Construction projects are often faced with unusual challenges, but it can't be often that a team has been charged with adapting designs to account for the unknown forces of the universe.
Such unusual variables are influencing the design of the water treatment system for the pounds 14M Bath Spa, a millennium project to refurbish the city's ancient hot water spas and house them in a new complex designed by Nicholas Grimshaw & Partners. Bath has been famous since Roman times for its hot springs and for the treatment of rheumatism and other ailments, and it is the only medicinal spa resort in the UK.
The hot spring waters rise in three spas: the Cross Bath, Hetling Springs and the King's Springs, and archaeological evidence suggests that the Cross Bath spa was in use as far back as the Iron Age. The Romans later dedicated the spa to the goddess Sulis Minerva and Aescalapius, son of Apollo and god of healing.
A long and illustrious history was interrupted in 1977 when a girl died shortly after bathing in one of the hot pools. Tests later revealed that the water had become contaminated by amoebae, Naegleria flowleri, which can transmit bacterial meningitis. The disease is invariably fatal and the council immediately shut down most of the complex until a solution could be devised.
It is thought the amoebae is being picked up as the water flows from the limestone aquifer up to the surface through overlying mud.
'The important message here is that the springs themselves are uncontaminated - it is the passage of the water that contaminates it,' says Arup Environmental associate Michael Bull.
Arup's project brief is to come up with an effective water treatment regime for the spa. Extensive consultation has been carried out, as the springs are protected by an Act of Parliament, the Bath Act. Accordingly, a panel of experts and local representatives was assembled last year to scrutinise suitable water treatment solutions.
The membership includes Dr Simon Kilvington, renowned for his research work on fowleri and methods of detection, and Geoff Kellaway, a leading authority on the hydrogeology of natural springs. Other bodies represented include the Environment Agency, the city's chief environmental officer, the architect and an organisation called the Springs Foundation.
The foundation's remit is to protect the character, tradition, and heritage of Bath's hot springs, and to inform and educate the public. It works with the full co-operation of Bath City Council and won approval to reopen the Cross Bath to non-bathing visitors in 1991. Head of the foundation is Margaret Stewart.
There is an interesting history to Stewart's arrival at the foundation. She was bitten by a poisonous snake on a trip to Australia and has had strange dreams ever since, glimpses of what seems to be a Romano-Celtic past merging with present day events in a place she recognised as Bath, her birthplace. The dreams continued as she travelled on to Malaysia and Nepal, where she encountered poltergeists and psychics with the same message to impart: return home to your destiny.
Stewart returned to Bath in 1975 and the dreams began again. As she was walking past the Roman Baths museum one day, a voice in her head told her there was a job waiting for her as a guide. She got the job, and developed her talk to include descriptions of ancient Celtic ceremonies that may have been held at the spring, capturing the imagination of delighted visitors.
When plans were drawn up in 1979 to cap the Cross Bath spring and pump in water from the King's Springs, Stewart objected and negotiated successfully with the council to secure the tenancy of the Cross Bath and ready it for reopening to the public. As a representative on the project's consultative body, Stewart says she is there to carry out the directions of the springs themselves.
'Her belief is that there is spirituality associated with it and she believes it has alternative healing powers,' says Bull. 'The treatment brief was minimum intervention and the Spring Found- ation was very keen that it should be seen coming out of the ground untouched. I've no idea why they have such influence, but they are taken very seriously. They have come up with genuine ideas that we've had to test against public health criteria. Margaret is guided by her dreams, so we have had moving criteria,' he adds.
Arup is likely to recommend lining the boreholes and the deployment of an ozone and chlorine water treatment system for the springs, although the foundation is holding out for copper and silver ion treatment, which it insists would be a more minimalist solution.
Bull's case is that ozone and chlorine have established track records, whereas the preferred method of the foundation is less proven.
The tender for the water treatment is likely to be out by the end of the year. Arup is working on the detailed requirements of a monitoring system for the spa. 'It is recognised that public and client confidence will depend on the monitoring system,' says Bull. And the confidence of the springs themselves, it seems.