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river_tees_contamination_excluded_areas_and_sampling

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river_tees_contamination_excluded_areas_and_sampling [2026/09/07 23:15] – [River Tees Contamination, Excluded Areas and Sampling] nefcadminriver_tees_contamination_excluded_areas_and_sampling [2026/09/08 10:34] (current) – [Other Pages That Link To This Page] nefcadmin
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 PD Ports marine licence application [[MLA-2025-00263|MLA/2025/00263]] supplied only 31 samples for both the Port of Hartlepool and the River Tees as specified by the sampling plan supplied by the MMO on the recommendation of Cefas. PD Ports marine licence application [[MLA-2025-00263|MLA/2025/00263]] supplied only 31 samples for both the Port of Hartlepool and the River Tees as specified by the sampling plan supplied by the MMO on the recommendation of Cefas.
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-{{ :260902mla202500263dredgearea.png?nolink&600 |}} 
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-^Dredge Parameter^Value^ 
-|Total dredged area of the River Tees|1162.37Ha| 
-|Total excluded area from dredging|10.61Ha| 
-|% of total dredged area excluded|0.91%| 
-|Area of smallest excluded area|0.8Ha| 
-|% of total dredged area made up by smallest excluded area|0.07%| 
-|Number of times smallest excluded area fits into total dredge area|1453| 
  
 The licence was granted with just 27(31 if 4 are included for Hartlepool) samples taken over the whole 1162.37Ha area, meaning that there was only **1 sample for every 43.05Ha** or **1 sample for every 62 football pitches**.  The licence was granted with just 27(31 if 4 are included for Hartlepool) samples taken over the whole 1162.37Ha area, meaning that there was only **1 sample for every 43.05Ha** or **1 sample for every 62 football pitches**.
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 The table above just drives home that 27 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 table above just drives home that 27 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.+The number of times an area fits into the total dredge area is dramatic, for the smallest excluded area  of 0.8Ha it fits 1453 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.
  
 4,600 samples is the maximum number for the river and in fact by using knowledge of the river the number of samples necessary can be reduced considerably but not to 27. 4,600 samples is the maximum number for the river and in fact by using knowledge of the river the number of samples necessary can be reduced considerably but not to 27.
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 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 uses the amount to be dredged to recommend 31 samples for a uniform volume of dredged material (i.e. a deep capital dredge), whereas the area table recommends 581 samples to provide spatial representation appropriate for a large area port 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 uses the amount to be dredged to recommend 31 samples for a uniform volume of dredged material (i.e. a deep capital dredge), whereas the area table recommends 581 samples to provide spatial representation appropriate for a large area port maintenance dredge.
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 ===== MLA/2015/00088 ===== ===== MLA/2015/00088 =====
  
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 [[River Tees Contamination, Excluded Areas and Sampling]] [[River Tees Contamination, Excluded Areas and Sampling]]
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river_tees_contamination_excluded_areas_and_sampling.1788822946.txt.gz · Last modified: by nefcadmin