't know how much higher the contamination levels were immediately after the exclusion zone dredging or how wide the spread of contamination is over the rest of the River Tees Estuary and even out to sea.

Dinopotes Dredger 5th Feb 2023 River Tees/Freeport(Edit)

Dinoptes is basically a boat with a digger on its back and much like any digger it makes a mess. This can be seen very clearly in these videos with contaminated sediment being stirred into the river by the digging operation and being dropped from the bucket during recovery to the boat. It is believed that the remedial operations to clean up after the previous nominally closed bucket dredging would have looked much like this, as we believe Dinoptes was the only dredger of this type available to carry out the work.

This stirring up of sediment into the river by a single dredger is going to considerably increase the load the river is carrying and will spread any contamination which exists from current and historical pollution of the River Tees. In fact 2 dredgers were operating in the area of South Bank as you can see at the end of this video, so even more sediment.

Athena South Bank Quay 5th February 2023(Edit)

Athena is a cutter suction dredger, basically a huge underwater rooter that breaks up the river bed, the dredging head is surrounded by a suction tube, which sucks between 80-90% of the material removed from the river bed and transfers it to an attendant barge. The barge when full is then taken out to sea where the material is dumped, leaving between 10-20% of the dredged contaminated material behind suspended in the river.

The Athena is the sister dredger to the Artemis, whose features and operation are shown in this video. The way a cutter suction dredger operates is explained via an animation, note that in the animation the suction appears to remove all of material that the cutter has loosened, in reality when correctly operated only 80-90% is captured.

This video shows a comparison between the Athena, cutter suction dredger, and the Dinoptes, excavator dredger. The Athena is ready to start dredging to deepen the turning circle within the main river away from the quay.

South Bank Quay 12th February 2023.(Edit)

The dredging of the River Tees is part of the wider South Bank, this video gives a good view of the 1km South Bank Quay edge which was built inland, with the 30m x 1km x 25m of river bank being removed after construction. You can see the remaining river bank left in the river awaiting excavation at the eastern end of the quay, with the Athena preparing to dredge at the western end of the quay.

Athena Feb 16th 2023 part 1(Edit)

While the operation of the Athena is not visible in this first video, it gives a good view of the process. The Athena is connected by a floating pipe to a barge. The dredged material carried in a lot of water which has been sucked up is conveyed down the pipe into the barge. When the barge is full, it disconnects the pipe and the barge proceeds to the disposal site, in this case Tees Bay C, about 6 miles off shore.

In this video it can be clearly seen how the dredging operation is stirring up the river sediment. It also looks like dredging was still continuing when the barge was disconnected. This could be a procedure carried out to speed up dredging, pre-cutting is a procedure where the cutter operates but discharges the material back into the river just behind the cutter head. Then when the barge is reconnected the head is able to move rapidly to suck up the already cut material. Pre-cutting will result in greater loss of sediment into the river at the dredging site.

The contamination of the river Tees sediment means that the more the sediment is stirred up, the more contamination will be spread into the river, across the river bed and into the sea. So if pre-cutting was taking place then additional unnecessary contamination would have been spreading into the river, which could have been avoided by not carrying out pre-cutting.

Athena Feb 16th 2023 part 2(Edit)

Further video of the Athena disconnected, once again appearing by its rotation to be continuing to cut.

Teesworks South Bank Quay 30th March 2023-14th April 2023(Edit)

The resuspension of riverbed sediment is all too clear, with material of all sizes changing the rivers colour around the Athena and presumably mainly fine sediment being allowed over the weir on the barge as the suction dredged sediment settles in the barge effectively dewatering the sediment in the barge. The more water that is allowed to leave the dredged material in the barge, the larger the loads of dredged material that can be removed per trip to the disposal site, but the greater the amount of dredged material which is released back into the river.

The video starts with images of the large bunded mound which is believed to be the material dredged from the exclusion zone. This material is so contaminated that it can not be disposed at sea, it has been piled near to the river to dewater with the required bund to capture any water which is stated in the marine license will be treated before disposal.

The two excavator dredgers are working towards the western end of the quay, with the Athena operating towards the eastern end of the quay.

The material dredged by the Athena is allowed to be dumped at sea, so you can see the hopper barge connected by the floating pipe. The water around the hopper barge shows the material which is being released from the barge as the dredged material is allowed to drain into the Tees. The more water that can be removed from the material piped from the Athena, the fewer times the hopper barge has to taken out to the disposal sites.

Finally the Athena cutter suction dredger can be seen in operation and unlike the animation the amount of sediment which is not caught by the suction can be seen by the change in water colour around the cutter head, travelling to the stern of the boat.

South Bank Quay 28th May 2023.(Edit)

This shows crude dredging removing what was previously the river bank. An excavator on a barge is being used to dig away the river bank that has been left in front of the quay. This is really excavation rather than dredging as this is river bank, not river bed, however a variation to the original license (MLA/2020/00506 variation 2) was granted for the river bank to be disposed of at sea as well.

The View from Space(Edit)

The EOS Sentinel Hub allows you to see images of the earth from space collected by a number of different satellites, for example the Tees Estuary.

The river Tees is one of the most sediment laden rivers in the UK. The sediment is the result of poor land management up stream from the Tees barrage, mainly run-off of soil from bare fields and of peat washed off the moors due to over grazing. So by the time the Tees reaches the barrage it is impossible to see the river bed, this hides any further pollution when it enters the river downstream from the barrage.

When there is heavy rain you can see the peat being carried out of the Tees estuary from space, as was the case on 27th October 2019 (click image for hi-res):

However, on 4th April 2023 when the Athena was dredging, the amount of disturbance being caused from the dredging operations is so considerable that the change in the colour of the river is also visible from space (click image for hi-res):

The satellite image can only show a colour change, but it gives a visual record of how far material escaping from the Athena cutter suction dredging was being carried out to sea with the river flow and we know that the Athena was dredging contaminated sediment.


The planning and license applications give the impression that the dredging of the Tees being carried out to build the South Bank Quay is a clean and therefore safe process. However, the precautionary principle has been ignored, partly as the documents show, with every opportunity taken to minimise risk and present a picture of clean processes.

Thanks to the efforts of all the people who have documented the operations for us, we can see that capital dredging of the River Tees for the South Bank Quay is anything but clean.

It matters that the processes are not clean as all the dirt that can be seen spreading throughout the river Tees carries contamination from decades of industrial waste that has ended up in the river Tees and within the land upon which the industry sat.

The safe remediation (clean up) of the Teesworks site should be carried out carefully due to the high levels of contamination to avoid damaging the environment and creating a potential risk to all life. It appears that in order to save money and meet arbitrary political timelines the river works are anything but clean and safe. The construction of a cofferdam around the South Bank Quay berthing pocket would have been one way to avoid further contamination of the river, but would have cost more and taken longer. Equally finding beneficial uses for the dredged material would have avoided contamination being dumped at sea, once again this would have taken longer, but it may not have been more expensive.

The recovery of the Tees its estuary and the surrounding seas has been a slow many decade process as industry stopped using the Tees as its sewer. The unnecessary contamination caused by the Teesworks dredging has set this process back, such that the recovery of the local environment now will take even longer and the environment may never be the same again.

N.B. Teesworks capital dredging did not start until after the complete die-off of inshore crabs around the Tees Estuary in 2021, so Teesworks' capital dredging was not the cause of that die-off. However, many subsequent marine wash-up events have happened on our local coast (Chronology of Marine Die-offs) and it appears die-offs are still occurring since the Teesworks' capital dredging started.