The final phase of a flagship development of riverside flats near Norwich City Football Club has sparked controversy, after two of Norwich's biggest companies raised concerns the plans could impact on their business.

The owners of the Colman's and Robinsons brands described proposals for the last 174 flats at what is known as Riverside Heights as 'one of the most significant threats to their operation' in more than 150 years in Norwich.

Britvic and Unilever, which own the brands which produce the iconic Colman's mustard and the popular fruit drinks, are concerned over the impact of the building of the flats on the production of their products at the Carrow Works factories across the river.

Letters sent to planning officers and councillors at City Hall in the summer by Norwich-based chartered surveyors and property development consultants Harvey & Co on behalf of Britvic and Unilever, revealed how they had three sets of concerns about the plans for the flats, submitted by Taylor Wimpey.

One concern was that dust from the redevelopment could be blown over to Carrow Works, potentially contaminating products, which would damage the brand if it become public knowledge.

A second was that it was vital that a water aquifer the companies use needs to remain uncontaminated, while the third was the fear that people moving into the flats who subsequently complain about noise from the factories could force restrictions to be placed on the activities of the companies.

David Harvey, from Harvey & Co, wrote in a letter that it was 'vitally important for both companies that the viability of their business at Carrow Works is not jeopardised by developments on surrounding sites and that they are able to continue to attract investment from their parent companies to a site that can operate freely, without restrictions.'

He wrote: 'Without appropriate measures being taken at this stage, our clients believe the inevitable outcome is that residents will at some stage in the future object to the 24 hour operations at Carrow Works.

'Both companies operate in a highly competitive global market. Significant costs incurred to modify operations at Carrow could put the companies at a serious commercial disadvantage.

'Having been objection free for over 150 years, both Britvic and Unilever perceive this to be one of the most significant threats to their operation in that time.'

He said it was essential measures be taken to ensure the design, specification and siting of the buildings meant that any noise, odour or light from the factories could not be deemed to be unacceptable and future complaints not upheld.

The Broads Authority is also unhappy about the design of the flats, which would be built next to the existing blocks of flats, saying the scale, bulk and form are 'inappropriate to the location', while concerns were also raised by the ecology and natural areas officer that the value of the area for wildlife would be reduced.

The proposals will come before members of Norwich City Council's planning committee this week and officers are recommending approval, albeit with a string of conditions attached.

The conditions include groundwater protection measures, care over dust created during construction and that measures be taken by the developers - such as acoustic glazing to windows and ventilators so windows and doors can remain shut - to minimise the exposure of people living in the flats to noise from the factories.

Mr Harvey signalled that could prove acceptable with Britvic and Unilever. He said: 'We have been in negotiations with the officers at City Hall and they have taken measures to ensure the concerns are allayed.'

Richard Abbott, who is acting as agent for the developers Taylor Wimpey, said he was hopeful the scheme would win approval when it is discussed on Thursday.

He said: 'We have listened to everyone's concerns and addressed them where we can. The concerns the Environment Agency had about flooding have been pulled as we addressed that.

'The scheme is a rationalisation of what was originally proposed so in effect the scheme has been reduced somewhat. 'The room for landscaping space has been improved somewhat, with we think will bring benefits.'

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