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Dry run Blue Circle has already spent £10M promoting its plans for a new Green Belt cement works in the south east of England. Dave Parker reports.

From Blue Circle's point of view, Holborough, near Snodland in Kent, would be the ideal site for a new 1.4Mt per annum greenfield cement works. The company opened its first works there more than 70 years ago - just one of the 20 or more cement works that have been built in the Medway valley since abundant supplies of raw materials began to be exploited in the late 19th Century. The original Holborough works was closed and demolished in 1973, but planning consent to extract chalk and clay remains, and reserves there are put at 35 years.

Blue Circle makes no secret of the fact that its need for a new works in the south east is pressing. The company's 28 year old Northfleet works on the Thames has only six or seven years of raw material reserves remaining. Cement demand in the region is projected to rise more than 10% by 2020. Environmental pressures, especially on noise and emissions, are likely to get much tighter in the future, while competition from imports is an ever-present threat.

'Logistically, the ideal location would be Blackheath [London], in the very centre of the area we supply,' says new works project director Jack Davies. 'But at Holborough we would still be well located, with 50% of our customers within a one hour radius, and 90% within two.'

In fact, the chosen site lies between the M2 and the M20, with the Rochester to Maidstone main line running just the other side of the A228. Another advantage is its relationship to the villages nearby, Davies says.

'It is possible to create a minimum 500m wide green border around the site and any houses in the vicinity, and to build the works at a level some 10m below general ground levels in the area.

'This will really minimise visual intrusion on the landscape, and make it easier for us to keep noise levels down.'

Unfortunately for Blue Circle, this ideal site is just across the road from the original Holborough site, and is officially within the Green Belt. Ironically, although the company owns several sites in the area which are outside the Green Belt, it says that works built on any of these would be much closer to residential areas, and much harder to screen.

Davies says two other sites were given serious consideration, as was an upgrade of Northfleet, but all these options had environmental and economic drawbacks. Convinced of their case, the new works team began to promote Holborough as the site for what was soon dubbed the Medway works - in recognition of the valley's cement producing heritage, Blue Circle says.

An 'open consultation approach' was adopted, and a public exhibition of the proposals was mounted in 1996. Local response was not exactly encouraging, Davies admits. 'At best, we changed some people from being positively hostile to being neutral - but many remained hostile.'

He goes on: 'The problem was that many locals remembered the old works in the valley, and the dust and the noise and the smell it produced. And there were worries about extra traffic, and the visual impact on the area.'

It was not quite a case of back to the drawing board. Blue Circle knew that much local concern was related to the old wet process works that had been traditional in the area, and that the planned new dry process facility would be inherently less offensive. This would be pushing cement manufacturing technology to its limit, Davies points out, as the wet process was specifically developed to use soft materials like the Medway Valley chalks and clays.

'The dry process is more energy efficient, but is usually associated with harder limestone and shales,' he says. 'This is an opportunity for us to demonstrate our expertise, using the dry process with wet process materials.'

Other objections were harder to accommodate. Chalk could be won on the site, but the clay source was nearly 2km away near Snodland village. In the old days, clay had travelled from there to the original Holborough works by an aerial cableway of ill repute.

Eventually, concluding there was no universally acceptable way of transporting clay to the new site, Blue Circle made the decision to switch to the chalk marl beneath the chalk measures on the site.

The marl is also below the water table. 'However, there are enormous environmental and operational benefits in using the marl,' Davies insists. 'And the lake we create over the life of the works will be landscaped to create a major wild life habitat.'

It will take a couple of years of quarrying to create the space and depth needed to house the giant bucket wheel excavator that will extract the marl. Until then, Medway will depend on imported sand and pulverised fuel ash for its source of silicates.

Iron oxide will be needed as a flux - unless current proposals to burn chipped tyres, as well as coal and petroleum coke, go ahead. Then, the necessary iron will be supplied by the steel belts in the tyres.

Current design for the works proper is a highly efficient pre-calciner type with extensive heat recycling. Blended and milled raw materials will first be pre-heated by waste hot air from the kiln before passing into the calciner.

Here, around 60% of the total fuel used will be burned to raise the temperature of the materials to 900C before they enter the rotary kiln proper, where clinkerisation will take place at around 1,450C.

This final stage will be boosted by hot air from the clinker coolers. Before any exhaust gases can leave the chimney they will have to pass through a series of bag filters, just one of the many dust control measures planned for the works.

'The bag filters alone will cost £4.5M,' Davies says. 'They will take care of the high level emissions. Total enclosure of the rest of the works will take care of anything at low level.'

Artist's impressions of how the Medway works might look show an unusually sleek installation. No accident this, as Blue Circle took the (probably) unprecedented step of calling in world-famous architect Terry Farrell to give the basic design a makeover.

Some 30,000 trees will be planted around the site, while topsoil removed during the quarrying operations will be stored and managed for up to 35 years, ready for the final landscaping after the works is demolished.

Blue Circle has also included the possibility of a rail link to the adjacent main line in its proposals, although Davies says that rail deliveries will not be a practical proposition in these days of bespoke cements until piggy-back road/rail delivery systems are perfected.

Until then, Blue Circle has given an undertaking that 98% of the lorries leaving the plant will turn south down the dual carriageway section of the A228 towards the M20.

Most of the company's multi-million pound investment in the project to date has gone on a detailed and exhaustive environmental impact statement. Calculations have been made as to the likely effects on local air quality and noise levels as well as traffic flows.

Visitors to the current exhibition in Holborough can see computer-generated images of how the works would appear from hundreds of different local vantage points. So far, Davies reports, the company has distributed 150 sets of the three volume, 180,000 word statements, each of which costs it £300.

Although Blue Circle says it is confident that it will get planning permission for its preferred Holborough site, and that the new works will be open by 2002, it is aware it could face even more restrictions - on air quality standards, for example, or a requirement that a certain percentage of output is carried by rail.

The company originally hoped to open Medway in 2001, so 12 months have been lost already.

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