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Figure 1: The South West Coastal Path as it passes the perimeter fence of the former Nancekuke facility ( Credit: Ceri Sansom)

Innocently passed by thousands of walkers each year as they traverse the South West Coastal path along the dramatic northern coastline of Cornwall, is the chain link fence marking the perimeter of RRH Portreath. A MOD sign warns of “dangerous cliffs and old mine workings”, while through the security fencing, walkers may spot the ‘golf ball’ like dome of the radar system and the long expanses of the runways. 

However, very few other clues remain to tell the true story of one of Cornwall’s most contaminated sites and its sinister history as a secret government base where an estimated 20 tons of deadly nerve gases, including Sarin, were produced covertly for over 20 years. 

Chosen for its ideal cliff-top location, the site was first established by the RAF in 1940 acting as an airbase and fighter command station involved in the defence of Britain during the Second World War. Following the end of the war, the benefit of the base’s remote location with only a sparse local population would make it the perfect choice for siting a new top-secret chemical weapons production facility. It was known as the Chemical Defence Establishment or CDE Nancekuke, taking its name from the small hamlet where the base was located. 

Figure 2: Pilot plant at CDE Nancekuke used to produce nerve agents (Credit: twitter/x user: @jon_agar)

Deadly Production

CDE Nancekuke was to become one of Britain’s premier centres for the research, development and manufacture of deadly nerve agents. This included the production of Sarin gas, a colourless, odourless liquid that was used as a chemical weapon due to its extreme potency as a nerve agent. Sarin was later outlawed by the Chemical Weapons Convention of 1993, of which the United Kingdom was a signatory. 

Approximately 20 tons of nerve agents, including Sarin, were covertly manufactured at the Site. To the alarm of the public at the time, the deadly chemicals were being transported by van using the local road network. During its operation, concerns were raised by the local communities, and even workers themselves, of the dangers posed by the facility and the material it produced.

However, under the Official Secrets Act, much of this remained hidden from the public for many years. Reportedly, stockpiles of the manufactured deadly chemical remained at the base until its eventual closure in the 1970s. 

CDE Nancekuke was able to operate under secrecy due to its relatively remote setting. The site, however, was also chosen for the other benefits the location offered, which were exploited leaving a legacy of one of Cornwall’s most contaminated sites. 

A Rich Mining History
Mining of Cornwall’s underground mineral riches is thought to have occurred across the county since the early Bronze Age around 4000 years ago, and peaking sometime in the 19th century when there were over 2000 known mines.

The commons of Nancekuke extend from Portreath in the south west to Porthtowan in the north east. In this area, bordering the high rugged cliffs, are records of a number of ancient mines, some of which were already described as ‘old works’ as early as 1753. Due to their age, the mining records are relatively poor and often incomplete, providing only a hint of the activity which took place below.

Early Ordnance Survey mapping conducted in the 1870-1880s depicts numerous waste tips and shafts across Nancekuke common and stretching along the clifftops. However, there are often no corresponding mine plans associated with the features to show the location of the underground or near-surface workings. The many small mines within this area were grouped or ‘consolidated’ to form Wheal Lushington Mine also known as  West Wheal Towan Mine.

This included Wheal Sally located in the northeast of RRH Portreath, which was the focus of activity during 1920-1925, under the name of Sally’s Bottom. Even during the relatively late reworking of these mines, records are sparse and the true extent of the mines underground remains a mystery. 

Figure 3: Excerpt of the 1888 OS Six-inch showing part of Nancekuke site with West Wheal Lushington and old shafts and quarries labeled to the north west, associated with Wheal Sally (Credit: Reproduced with the permission of the National Library of Scotland – )

A Convenient Disposal

It would be these numerous abandoned mine shafts dotted across the site, which would prove to be a tempting and convenient means of waste disposal both during and following the closure of the CDE Nancekuke. 

The release of a document titled “CDE TECHNICAL MEMORANDUM No 8. DATE: NOVEMBER 1980. CLOSURE OF CDE NANCEKUKE” under a Freedom of Information Request, provides an insight into the scale of waste dumping at the site. During CDE Nancekuke’s operation effluent and waste from the chemical manufacturer were reportedly disposed of in the abandoned mines, including within the open mine shafts of Wheal Sally.

Within the report, it is stated that no chemical warfare (CW) agents were present on the site at its time of decommission, noting that “CW agents were either incinerated or treated with decontaminate and disposed of as effluent harmless to marine life.” However, contained within appendix 10 additional information details an outfall from the site where effluent was discharged into a sea cave to disperse into the sea. 

While the report found no evidence that this effluent “…had any effect on the marine algae population in the vicinity.” in 1969 it was reported that hundreds of marine animals died around Nancekuke without any explanation. Locals raised concerns for many years regarding the safety of the site and the mystery surrounding the chemicals used and produced.

Figure 4: Sketch map of the effluent cave north of the Nancekuke taken from the appendices of the Closure of Nancekuke memo (Credit: CDE TECHNICAL MEMORANDUM No 8. DATE: NOVEMBER 1980. CLOSURE OF CDE NANCEKUKE )

The memo also details the dismantling of buildings and equipment during the CDE Nancekuke closure. The memo indicates that where possible, equipment was sold or repurposed. However materials that were considered contaminated, unsafe, or no buyer could be found, were buried on-site in multiple dumps – “When the previous use of an item was unknown the policy was to break it up and bury it in a deep quarry (dump “A”) on site, or in one of two mineshafts (D or E).”

A total of five known dumps were used for this purpose across the site to dispose of harmful or contaminated materials, which included:

With the exception of Dump B, formed of a land raise of up to 5m, it is possible that the quarries, pits and mine shafts were used for dumping waste during CDE Nancekuke operational period. The five dumps across the site have each been designated Contaminated Land under Part IIA of the Environmental Protection Act 1990. Only two other such sites have been recognised by Cornwall Council as contaminated land across all of Cornwall. As required under Part IIA, Cornwall Council must maintain its contaminated land register (CLR), which details the investigations to date and risk assessment relating to the five dumps at Nancekuke. 

Remediation Management

In the early 2000s Wheal Sally, or Sally’s Bottom Mine was subject to extensive investigation, underground inspections and subsequent remediation stabilising the mine and sealing it off to help prevent the escape of contamination. CCTV cameras used as part of the inspections were lowered into boreholes drilled targeting the historic shafts, showing that they had been at least partly filled with tightly packed plastic bags of waste. 

One of the major concerns was that waste or chemicals had migrated from the infilled shafts to the connecting mine drainage tunnel (known as an adit) below, following out at Sally’s Bottom Cove to the beach, providing a direct pathway for contamination to enter the sea. Due to the nature of the wastes and the mine, this required oversight by chemical warfare agent specialists at the Defence Science Technology Laboratory to allow the tunnel to be entered safely and possible chemical agents identified.

Fortunately, these inspections revealed that there was no notable Ministry of Defence waste within the adits which could be washed out to sea. Additionally, water sampling results indicated that some metals, particularly zinc, were elevated likely associated with the mineralisation, but no traces of chemical warfare agents, related contaminants or organic compounds were detected.

The site at Nancekuke remains under the ownership of the MOD and is subject to ongoing monitoring which is set to be undertaken until 2050. Each of the dumps is located within the military site, protecting them from potential disturbance, and sealing the contamination underground. 

It is not unusual for mines to be repurposed, sometimes for waste disposal, although rarely for something this potent. The contamination dumped within the mine shafts at the former CDE Nancekuke has been investigated and sealed to protect people and the environment. The five dumps across the Site are designated no build areas and are protected by their location within the heavily protected MOD site. 

Not a Place of Honour

The site represents an example of similar chemical and nuclear waste dumps that will leave a long lasting legacy for future generations. There is a long term project to consider how to communicate about this into the future and how to sign and identify it. The so-called “Not a place of Honour” identification is being considered as a way of attributing extreme risk sites with symbology so it is easier to interpret should records be lost in the mists of time. A site like Nancekuke could lend itself to this very easily.  

And while chemicals such as Sarin do not present with the same characteristics as nuclear waste, it represents a clear danger and ongoing management risk. There is a risk factor that its proximity to an eroding coastline may present significant transmission risks should the remediation become compromised by landslides in the future, accelerated by climate change.

In the shorter term this is clearly being managed, but maybe not forever.  Historical shafts and mining features continue to present both a ground stability and contamination risk as development continues.

Our Avista environmental reports provide the most comprehensive view of past mining activity from both coal with a fully inclusive CON29M, together with reporting on more than 60 other minerals. 

In addition to contaminated land, planning and infrastructure searches (essential for rapidly changing urban areas), Avista also looks into the future thanks to our unique ClimateIndex™ analysis module. This looks at the potential forward impact of climate change on a property-specific basis for a 5- and 30-year period. This helps your client understand the risks from flooding, subsidence and coastal erosion now, for a typical mortgage term and for within most re-sale periods. 

For more information on our expert support for mining and land contamination risk assessments email or call 01273 257 755. 

  8. Hobbs, SL 2013, ‘Assessing and managing the long-term risks and liabilities at a closed Cornish mine used for waste disposal’, in M Tibbett, AB Fourie & C Digby (eds), Mine Closure 2013: Proceedings of the Eighth International Seminar on Mine Closure, Australian Centre for Geomechanics, Cornwall, pp. 509-522,
  11. Hobbs, SL 2013, ‘Assessing and managing the long-term risks and liabilities at a closed Cornish mine used for waste disposal’, in M Tibbett, AB Fourie & C Digby (eds), Mine Closure 2013: Proceedings of the Eighth International Seminar on Mine Closure, Australian Centre for Geomechanics, Cornwall, pp. 509-522,