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--- river_tees_areas_excluded_from_dredging [2026/09/06 22:44] – [MLA/2025/00263] nefcadmin
+++ river_tees_areas_excluded_from_dredging [2026/09/08 10:32] (current) – nefcadmin
@@ Line 1: / Line 1: @@
-====== Areas Excluded from Dredging ======
+===== River Tees Areas Excluded from Dredging =====
-===== MLA/2025/00263 =====
 The River Tees has a heavy industrial history of over 150 years and because of this has one of the most contaminated riverbed sediments of any port in the UK.
-While the names of excluded areas where the river was considered too toxic to dredge where specified in both [[MLA-2025-00263|MLA/2025/00263]] and the previous 10 year licence application [[MLA-2015-00088|MLA/2015/00088]], the exact coordinates were not specified.  These were added after [[MLA-2025-00263|MLA/2025/00263]] was granted when a judicial review highlighted this error in granting the licence.
+While the names of excluded areas where the river was considered too toxic to dredge were specified in both [[MLA-2025-00263|MLA/2025/00263]] and the previous 10 year licence application [[MLA-2015-00088|MLA/2015/00088]], the exact coordinates were not specified.  These were added after [[MLA-2025-00263|MLA/2025/00263]] was granted when a judicial review highlighted this error in granting the licence.
+{{ :260907excludedareasonly.png?nolink&600 |}}
-{{ :260902mla202500263dredgearea.png?nolink&600 |}}
+The total area excluded from dredging is less than 1% of the total area currently licenced to be dredged [[MLA-2025-00263|MLA/2025/00263]].
+^  #  ^  Name  ^  Area Ha  ^
+|  1  |  Britannia Wharf and Enterprise Zone  |  0.80  |
+|  2  |  Cochranes Tees Wharf - Normanby Wharf Graving Dock  |  7.83  |
+|  3  |  Tees Offshore Base - Tees Commerce  |  1.13  |
+|  4  |  Wharf(TPC) Dry Dock  |  0.85  |
+|  All  |  Total Area  |  10.61  |
+{{ :260902mla202500263dredgearea-excludedareas.png?nolink&600 |}}
+The smallest excluded area is Britannia Wharf and Enterprise Zone is only 0.8Ha.
 ^Dredge Parameter^Value^
@@ Line 18: / Line 28: @@
 |Number of times smallest excluded area fits into total dredge area|1453|
-PD Ports marine licence application [[MLA-2025-00263|MLA/2025/00263]] supplied only 31 samples as specified by the sampling plan supplied by the MMO on the recommendation of Cefas.
+The total currently licenced dredge area is 1,453 times the size of the smallest area excluded.  Looking for contamination localised at this scale in the licenced dredge area is very much the proverbial looking for a needle in a haystack.
-The licence was granted with just 31 samples taken over the whole 1162.37Ha area, meaning that there was only **1 sample for every 37.50Ha** or **1 sample for every 54 football pitches**.
-{{ :260902mla202500263dredgearea-excludedareas.png?nolink&600 |}}
-^  #  ^  Name  ^  Area Ha  ^  % Total Dredge Area  ^  # Fit Into Total Dredge Area  ^  # Fit Into Single Sample Area  ^
-|  1  |  Britannia Wharf and Enterprise Zone  |  0.80  |  0.07  |  1452.96  |  46.87  |
-|  2  |  Cochranes Tees Wharf - Normanby Wharf Graving Dock  |  7.83  |  0.67  |  148.45  |  4.79  |
-|  3  |  Tees Offshore Base - Tees Commerce  |  1.13  |  0.10  |  1028.65  |  33.18  |
-|  4  |  Wharf(TPC) Dry Dock  |  0.85  |  0.07  |  1367.49  |  44.11  |
-|  All  |  Total Area  |  10.61  |  0.91  |  109.55  |  3.53  |
-The table above just drives home that 31 samples would have been drastically insufficient to be able to detect the current excluded areas and as such will not be able to detect similar currently unknown highly toxic areas within the total dredge area.
-The number of times an area fits into the total dredge area is dramatic, for the smallest excluded area  of 0.8Ha it fits 1452 times.  While this sounds like a lot of samples in fact to be sure of finding such small areas then the best approach would be adopt a grid and divide the dredge area into 50m squares and taking a sample in the middle each square.  This would give a greater than 95% chance of detecting all the 0.8Ha, but would require over 4,600 samples.
-,600 samples is the maximum number and in fact by using knowledge of the river the number of samples necessary can be reduced considerably but not to 31.
-The Cefas justification for 31 samples rather than working from a high number instead takes historical precedent, economic costs as the justification and the OSPAR volume table.  Where the OSPAR volume table rather sets a minimum number of samples which should be taken for anything other than a deep capital dredge when read in context and so this number is inappropriate for a large area maintenance dredge.
-The OSPAR guidance states that both spatial and volumetric representation must be achieved.  To this end, the OSPAR guidance provides two tables, the volumetric table which use the amount to be dredged to suggest the number 31, whereas the area table suggests 120 samples.
-===== MLA/2015/00088 =====
-{{ :260902mla201500088dredgearea.png?nolink&600 |}}
-^Dredge Parameter^Value^
-|Total dredged area of the River Tees|1612.66Ha|
-|Total excluded area from dredging|10.61Ha|
-|% of total dredged area excluded||
-|Area of smallest excluded area|0.8Ha|
-|% of total dredged area made up by smallest excluded area||
-|Number of times smallest excluded area fits into total dredge area||
-{{ :260902mla201500088dredgearea-excludedareas.png?nolink&600 |}}
+This is explored more fully as the [[River Tees Contamination, Excluded Areas and Sampling]].
+===== Other Pages That Link To This Page =====
+{{backlinks>.}}