Plans have been revealed to extend a quarry to extract 500,000 tonnes of sand and gravel and restore part of a chalk stream.

Middleton Aggregates has applied to Norfolk County Council to excavate 28 acres of land to the east of its existing Pentney Quarry, near King's Lynn.

West Norfolk council, which was consulted over the proposals says it has no objections.

A planning statement says work will begin once reserves have been exhausted within the current working area of its existing quarry.

Once it has been worked, which the company expects to take eight years, the extension will then be restored progressively to a mixture of open water, woodland, grassland and reedbed.

Areas around Pentney where sand and gravel have previously been extracted have been turned into lakes for leisure and wildlife such as Pentney Lakes and Nar Vallet Fisheries.

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The statement says the latest work at Pentney will be accompanied by improvements to a mile-long stretch of the River Nar, which runs to the south of the site.

These will involve work on the river channel and its banks "aimed at improving the appearance and biodiversity potential of the river".

Middleton says reserves of aggregates at the existing quarry are now being depleted and are expected to be exhausted by 2028.

It says of its 50-strong workforce, two full and six part-time staff who live locally depend on the quarry and were the extension not approved it is "probable" some or all would lose their jobs.

The statement says the quarry produces high-quality soft sand used in brick-laying mortar, of which there is a national shortage and sharp sand used for making concrete.

Norfolk County Council said a date has not yet been set for a decision on the proposals.