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===== Even "Safe" Dredging Caused Increased Contamination =====
**Teesworks dredging has polluted the Tees riverbed.**
==== How do we know this? ====
Teesworks have measured and reported the state of the river before and after dredging. These results should be judged by Mayor Houchen's promise in September 2022 [[https://www.dredgingtoday.com/2022/09/29/teesworks-and-graham-kick-off-dredging-of-the-river-tees/|Dredging News]], "Let me be clear, not a single gram of dredged material will be disposed of in the river or out to sea. Everything is being removed from the river and disposed of on land."
These tables show that what should have been a reduction in contamination is actually an increase. All the red boxes are where after the remedial work was carried out to overcome the contamination caused by the dredging the contamination is more than that which existed prior to dredging. All the boxes should have been green, showing that the dredging had removed contamination.
The data here is only for the 4 locations which were checked for contamination both before dredging and after remediation, each row has measurements for one location, and each column is for a different chemical (full table is further down). We don't know how much contamination spread to the wider river as no measurements have been made.
|Metals|Arsenic (As)|Cadmium (Cd)|Chromium (Cr)|Copper (Cu)|Mercury (Hg)|Nickel (Ni)|Lead (Pb)|Zinc (Zn)|
|SS03|-2|-26|-31|-37|-38|-6|-13|-24|
|SS04|1|-64|-34|-25|-27|-28|-37|-40|
|SS05|11|-36|-31|-29|-28|-24|-27|-24|
|SS06|-4|-33|-24|-21|-23|-18|-15|-10|
|OrganCl|AHCH|BHCH|GHCH|DIELDRIN|HCB|PPTDE|PPDDE|PPDDT|
|SS03|90|64|81|45|-789|-63|-833|-233|
|SS04|76|61|75|61|-756|15|-507|52|
|SS05|83|50|71|35|-739|-30|-587|43|
|SS06|72|39|72|40|-1056|-16|-660|-200|
Green is good - less contamination after the work had been completed, but red is bad - more contamination after the work had been completed.
All the cells should be green, they aren't so the river has been damaged by the dredging.
===== Background =====
The River Tees is known to be a highly contaminated river due to largely to the historic industries which have occupied its bank and environs. So any deep dredging should be undertaken with suitable care.
In fact one area of the proposed area to be dredged was so contaminated that the material had to be disposed of to land and not allowed to spread into the river. The red rectangle shows the exclusion area.
{{url>https://umap.openstreetmap.fr/en/map/south-bank-quay-marine-works_858022?scaleControl=false&miniMap=false&scrollWheelZoom=false&zoomControl=true&allowEdit=false&moreControl=true&searchControl=null&tilelayersControl=null&embedControl=null&datalayersControl=true&onLoadPanel=undefined&captionBar=false}}
[[https://umap.openstreetmap.fr/en/map/south-bank-quay-marine-works_858022|See full screen]]
===== The "Clean" Dredging Proposal =====
The construction of the South Bank Quay required the deep dredging of river bed, which included removal of 30m x 1km x 16m of river bank (MLA/2020/00506{footnote}See full application for details [[MLA-2020-00506|Marine License Application MLA/2020/00506 plus variations 1 and 2]]{/footnote}). Before dredging could be undertaken sampling of the area to be dredged was carried out and one specific area around borehole 34 (BH-34) was so contaminated that the Marine Management Organisation (MMO) specified that the material could not be disposed of into the sea 6 miles off the Tees estuary. Additionally because the material was so contaminated that the dredging had carried out in such a way as to eliminate any chance of contamination spreading into the river at the dredge site. STDC's / Teesworks on advice of consultants Royal Haskoning DHV stated that containment of contamination would be achieved by "An enclosed grab results in virtually no release of sediment as the material is dredged.{footnote}[[this>Teesworks/Planning/MLA_2020_00506/MLA_2020_00506-PC1084-RHD-ZZ-XX-RP-Z-1115_South Bank Quay supplementary report-16.pdf|South Bank Quay - Supplementary environmental information report]]{/footnote}
===== The Contamination Caused by Dredging =====
So it is damming that any contamination of the river bed around the dredge site occurred during dredging and the river bed has been left more contaminated after dredging than before.
We know that the dredging caused considerable contamination of the river bed around the exclusion zone dredge, only because one of the conditions of the marine license was that sampling had to be carried out after the dredging. The sampling showed that the enclosed bucket dredging had caused increases in contamination all around the exclusion zone, or at least at the only 6 locations sampled.
{{this>Teesworks/Planning/MLA_2020_00506/images/MLA_2020_00506-PC1084-RHD-SB-EN-ME-EV-1145-Condition 5.2.11 Note P03-02.jpg}}
The figure shows the six locations at which surface scrapes were carried out to measure the contamination level.
Teesworks then agreed to carry out remedial work to clean up the contamination that had been caused by the dredging.
Where contamination was found, remediated and the levels of contamination are reported in the return for Condition 5.2.11 of Teesworks Marine Licence Number L/2021/00333/3 by Royal Haskoning DHV{footnote}[[this>Teesworks/Planning/MLA_2020_00506/MLA_2020_00506-PC1084-RHD-SB-EN-ME-EV-1145-Condition%205.2.11%20Note%20P03.pdf|PC1084-RHD-SB-EN-ME-EV-1145-Condition 5.2.11 Note P03.pdf]]{/footnote} and the contamination levels have been extracted into a spreadsheet{footnote}[[this>Teesworks/Planning/MLA_2020_00506/Tabula-PC1084-RHD-SB-EN-ME-EV-1145-Condition 5.2.11 Note P03.xlsx|Tables of river bed contamination]]{/footnote}.
{{this>Teesworks/Planning/MLA_2020_00506/images/MLA_2020_00506-PC1084-RHD-SB-EN-ME-EV-1145-Condition 5.2.11 Note P03-03.jpg}}
Surprisingly the remediation was only carried out in Zone 2, as Zone 1 was part of the wider capital dredging, but no remediation was planned for the area downstream of the exclusion zone and nothing has been done about the wider river.
The tables below show exactly how much contamination was increased even after removal of the excessive contamination caused by the enclosed dredging. 3 months elapsed between the completion of the enclosed dredging and remediation, so sadly the level of contamination in the river will considerably increased during this time.
===== Full Contamination Tables =====
Percent of original contamination levels. Negative figures are increases in contamination.
|Metals|Arsenic (As)|Cadmium (Cd)|Chromium (Cr)|Copper (Cu)|Mercury (Hg)|Nickel (Ni)|Lead (Pb)|Zinc (Zn)|
|SS03|-2|-26|-31|-37|-38|-6|-13|-24|
|SS04|1|-64|-34|-25|-27|-28|-37|-40|
|SS05|11|-36|-31|-29|-28|-24|-27|-24|
|SS06|-4|-33|-24|-21|-23|-18|-15|-10|
|PAHs|ACENAPTH|ACENAPHY|ANTHRACN|BAA|BAP|BBF|BENZGHIP|BEP|
|SS03|-202|-30|-17|-19|-27|-31|-22|-19|
|SS04|29|26|24|25|24|16|21|24|
|SS05|-58|-19|-9|-6|-9|-10|-5|-5|
|SS06|-3|-107|-25|-7|-1|-6|0|2|
|PAHs|BKF*|C1N|C1PHEN|C2N|C3N|CHRYSENE*|DBENZAH|FLUORANT|
|SS03|-28|10|0|3|-3|-18|-8|-14|
|SS04|21|43|42|41|37|26|29|29|
|SS05|-11|16|8|13|9|1|4|-6|
|SS06|2|15|3|18|22|2|6|3|
|PAHs|FLUORENE|INDPYR|NAPTH|PERYLENE|PHENANT|PYRENE|THC|
|SS03|-76|-29|-5|-24|-9|-35|64|
|SS04|28|16|37|-2|37|24|61|
|SS05|-16|-13|12|-9|5|-16|37|
|SS06|-19|-12|20|0|4|-6|69|
|PCBs|PCB 101|PCB 105|PCB 110|PCB 118|PCB 128|PCB 138|PCB 141|PCB 149|
|SS03|-60|-104|-31|-61|0|-84|13|-5|
|SS04|-23|-32|-10|-23|6|39|-27|21|
|SS05|-16|-21|-23|-28|-44|-19|-33|14|
|SS06|-26|-57|-19|-37|-33|3|-120|1|
|PCBs|PCB 151|PCB 153|PCB 156|PCB 158|PCB 170|PCB 18|PCB 180|PCB 183|
|SS03|-88|-61|0|-67|-20|-41|-89|5|
|SS04|-12|-20|10|11|-4|-13|-46|-5|
|SS05|-40|-24|0|-11|-8|-13|-44|-5|
|SS06|-68|-9|-160|-200|-68|-28|-62|-40|
|PCBs|PCB 187|PCB 194|PCB 28|PCB 31|PCB 44|PCB 47|PCB 49|PCB 52|
|SS03|-40|-35|-27|-54|-23|-65|-76|-45|
|SS04|-2|-45|-10|-34|5|-24|-33|-18|
|SS05|-29|-40|-16|-43|-5|-59|-41|-23|
|SS06|-54|-85|-11|-46|-43|-94|-54|-32|
|PCBs|PCB 66|
|SS03|-52|
|SS04|-20|
|SS05|-32|
|SS06|-48|
|OrganCl|AHCH|BHCH|GHCH|DIELDRIN|HCB|PPTDE|PPDDE|PPDDT|
|SS03|90|64|81|45|-789|-63|-833|-233|
|SS04|76|61|75|61|-756|15|-507|52|
|SS05|83|50|71|35|-739|-30|-587|43|
|SS06|72|39|72|40|-1056|-16|-660|-200|
|ButylTin|Dibutyltin (DBT)|Tributyltin (TBT)|
|SS03|13|-41|
|SS04|0|0|
|SS05|-35|7|
|SS06|0|0|
===== Footnotes =====
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