Dredging the Stroudwater

Over a mile of the Stroudwater Navigation between St Cyrs Church and Ryeford Double Lock is now cruisable!

 

 

 

 

 

 

 

 

The Land & Water dredging team reached the fixed bridge at the rear of St Cyrs Church on Friday 4th March.

David Jowett took this excellent picture there on Friday. Click on either image to enhance the view.

The Land & Water dredging machinery and its operators have certainly dealt with an awful lot of mud, silt, slurry and an ever-growing pile of what is known in the trade as non-organic.

They have also dealt with dozens of enquiries from towpath walkers and cyclists who have been fascinated by the activity that has turned a shallow length of weed-choked water into a navigable waterway. 

The dredging process is described here: 

The Dredger

David, from North Wales, drives the pontoon-mounted excavator seen through the bridge in the distance. This is held steady by hydraulic legs that extend through the pontoon to the bottom of the canal.

The bucket scoops over 25 years of detritus from 1.1metres beneath the surface.

The bucket then tips its contents into a mud hopper or mud barge.

The Tug & Hoppers

Next, Ben the Tug arrives driven by Gary from Kent. It pushes an empty hopper. The tug has a draft of 3ft 6in with a ninety horsepower engine turning a 2ft 6in diameter propeller. Progress was halted on a couple of occasions when that propeller was stopped turning by tree stumps and barbed wire. There are two mud hoppers; one holds 25 cubic metres the other holds 16 cubic metres of material.

Having released the empty hopper Gary drops the hydraulic powered towing hoop over a bollard on the stern of the loaded one.

The tug then chugs off to the unloading wharf pushing the laden hopper, low in the water, ahead of it. The whole assembly makes very good headway along the canal, especially when one considers the depth of the tug’s keel and the obvious weight of its loaded hopper. Gary’s skill at the helm means that there is little need to slow down through the bridges.

The Unloading Wharf

On arrival at the unloading wharf, the tow hoop is lifted from the hopper. A long reach excavator on the bankside, driven by David's son Iwan, gently pulls the hopper to the side. Iwan scoops the black and slimy stuff from the hopper to deposit it onto, what looks like, a huge sloping & shaking barbecue grid.

This is the 800 horsepower engined Screening Machine. The grid vibrates rapidly. This has the effect of sorting the solids from the silt. The silt drops into a holding pit. The solids slide forward onto the ground.

Spreading the Silt

Yet another long reach excavator scoops the silt from the holding pit before tipping it gently into the hopper of an enormous four-wheel drive dumper truck. This one is driven by Micha who hales from Rumania. The truck scrambles away from the wharf to tip its load onto the adjacent field. This gives the pastureland a 4-6” deep covering of high nutritional value topsoil.

As good for the soil as the sorted silt obviously is, the tipping of this stuff on agricultural land came about only after a long process of research and examination carried out by the boffins back at Land & Water's head office in Guildford. Their research & planning satisfied the Environment Agency's demanding standards and a licence was duly granted. Incidentally the Screening Machine process is also the subject of Environment Agency scrutiny and licensing.

The spreading continues throughout the process… In the meantime, the non-organic pile grows apace.

What was found

During the early stages of the operation, Land & Water Project Manager Chris Walker expressed surprise at the absence of tyres and shopping trolleys in the canal. These are the usual bounty drawn from the depths he explained. Rubble and building waste was in evidence though.

The non-organic pile is jet washed and sorted for subsequent disposal at appropriate locations. Some tyres did surface late in the project. They are treated as hazardous waste. The Land & Water team’s findings showed that throwing unwanted wheels and tyres into the waterways of Britain is not a modern malaise. A set of four iron rims fitted with solid rubber tyres, the sort that might long ago have been fitted to a crane or steam powered vehicle, have been recovered.

The pile of tangled metal will finds it way to a scrap yard.

Care & Knowledge

The work carried out by this team of professionals has indeed been interesting to witness. Chris and Gary paid a Saturday visit to the Visitor Centre at Wallbridge Lock recently. They commented on the friendliness of the local people who regularly gave them the thumbs up sign. Chris observed… “They are obviously very pleased to see the restoration… mind you wherever we go in the country canal walkers, bikers and boaters always have a smile for us”. When asked about wildlife and ecological issues Chris spoke at length about the preparations made and care taken as well as his own love and knowledge of wild birds. “We care as much about the wildlife as we do about the lives of our people,” Chris said without embarrassment. It certainly seemed that way on our regular visits.

The Land & Water people are the sort of team whose leader has a bird table outside the window of his Portakabin office!