On Friday 7th July 2023 members of the archives team, both staff and volunteers, from Central Library visited DeepStore.
DeepStore is part of a working rock salt mine that doubles as an offsite archival storage facility and it is here that a lot of the collections of Manchester Archives are stored. This is generally more obscure items that aren’t requested as often as well as items that have been digitised such as our local images collection. Having this additional storage space helps us to continue expanding our collections to ensure the history of Manchester is preserved for present and future generations.

We headed there with the same basic knowledge: It is a salt mine, used to store records of historical importance and it includes some material from Manchester. A lot of us were familiar with ordering and receiving deliveries from DeepStore but we had no idea about the process of storing and retrieving documents from the mine. So, what happens before the items reach us? We went to DeepStore to find out:

On a lovely sunny day in July, we were welcomed by DeepStore staff and given an introductory session over a lovely cup of coffee. We heard about the history of the rock salt mine, why it was formed in Cheshire, what it’s primary function is and how it came to be a storage facility.
This is what we learned:
DeepStore is located in the Cheshire town of Winsford, about an hour’s drive from Manchester City Centre, within ‘The Winsford Rock Salt Mine’, the U.K’s largest and oldest working mine. The history of the mine began in around 1844 and today is around 1400 acres in size. The mine supplies the whole of the UK with natural rock salt to keep the roads safe from ice and snow during the winter. A task that needs to be prepared for all year round – with most of the mining completed during the summer.
We were shown images of the Continuous Mining Machine used to cut rock salt away from the mine face (like something you would see in the Thunderbirds or Doctor Who) which created a funky pattern on the walls a bit like ‘claw’ marks.


These machines are powered by electric and programmed to leave enough salt in place to form pillars, responsible for keeping the mine standing, stronger than any other replacement that could have been put there instead.
It sounds strange then that some of the most important historical, evidential records are stored within a mine – when long tunnels, dangerous conditions, a dirty environment and canaries come to mind!
However, the salt mines actually provide the perfect natural storage conditions for archival records. Lying around 150 meters underground the spaces that remain from the mining process have been innovatively used in this way since 1998 and as rock salt is mined every year this storage space only continues to grow.
Before heading into the mine we were told about the safety procedures, highlighting the risks of working in a mine but our friendly tour guides consistently put us at ease about our visit. They then helped us to put on our safety equipment:
- High Vis Jacket
- Belt fitted with emergency kit containing breathing apparatus
- Goggles
- Hard hat with lamp
We really felt the part:

We headed outside in the heat walking down a path next to a main road all kitted out and one thing I will mention now is the level of security they have there. Fort Knox comes to mind.

We were guided to the lift (the safer of two options the other being a shaft lift with a rope, platform, total darkness and the taste of salt) which took us 150m down, taking around 62 seconds and making our ears pop.

Coming out of the lift was another world experience, Indiana Jones and The Temple of Doom was on all of our minds at that point. We were led to a mini bus named the ‘mine tour bus’, DeepStore would give the minotaur’s maze a run for it’s money – I would not fancy navigating myself solo down there.

We were driven around the mines to different sections. We had the headlights from the bus but other than that it was complete darkness and was possibly the closest feeling to what it would be like on Mars. It was incredible to see the vastness of the mine, the fact that we could drive in a car just like on a normal road to see the different parts of the mine. We probably only covered a really small percentage in around 20 minutes.

As part of the tour we were then taken to our storage unit, again highly secure. Walking into that unit an instant difference in the environment was felt by all.

Naturally kept at a constant temperature of 14-15 degrees and a relative humidity of around 55% no matter what the weather is doing outside with minimal energy intervention. It was rather pleasant on such a warm day and the purest air you’ll ever experience!

Held on two levels, it was fun to see how the boxes are stored, wandering around the space to spot Manchester Archive collections, which of course we did. Our collections took up around 20% of the storage unit and it was great to see how these would have been retrieved and kept track of using digital barcode scanners on both the shelf and box.

We could have spent ages in the storage unit, entertaining ourselves by estimating how long it would take us to go through all of the boxes in that one unit alone and wondering what treasures lay there.

Sadly, the time in the unit came to an end and after a group photograph in the mine we headed back to the lift in the mini bus.

It was then back up 150m to reality after pretending we had left this world and entered another. On the way out of the mine we were struck by children playing on a park right above the salt mines oblivious to the storage below them and us.

Overall, the experience was absolutely amazing, there was such a relaxed, fun atmosphere for something that could be considered rather dangerous. The tour was really tailored around our institution and our questions answered with no trouble at all. I definitely came back with a better understanding of DeepStore and what it’s all about.
I had an amazing time visiting DeepStore for the first time. It was a really enjoyable and interesting experience, tailored to the items stored for Manchester.
The staff were very knowledgeable, answered all our questions and made us feel safe and comfortable going down the mine.
I hadn’t realised how vast the storage was there and it was great to see the other side of the process which is really useful for my role in archives.
I would definitely recommend to my colleagues!
Siobhan O’Connor
Thank you very much to DeepStore for having us and providing such a fascinating, enjoyable tour!