Alan Agace has a piece of paper he thinks may ensure the environmental survival of a threatened valley.

The document is a 20-year-old covenant guaranteeing Sheepcote Valley only be used for education, recreation and agriculture.

It could throw a legal spanner in the works for two of Southern Water's proposed eight sites for a new sewage treatment plant serving Brighton and Hove.

For many years, Sheepcote was the main rubbish site for Brighton, despite councillors promising it would have a greener future.

But in 1979, East Sussex County Council, then in charge of rubbish tipping, came up with plans to use some of the land for a rubbish transfer station.

A public inquiry was held into the proposed compulsory purchase order to buy the land from Brighton Council.

Mr Agace, 68, a member of the Friends of Sheepcote Valley and long-time resident of Swanborough Drive, gave evidence at the inquiry and the inquiry found against the order. A rubbish transfer station was ruled out.

When the latest plans for the valley were revealed in The Argus, Mr Agace, a bricklayer, rummaged in his attic to dig out the 38-page inspector's report.

Its conclusion reads: "For many years it has been a firm and much-publicised planning objective that once tipping had been completed and the land restored, the whole of Sheepcote Valley should be used for recreation, education and agriculture.

"For at least 21 years, the public has expected the whole of the valley, from the racecourse in the north to East Brighton Park to the south, would eventually not only be a pleasant open panorama but that it would be used for purposes that could cause no possible environmental detriment to the general public and residents in particular."

The inspector said people had bought houses there on that basis and added: "It is no wonder the local residents feel completely betrayed by those responsible for the safeguarding of their future environment."

The Friends of Sheepcote Valley campaign group will include the report in a growing dossier it will present to Southern Water.

The dossier also contains an ecology report on the valley's wildlife, hundreds of letters from the people of East Brighton and petitions organised by community groups.

Mr Agace said: "I campaigned for six years to get this landmark decision on the future of Sheepcote Valley and I am prepared to fight for another six years against a sewage works."

City open spaces councillor Heather James said: "We will have to take what was said then into consideration but it was a long time ago.

"My personal feeling is that Sheepcote would be the wrong place. The lower site is too small and the upper site is too visible."

A spokeswoman for Southern Water said: "Southern Water welcomes contributions during the public consultation period, which ends on February 10.

"The company must find a site for a new waste water treatment works to serve Brighton and Hove in order to meet The European Urban Waste Water Treatment Directive.

"Whichever site is chosen as the option for a planning application, the company will endeavour to replace any amenities removed during the construction process."

The other sites being considered are Black Rock and Kemp Town gasworks in Brighton, Ovingdean, Peacehaven, Brookside Farm, Newhaven, and North Quay, Newhaven.