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Sealed for success

Construction of the UK’s canal network was an amazing engineering feat, but when it comes to restoration, sometimes modern methods have to be called on. Claire Symes visits the Wey & Arun Canal to find out more.

Canals have become a key focus for leisure activities in the UK, whether people cruise along them in boats or appreciate them by foot or cycle from the towpath.

But they were once the arteries that provided transport to drive the industrial revolution.

At the turn of the last century with an expanding railway network and development of the motor car, canals fell out of favour and started to fall into disuse.

Many canals have since been fully restored, but the rehabilitation of the Wey & Arun, which runs between the North and South Downs in Surrey and West Sussex, is still very much a labour of love. This canal once connected the River Wey at Guildford with the Arun at Pulborough.

Volunteers have been working to restore it since 1971 using traditional techniques wherever possible, but recent work to seal a section of the route near the village of Loxwood called for a more modern approach.

Work to reseal a section of the canal north of Loxwood has extended one of its navigable sections to enable boat trips that run south from the wharf at Loxwood to start operating northwards too.

Traditionally, canals were lined with puddled clay that was so called because the navvies used their bare feet to consolidate puddles of clay into a layer across the canal.

“Historical records show that the navvies got an extra payment for carrying out this work in winter conditions,” says Wey & Arun Canal Trust chief engineer John
Talbot.

Many canals in the UK are still lined with puddled clay - some of it original - but the Wey & Arun was built on a shoestring budget and in many areas the clay is just not thick enough.

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This is where modern engineering solutions come in. The Wey & Arun Canal Trust has used geosynthetics to reline the Loxwood Pound - the section above Loxwood lock and below Devil’s Hole lock.

This is mainly due to the quality of the clay lining, but also because this section of the canal runs next to a tributary of the River Arun and the canal channel was cut through a former ox bow of the river, so there were gravel deposits that were allowing large volumes of groundwater to flow in during the winter and drain the canal in the summer.

“The level of leakage was serious - we could lose two lockfulls of water in 24 hours,” says Talbot. “Most of the Loxwood Pound is cut through the Weald Clay but the former river channel had left lenses of sand and gravel within the canal channel. There is a winding hole in this section, which may not have been purpose built for turning boats but actually have been from where sand had been extracted.”

At present, with just a short section of the canal open, the trust uses pumps to rebalance the water levels, but with high levels of leakage above Loxwood lock, this solution was not viable.

The trust has been aware of the issue in this area for some time and a plastic sheet style geosynthetic was installed 10 or 15 years ago to try to solve the problem. This hasn’t proved successful in the long term.

“The level of leakage was serious - we could lose two lockfulls of water in 24 hours.”

This time Talbot worked with marine contractor Land & Water Services, which supplied materials, machines and operators to the trust on a cost basis, to complete the scheme to seal the canal.

Work focused on the 40m section where the stream was known to have been diverted during the canal construction.

With water drained fully from the section, Land & Water Services excavated 1m of material from the canal channel and then lined the canal with 5m wide rolls of Maccaferri’s Bentomat, which were overlapped by 200mm and filled with bentonite pellets to create a seal, before material was backfilled and compacted over
the top.

Pre-seed coir matting was placed on the banks of the canal to prevent erosion.

Improvements to another 200m section of the Loxwood Pound have also been carried out.

With work at Loxwood complete, Talbot is looking ahead to the next big projects, but the difficulties with land ownership mean that work cannot always be planned just with the needs of the canal in mind.

The trust doesn’t own any of the property so restoration is a carefully balanced exercise in negotiation.

Some landowners are happy to lease the land to the trust and then occasionally hand the land over, while others are resistant to the restoration work so the trust is focusing on areas where owners are amenable and hoping those against the redevelopment will change their minds by the time restoration of those sections becomes vital.

One big step forward in the restoration plan is about to take place with an agreement in place with Surrey County Council to buy - for a nominal fee - some land at the northern end of the canal that would enable it to be reconnected to the River Wey at Guildford.

“The original canal was completed in four years, 200 years ago, when the only mechanical means available would have been a steam pump”

In this section residential properties have been built over the original route so the new land would enable a diversion to be built to reconnect the canal.

This scheme would also open up the possibility of allowing private craft on to the canal for the first time in decades and offer the potential for the trust to rent or lease out moorings to boost its funds.

“There is also the potential for a marina to be developed along the route,” says Talbot.

Other major work underway includes dredging of 8,500m3 of material from a section near Dunsfold Aerodrome - made famous by its use as Top Gear’s test track. Here the dredged material will be spread over a field the trust has rented for the purpose.

“Once the leaves have rotted down, the field will be more fertile than when we took possession, so the land owner is happy with the arrangement,” says Talbot.

Although a report by Atkins suggests the canal could be restored in 20 years with funding of £94M at 2007 levels (see box), Talbot believes 30 to 40 years is more realistic.

Even with the significant contribution to costs from volunteers, there are still the challenges of fund raising, planning issues and land ownership to overcome.

“It is a salutary lesson to reflect that Josias Jessop - son of the illustrious William Jessop - and May Upton completed the original canal in a mere four years, some 200 years ago, when the only mechanical means available would have been a steam pump,” says Talbot.

A passage to restoration

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The canal was once almost 37km long and was built between 1813 and 1816 as route to transfer materials from London to the south coast without having to go by sea and run the gauntlet of the English Channel with the risk of running into Napoleon’s forces gathered there.

The canal created the possibility of supplies reaching the coast in two days rather than several weeks at sea.

It fell into disuse in the 1870s partly because England was at peace with France, partly because railways had started to be developed and also because the canal suffered from technical problems and the summit of the route just south of Cranleigh was sometimes dry for weeks at a time over the summer months.

Work on restoring the canal started in 1971 but progress has been slow for several reasons: the work is being undertaken by volunteers, it is funded through donations, and because of land ownership issues.

So far around a third of the canal has been restored but not all of the sections are connected yet, so day cruises currently only run from Loxwood.

A report by Atkins in 2006 suggested that it would take another 20 years to restore the full route at a cost of £94M, but that with the benefit of a volunteer workforce the cost would be nearer £64M.

To achieve this, Atkins said the Wey & Arun Canal Trust should work on three major projects and several smaller ones at a time rather than focusing its efforts on one area.

Geotechnical engineer John Talbot is the man charged with ramping up the work, although it is supposed to be his retirement project as he took on the role of chief engineer after retiring from Hyder in 2009.

“The Wey and Arun is being restored as a broad beam canal with locks widened as they are rebuilt as part of the initiative to create a navigable waterway from Kendal in Cumbria to the south coast of England,” says Talbot. In addition to the funding, planning and land ownership issues, the trust also has to consider the environmental implications of the restoration work.

The River Arun to the south is a Site of Special Scientific Interest (SSSI) and the canal runs through three woodlands that are classified as SSSIs.

To the north the canal runs close to the Cranleigh Stream, a tributary of the Wey, which connects to the Thames and connection of the canal would create a pathway for American Crayfish and Zander to enter the canal, potentially putting the Arun’s waters at risk.

“We need to keep the waters separate and we are looking at the options available,” says Talbot. “A dry dock or boat lift between the two sections could provide a solution but both still carry environmental risks.”

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