Wild Land News no 71, Spring/Summer 2008

An experimental toilet for Corrour bothy Article

by John Cant

There is a long history of shelters and bothies in the Cairngorms. However, in the latter part of the 20th Century many were removed, mostly on safety grounds, especially after the 1971 Curran disaster when 5 school children and a trainee instructor died trying to reach the Curran refuge on the plateau.

The Corrour hut in the Lairig Ghru remains; however, like many bothies, it faces the health hazards arising from the need by humans to answer nature's call. The Mountain Bothies Association, who maintain the Corrour bothy, are exploring an interesting new approach to dealing with this issue. MBA member, John Cant, explains further:

Corrour Hut, Lairig Ghru with the toilet in construction.
Photo: John Cant

Toilets at bothies are not unheard of - Ruighaiteachain in Glen Feshie has had a flush toilet and septic tank in place for years, Bob Scott's beautifully renovated bothy at Derry lodge has a septic tank, and the Linn of Dee car park has two composting toilets.

When it came to installing a toilet at Corrour, we initially thought it would just be a case of choosing the best technology for the job. Water flush toilets and septic tanks are well known, but they depend on having a supply of water, ease of access to install and empty the septic tank if necessary, and ground conditions to permit digging a big hole to take the tank.

Composting toilets are arguably the best technology for treating human excreta in all circumstances. Instead of polluting and wasting valuable water supplies by using water as a transport mechanism, the contributions are composted on-site and the proceeds are returned to the environment as a valuable manure.

A composting toilet works by having visitors add a handful of soak after each use, the soak being an absorbent carbon-rich material like sawdust or peat. The soak covers the contributions and keeps the pile aerated, reducing smells, and balancing the high nitrogen content of urine, making for a perfect mix that will compost itself, given half a chance.

The best-known composting toilet - the Clivus Multrum - is built as a vault with a sloping floor and a capacity about three times the volume of the yearly contributions. The contributions slide gently down the floor towards the exit, mouldering away in the process. If everything works perfectly the vault never has to be dug out.

A more basic possibility is the VIP toilet - the Ventilation Improved Privy : a hole in the ground with a seat on top and a vent pipe. When the hole is full, it is sealed and another one dug elsewhere.

For Corrour we quickly ruled out a flush toilet. We would never get a septic tank safely installed in the unremitting bog, and we couldn't rely on a supply of water in the depths of winter. We also had to rule out a composting toilet due to the need for a soak material and the size of the required construction.

Another of our design criteria was to build the smallest practical toilet so as to avoid adding another structure to the glen and so minimise the environmental impact. The bothy being built on bedrock meant that a vault constructed above ground level would end up dwarfing the bothy itself.

All that remained from our options, then, was the VIP. We weren't, however, terribly happy with this either - again, digging holes in bogs or bedrock is not easy, we didn't like the idea of another structure, nor did we like the idea of holes full of mouldering excrement.

The most significant design problem was unavoidable - people. People are used to public toilets being kept clean by paid staff. If something goes wrong and someone makes a mess, it is someone else's responsibility to clean it up. At an unstaffed bothy like Corrour, it is unfortunately all too easy to make a mess and walk away leaving the mess behind. Any sort of toilet is also likely to become a receptacle for rubbish of all sorts - biodegradable or not.

A bit of research came up with a sales brochure that suggested a possible solution to some of the difficulties : a geotextile bag. This works like a mini septic tank - the bag receives the contributions and its woven structure allows the liquid to pass through while retaining the solids. A bag could be slung below a toilet seat and detached, dried and stored whenever full, and the drainage could be run out to a small soak-away. Would this work if installed in a simple structure attached in the lee of the bothy? We didn't know, but thought it worthwhile to trial this system over a year to see what happens and how bothy visitors react to it.

The geotextile bag idea is actually rather complicated - according to the brochure, liquidised effluent needs a flocculating agent added to it to help the solids precipitate. We wouldn't be using water, but would the bags dry out anyway? We set up a simple trial using tins of sweet corn and baked beans -standard bothy fare - and watched these de-water to a dry mass in a few days.

What we proposed, then, to the National Trust Mar Lodge Estate and the Cairngorm National Park Authority was that the MBA add a simple structure to the south of Corrour bothy which would house an experimental toilet using the geo-textile de-watering bag system. A standard pedestal seat would be mounted on a raised floor and a bag attached underneath. When full, the bag would be left to de-water, and the pedestal moved to be positioned above a second bag.

When the second bag was full, the first would be detached and stored in a secure structure and a new bag fitted. The stored bags would be left to decompose over time and when safe, either buried in a suitable location or removed from the site.

After a lot of discussion between all concerned, applying for planning permission, and negotiating over health and safety issues, this proposal was accepted. Scotland Unlimited also gave a grant to support a maintenance programme that would monitor the toilet over a year's use. The maintenance would be undertaken by MBA personnel, who would monitor the toilet, change over the bags when necessary, and take samples for analysis.

Returning to the greatest challenge - people using the bothy - we have faith that visitors will recognise the work that has been invested in improving Corrour and will take responsibility themselves for its maintenance.

All of the work, reconstruction, and negotiations to date have been done entirely on a voluntary basis through the wish for Corrour to continue as a shelter for those who love wild and lonely places. If visitors are not able to rise to the challenge of looking after what is in fact their bothy, there is a high risk that the bothy will have to be demolished and removed, as have other shelters in the Cairngorms.

We ask all who visit Corrour take special care to look after what has been provided for them. This means not only making sure that any personal mess and rubbish are cleared up and removed from the site, but also any mess left by others is also cleaned up and removed. The toilet is not designed to take anything other than human excreta and toilet paper. Men are advised to urinate outside, well away from the bothy, to keep the liquid entering the toilet to a minimum. All rubbish, tins, bottles, food of whatever kind should be removed from the bothy and in no circumstances put down the toilet.

If there are serious problems that cannot be resolved, please contact the MBA at www.mountainbothies.org.uk, or leave a message (excuse the pun - ed.) or feedback at www.compostloos.org.uk, a website dedicated to the Corrour project.

Corrour Toilet Guts. This is the custom steel body with vent pipe to which the de-watering bag is attached.
Photo: John Cant