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Post by Deleted on Jul 28, 2020 6:10:16 GMT
Water injection dredging is quite interesting. "THE METHOD Water injection dredging is one of a number of hydrodynamic dredging techniques, where the basic principle is to remobilise the sediments, using the action of natural currents. Water injection dredging uses water pumps connected to a series of nozzles on a horizontal jet bar. The nozzles inject large volumes of water at low pressure directly onto the sediment build up. This process fluidises the sediment build up, turning it into a density current which remains close to the water bed. The sediments are then picked up by this current and able to flow horizontally out of the channel or port. This process eliminates the need for traditional excavation dredging methods and the subsequent transportation of the dredged material. Nature takes care of the sediment transport, making water injection dredging a cost-effective dredging technique with less impact on the environment." themarinegroup.co.uk/boatyard/dredging/
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Post by JohnV on Jul 28, 2020 6:25:17 GMT
Water injection dredging is quite interesting. Nature takes care of the sediment transport, making water injection dredging a cost-effective dredging technique with less impact on the environment." themarinegroup.co.uk/boatyard/dredging/and avoids the EU ruling that makes you have to treat it as hazardous waste
Morning Andrew, lovely morning here with bright sunshine. Hope you are having the same on the Thames
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Post by kris on Jul 28, 2020 6:32:24 GMT
Water injection dredging is quite interesting. "THE METHOD Water injection dredging is one of a number of hydrodynamic dredging techniques, where the basic principle is to remobilise the sediments, using the action of natural currents. Water injection dredging uses water pumps connected to a series of nozzles on a horizontal jet bar. The nozzles inject large volumes of water at low pressure directly onto the sediment build up. This process fluidises the sediment build up, turning it into a density current which remains close to the water bed. The sediments are then picked up by this current and able to flow horizontally out of the channel or port. This process eliminates the need for traditional excavation dredging methods and the subsequent transportation of the dredged material. Nature takes care of the sediment transport, making water injection dredging a cost-effective dredging technique with less impact on the environment." themarinegroup.co.uk/boatyard/dredging/ carts favoured technique is to use the natural flow of the river, along with the passage of boats to move the obstructions.
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Post by Deleted on Jul 28, 2020 6:35:06 GMT
Yes it's very nice. I tied to some random tree after dark last night which has some pleasant birdsong coming from it this morning.
Seems to be reasonably sunny and less windy which is good.
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Post by JohnV on Jul 28, 2020 6:36:18 GMT
Water injection dredging is quite interesting. "THE METHOD Water injection dredging is one of a number of hydrodynamic dredging techniques, where the basic principle is to remobilise the sediments, using the action of natural currents. Water injection dredging uses water pumps connected to a series of nozzles on a horizontal jet bar. The nozzles inject large volumes of water at low pressure directly onto the sediment build up. This process fluidises the sediment build up, turning it into a density current which remains close to the water be carts favoured technique is to use the natural flow of the river, along with the passage of boats to move the obstructions. Morning Kris .... that would (and used to) work when there were lots of big loaded boats moving but as they are so much against commercial carrying .............
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Post by kris on Jul 28, 2020 6:38:22 GMT
carts favoured technique is to use the natural flow of the river, along with the passage of boats to move the obstructions. Morning Kris .... that would (and used to) work when there were lots of big loaded boats moving but as they are so much against commercial carrying ............. exactly, I’ve not seen any evidence of the dredging on the Trent starting yet, so it all maybe at some unspecified time in the future.
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Post by TonyDunkley on Jul 28, 2020 7:46:53 GMT
guess it depends on the draught.. Do they dump the dredged stuff or do they have to treat it? They just let it go, to flow down stream if they are spot dredging. and : Yes, at the pinch points. But the immediate problem is solved, which is what cart are all about. No, that's simply not so, . . except for the all too infrequent occasions nowadays when C&RT make a token effort to remove the mud and silt build-up from ABP's waters in the lock tail at Keadby ! Why post vague, misleading, and remotely factual generalizations which come nowhere near to answering a specific question on how C&RT have previously disposed of the vanishingly small amounts of material they have dredged from sections of the Trent during the time for which they, . . God help us, . . have been the navigation authority ? Maintaining a dredged to minimum depth navigation channel in the Trent from Wilden Ferry - the upper limit of navigation at Shardlow - to Gainsborough Bridge - the lower limit of Trent Navigation Company, British Waterways, and now C&RT's jurisdiction is, and always has been, a complex and multi-faceted process which until the cessation of the last of the river's commercial traffic on the lower reaches in July 2013 was always complimented by the natural scouring action of the river's run-off current and the (Ebb) tide and the regular disturbance of riverbed silt and sand by the passage of deep-draughted commercial traffic. The practice of 'spot dredging' was never really applicable to the Trent in the same sense as it was used on canals to clean out the shallow spots adjacent to lock scours and where streams, drainage channels and feeders routinely carry land run-off silt into the waterway every time it rains. Prior to BWB's progressive abandonment of routine maintenance dredging on any part of the Trent - which began in earnest some 35(+) years ago - the closest form of routine maintenance 'spot dredging' practiced on the Trent was the urgent and immediate removal from the lock tails at Holme, Stoke, Gunthorpe, Hazleford, Newark (Bottom Lock) and Cromwell, the sand and silt deposited by the floodwater in the lock tail back-eddies, and this process always began as soon as the river level dropped to no more than 4' - 5' above normal immediately below each of the affected locks. Except for Cromwell Lock - for obvious reasons - the material removed from the lock tails immediately after any serious flooding events was dumped back into the river just above the next downstream weir, ready to be carried away further downriver by the current during the next serious floods. Formerly this was done using drop(bottom)-hoppers, and in later years from hoppers emptied with a craneboat secured close to the weir crest. For preference, so that the larger proportion of the deposited material was carried away by the next serious flood over the far end of the weir and away downriver instead of simply being carried over the lock end of the weir and re-deposited in the lock tail, the 'dropping down' bollards situated above all the Trent weirs were used to secure the craneboat, rather than the bullnose bollard at the top end of the lock-islands. The majority of the Trent, including the 26 miles from Cromwell Lock to Gainsborough was routinely dredged, with a fleet of three bucket dredgers - Top, Middle, and Bottom Dredgers - permanently allocated to and working on different sections of the river. Natural scouring by run-off water, or the Ebb plus run-off water, assisted by the passage of loaded commercials, kept most of the total mileage of navigation channel deep and clear, and the dredgers were stationed for lengthy periods at locations where waterborne sediment, including gravel in times of especially severe flooding, was known to consistently settle out due to reductions in the speed of the Ebb and the current brought about by changes in the river's cross-section and bed profile. During each lengthy spell at these carefully chosen locations a large deep hole, sufficient to hold many thousands of tons of waterborne sediments was dredged out in the river bed to act as a reservoir for the material which the river would deposit there prior to the return of the dredger several months later. All the material dredged from the river by the bucket dredgers was transported to and unloaded into designated dredging tips at Gunthorpe, Hazleford, Cromwell, and Marton.
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Post by kris on Jul 28, 2020 12:17:50 GMT
Yawn.
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Post by TonyDunkley on Jul 29, 2020 8:02:39 GMT
so does it then silt up further down? . . . . . Yes, [it does silt up further down] at the pinch points. In relation to silting of any part of the Trent caused by major flooding of the sort we had last Winter, . . . what exactly do you mean by the term - "pinch point" ?
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Post by naughtyfox on Jul 29, 2020 9:24:35 GMT
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Post by TonyDunkley on Jul 29, 2020 20:02:37 GMT
What I need is a map of all the Trent ''pinch points'' which, according to Kris, collect all the sand and silt that gets carried into the river by Winter floods ! Until he mentioned it, I had no idea that the Trent was full of these ''pinch points'', or that the river contains large quantities of this remarkable buoyant sand that will ''flow downstream'' in normal river conditions until it stops and settles onto the river bed at one of these pinch points.
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Post by naughtyfox on Jul 29, 2020 20:32:03 GMT
What I need is a map of all the Trent ''pinch points'' I just stuck that map up as not all may be familiar with it. Seven years ago I didn't know much about the navigable inland waterways of England, I hadn't watched videos of narrowboats going along the Trent or the Thames, not sure if I had even heard of the Rivers Soar, Kennet or Cherwell. The Trent is on our plan for the future. Once kris has pinpointed his pinch-points we'll aim for the middle and hope for the best!
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Post by Deleted on Jul 29, 2020 21:33:43 GMT
. . . . . Yes, [it does silt up further down] at the pinch points. In relation to silting of any part of the Trent caused by major flooding of the sort we had last Winter, . . . what exactly do you mean by the term - "pinch point" ? I met 'Humber Survey' on the Trent on Monday, so something going on, I am interested in these discussions btw Jo PS won't all the silt from the Trent end up in the Humber?
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Post by JohnV on Jul 30, 2020 5:53:36 GMT
In relation to silting of any part of the Trent caused by major flooding of the sort we had last Winter, . . . what exactly do you mean by the term - "pinch point" ? PS won't all the silt from the Trent end up in the Humber? Yes, but the tidal streams are so strong that although the channel shifts all over the place it stays clear
eventually it ends up in the North Sea. It's continuously surveyed and chart corrections issued, buoys are being moved all the time to show the deepwater channel
(Associated British ports control below Keadby and below Goole to the sea and boy does it show)
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Post by TonyDunkley on Jul 30, 2020 6:19:32 GMT
What I need is a map of all the Trent ''pinch points'' The Trent is on our plan for the future. Once kris has pinpointed his pinch-points we'll aim for the middle and hope for the best! I'm sorry to have to disillusion you, Ross, but these so-called siltation/dredging ''pinch points'' are nothing but a figment of Kris's imagination, . . so whatever you do, don't be tempted to include anything about this fanciful tripe in any future plans which take you onto any part of the Trent ! There is, and only ever has been, one genuine 'pinch point' on the Trent between Gainsborough and Nottingham and it has nothing whatsoever to do with siltation, dredging, or depth of water. It's the market town of Newark, and the constraints on vessel size - 150' LOA x 20' Beam - imposed on navigation upriver of that point by the sharply angled entrance basin to Newark Bottom (Nether) Lock, which forces a 45 degree turn in a distance of only 160' into the ('new' - 165' x 30') lock from the straight ahead line of the run-in to the old original 82' 6'' x 15' Trent size lock.
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