Neumann's Mine

Overview

A long-abandoned Northwich rock-salt mine whose roof collapse -- most commonly dated to 1873, though sources vary -- created Neumann's Flash, and which lay flooded and derelict beneath the town until a £28 million stabilisation programme infilled it between 2004 and 2007.

History

Neumann's Mine was one of the many rock-salt mines worked beneath Northwich and neighbouring Marston during the 19th century, in the era before solution mining by pumped brine extraction made the older dry-mining method obsolete. Sources differ on the exact date of its collapse -- most commonly given as 1873, though 1877 also appears -- when the breccia roof above the abandoned dry workings disintegrated after fresh water leaked down from the surface and dissolved the supporting rock salt; the resulting subsidence created Neumann's Flash, a lake still visible near Marston today and now valued as a wildlife habitat. This was a smaller, earlier instance of the same failure mode that would end all of Northwich's rock-salt mining in 1928, when the Adelaide Mine -- the last still working -- flooded for good. Neumann's Mine itself remained abandoned and flooded with brine roughly 90 metres below ground until 2004-07, when it was one of four mines (with Baron's Quay, Witton Bank/Hall and Penny's Lane) infilled in a £28 million, then world-record-scale stabilisation programme -- removing millions of litres of brine and replacing it with a mixture of pulverised fuel ash, cement and salt -- undertaken specifically to allow safe redevelopment of Northwich town centre above it.

Workings

Worked as a dry rock-salt mine in the 19th century; its collapsed void was later infilled with pulverised fuel ash, cement and salt during the 2004-07 stabilisation programme.

Closure

No reliable specific closing date has been located, distinct from the mine's own roof collapse (c.1873, sources vary) which is the event actually documented.

What remains

Permanently infilled with a pulverised fuel ash, cement and salt mixture between 2004 and 2007, as part of a four-mine, £28 million programme to stabilise Northwich town centre above it; the surface collapse it caused survives as Neumann's Flash, now a wildlife habitat.

Neumann's Flash, the subsidence lake formed by the mine's own roof collapse.

Abandoned workings can be dangerous — unstable ground, uncapped shafts, flooding and bad air are common even where a site looks safe from the surface. This entry describes history and general location only; it is not an access guide.

Recorded claims

Individual factual claims, each attached to the source(s) that support it below. Where sources disagree, both are kept.

• Neumann's Mine's roof collapsed -- most commonly dated to 1873, though other sources give 1877 -- creating Neumann's Flash; this is distinct from the 1880 'Great Subsidence' that created the separate, nearby Ashton's Flash. (disputed) ¹
• Neumann's Mine was one of four abandoned Northwich salt mines (with Baron's Quay, Witton Bank/Hall and Penny's Lane) infilled in a 2004-07, £28 million stabilisation programme, replacing brine at around 90 metres depth with pulverised fuel ash, cement and salt. ²

Photographs & further reading

This page doesn't try to reproduce everything — these are the best original sources found for this mine.

Images

Sources

1. (secondary) Neumann's Flash (geocaching/local history summary) — Atlas Obscura
2. (secondary) Northwich Stabilisation Project — Northwich Townscape Heritage Project

Record created: 1 September 2026 · Last researched: 1 September 2026