They say that where there's muck there's brass. That could come true literally before too long where the economy of part of the Fens is concerned.

Tug boats set out from Ely's waterfront yesterday on a dry run for what could soon become a regular voyage.

The mini flotilla is expected to arrive in King's Lynn by this evening.

Anglian Water is investigating whether barges could be used instead of tanker lorries to transport sewage sludge from Ely to its treatment works at Clenchwarton, near King's Lynn.

As the tugs set off towing a large pontoon, the company said it planned to use two 200-tonne barges, with each trip saving 16 lorry movements.

Similar vessels would be expected to operate on the rivers Nene and Witham, carrying sludge from Wisbech and Boston to Lynn via The Wash.

Ely Marina owner Jeremy Tyrell, who supplied the tugs used in yesterday's trial run, said: 'It's a wonderful thing for the river. If we could get more commercial traffic, it would bring money into the river and bring a lot of lorries off the road.'

Mr Tyrell said the movement of heavy craft would help clear silt from the tidal river downstream of Denver, while lock openings needed to allow craft to transfer between the Ten Mile and tidal Ouse would help migrating elvers on their way upriver.

Anglian Water spokesman Ciaran Nelson said: 'Our King's Lynn Sewage Treatment Works currently receives up to 60 lorry movements per day. The combined effect of this barge combination working on the River Ouse with that of a coastal barge working between our sites near Wisbech and Boston to our King's Lynn site will be to reduce lorry movements to approximately 10 per day.

'The coastal barge will have a capacity of 1,500 tonnes (60 lorry loads) per trip. We're focusing on the barges on the river at the moment, but the coastal barge trial may follow, as early indications look positive.'

Mr Nelson said if it went ahead, the barge scheme would replace 660,000km of lorry journeys each year. River users will be consulted over the plans.

The trial barge will be passing through Denver Lock this afternoon.