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--- cefas_thoughts_about_the_river_tees_over_time [2025/12/22 21:38] – [Cefas 30th July 2024] nefcadmin
+++ cefas_thoughts_about_the_river_tees_over_time [2025/12/28 23:19] (current) – [Cefas 5th October 2023] nefcadmin
@@ Line 146: / Line 146: @@
 This response was prepared just after the initial crustacean die-off had occurred in the River Tees and the local coast.
-==== Cefas 2023 ====
+==== Cefas 26th July 2023 ====
+==== Cefas 5th October 2023 ====
@@ Line 166: / Line 170: @@
 Measurements were required from all 31 sites: Particle Size Analysis (PSA), Trace metals (including arsenic), Organotins (tributyltin and dibutyltin), Polycyclic Aromatic Hydrocarbons (PAHs), Polybrominated diphenyl ethers (PBDEs), Total Organic Carbon (TOC).  10 sites also needed to measured for Polychlorinated Biphenyls (PCBs) – must include a sample collected from Chart sectors 1 & 2 (Figure 1), Organochlorine pesticides (OCs) – must include a sample collected from Chart sector 1 & 8, Navigator North Tees and Hartlepool Berths (Figure 1).
-=== MMO Covering Letter for Cefas 25th January 2025 ====
+==== MMO Covering Letter for Cefas 25th January 2025 ====
 [[https://www.northeastfc.uk/RiverTees/Planning/MLA_2015_00088/Returns/Post_Consent_Discharge%20MLA201500088%20CP_.pdf|L/2015/00427/7 Mid Licence Sediment Sampling Review – Condition 5.2.3]]
+The MMO considered that the sample results submitted discharged the conditions on the licence.  However, the levels of BDE209, 99 and 100 were noted as being higher than lower assessment criteria (LAC) but lower than the high assessment criteria (HAC) and as the applicant had not measured total organic carbon (TOC) as requested it was not possible to normalise the values.  So the MMO requested annual measurements of BDEs in future.
+Cefas comments on particle size were based on the mass particle size distribution, so stated that all but 2 of the samples were similar.  A comparison based on area particle size distribution would have seen less difference between all the samples.
+All trace metals (including arsenic) showed levels greater than Cefas Action Level 1 (AL1) (beige markers on maps) in multiple samples, but no samples were greater than AL2.
+{{ :251215-2410separatemetals.png?nolink&600 |}}
+There is only an AL1 for individual polycyclic aromatic hydrocarbons (PAHs), so the maps for the individual PAHs are colour coded as green when below AL1, beige when between AL1 and 10*AL1 and red when greater than 10xAL1.
+{{ :251215-2410separatepahs.png?nolink&600 |}}
+As there is no AL2 for PAHs Cefas uses the Gorham-Test protocol to examine sums of low molecular weight (LMW) and sums of high molecular weight (HMW) PAHs.  The sum of each are assessed against effect range low (ERL) below this the sediment is low risk and effects-range median (ERM) above which the sediment is considered of high risk.
+"Out of the 31 samples analysed for PAHs 29 were greater than the LMW ERM ranging from around the ERL threshold (3,160 µg/kg) to 4.4x the ERM threshold (14,047 µg/kg). The remaining two samples were 1 (Figure 1 Exolum Riverside) and 27 (Figure 1 Chart 12); sample 1 contained LMW PAH levels greater than ERL but close to the ERM threshold whilst sample 27 contained levels of LMW PAHs less than ERL. Only one sample, sample 6 (Figure 1 Chart 3), was close to, but below, the ERM threshold for HMW PAHs. All remaining levels of HMW PAHs were below the ERM except for three samples which were below the ERL. The three samples below ERL were sample 24 (Figure 1 Chart 9), sample 27 (Figure 1 Chart 12) and sample 28 (Figure 1 Hartlepool Channel). Of note is that sample 27 is the only sample to contain levels of both LMW and HMW PAHs below their respective ERLs."
+{{ :251215-2410lmw-pahs.png?nolink&200 |}}
+{{ :251215-2410hmw-pahs.png?nolink&200 |}}
+"**The levels of LMW PAHs alone would normally preclude the material from continued disposal to sea due to levels that would pose a risk to the marine environment**, however, the river Tees is historically an area that exhibits PAH levels higher than other UK rivers due to industrial sources and history of the river (Nicolaus et al., 2015; Kirby et al., 1999), especially acute LMW PAHs. This has been evident throughout the current licence whereby both LMW and HMW levels detected in sediment sampling and analysis since 2015 have shown elevated levels of LMW and HMW PAHs that are greater than their respective ERLs and ERMs (documents cited in paragraphs nine and ten). It is prudent to compare the current results to historical levels detected within the duration of the licence so that local and regional context of these results are considered; these are visualised in Figures 4 and 5 below."
+{{ :250130mla201500088-mmoresponsefigure4.png?nolink&400 |}}
+{{ :250130mla201500088-mmoresponsefigure5.png?nolink&400 |}}
+Cefas basically say these high levels are not an issue, despite most of the samples having LMW PAHs above ERM and as Cefas said any sample above ERM "can be considered higher risk, with more likelihood of harm occurring."  As such this material should not have been considered safe for disposal at sea, but ....
+"It is observed that levels of LMW PAHs have maintained a similar level since 2023; the minimum value is less than 2023, the median and mean are of a similar value to 2023 but the maximum has increased since 2023. Viewing the levels of LMW PAHs since the start of the licence in 2015 indicates that they have continued to drop over the years with the Tees and Hartlepool dredge area. Interpretation of the HMW PAH levels is more clear cut with all factors (min, median, mean and max) all decreasing in value since 2015, and in broader terms all seeing a decrease every year since 2019."
+"Considering these results holistically; in both the local context of the river Tees and in comparison, to previous mid-licence data, the PAH results alone do not preclude material from continued disposal to sea, in this case to Tees Bay A (TY160) disposal site."
+Neither Cefas figure 4 or 5 show the ERL or ERM levels, but when the ERM level is shown on figure 4, it is obvious that these samples present a significant risk of harm to the marine environment:
+{{ :250130mla201500088-mmoresponsefigure4-erm.jpg?nolink&400 |}}
+This chart without the ERM level was reproduced in the Tees MDP Baseline Document to show how the Tees was getting better, which may be the case, but continued dredging and dumping will still be doing damage and as such should be curtailed.
+Surprisingly only low concentrations of PCBs are seen in the samples and only a few organochlorine samples were found to be above German AL1, as the UK has no AL2.
+Polybrominated diphenyl ethers were a different story with BDE 209, 99, 100 and 85 show levels that are of concern.  Once again averages were used to appear to minimise the issue, however as stated "It should be noted that the sampling numbers for each year vary for PBDEs and therefore differences could be due to sampling variation e.g. 2023 had ten samples, 2021 had nine whilst 2024 and 2019 had over 30 samples each which will affect averages and thus results are not directly comparable."  There are far too few samples taken to be able to make a sensible statistical analysis not only of BDEs but all the chemicals as the spatial area of dredging is so large.
+Once again dredging is allowed to continue with disposal of this material to sea: "Given the above, levels of PBDEs pose a high risk to the marine environment at some sites. Overall, my opinion is that **the levels of BDE209 and BDE99 observed in the 2024 data pose a potentially unacceptable risk to the marine environment.** However, the levels for all other BDE congeners and other contaminants analysed do not preclude the material from disposal to sea. Given that **the levels of BDE209 and BDE99 appear to be lower or generally consistent with the levels observed in previous years (excluding the BDE99 maximum)** and given that the **elevated presence of PBDEs in the river Tees that can be traced to historic industrial inputs** the **material whilst of concern may be allowed for disposal, in this case to Tees Bay A (TY160) disposal site.** However, to evidence the impact of the disposal activity with contaminants at these levels it would be prudent to undertake a site-specific monitoring survey to look at impacts in the sediment flora and fauna around the area of the disposal site. I recommend that Tees Bay A (TY160) disposal site and the wider area, is flagged for future monitoring by the MMO."
-=== MMO Quoting Cefas 1st Arpil 2025 ====
+==== MMO Quoting Cefas 1st Arpil 2025 ====
 [[https://www.northeastfc.uk/RiverTees/Planning/MLA_2025_00263/Additional%20Documents/MLA2015000886_R11.1%20Decision%20Letter.pdf|L/2015/00427/7 Mid Licence Sediment Sampling Review Resubmission – Condition
 .2.3]]