Tuna Hästberg Iron Mine, Sweden

The landing gear whirred and clunked into place beneath me as I looked out over countless islands and small white boats on the topaz-blue sea. I was about to make dives in the ancient iron mines I had first read about as a DAN intern in 2007. At last, here I was in Sweden. The country is dotted with flooded mines, but there is one in particular that has been modified to accommodate divers. Its passageways are littered with artifacts and are brimming with cold water offering endless visibility; a well-preserved window into the past. We have flooded mines in my home country of Australia, but none with such a rich history. At the airport in Stockholm my rental car was a station wagon with plenty of room for extra baggage. No satellite navigation, but a map in the driver's door was all I needed to locate Borlange, a few hours drive north towards the center of Sweden.
The long road to Tuna Hästberg
Every dive carries some level of inherent risk. The more complex a dive, the more risk must be accounted for in the planning and preparation. This particular site required technical training and specialized equipment to accommodate the enclosed environment and cold waters. Wearing 200 pounds of dive gear and utilizing a scooter to navigate a complex maze of tunnels at 100 feet in very cold water is not everyone's idea of fun, and it should not be considered without the proper training. I have been trained and hold the appropriate cave diving and decompression certifications for this dive environment.

In this case, I addressed my risk management in a number of ways. First, I thoroughly researched the site to gather as much information about the dive environment as possible. Then I contacted experienced cold water divers for advice about the thermal protection. After gathering the appropriate equipment, I conducted several pre-trip dives at my local quarry with my new under suit and dry gloves to become thoroughly familiar with them. When I began my exploration of the mine, I conducted an easy, low risk check-out dive for my first dive to make sure everyone on the dive team was on the same page. Our dives throughout the trip started simple and gradually increased in complexity.
Entering the mine

After driving through pine forests and gently rolling countryside, I arrived at my hotel to begin assembling my gear. The mine was near the village of Tuna Hästberg. The mine's history extends back to at least the 15th century and today its main shaft is on a 30-45 degree angle with excellent Scandinavian pine stairs descending into the black. A hoist trolley lowers and raises the dive gear next to the stairs. My research indicated the water temperature was around 38°F, which is colder than anything I'd dived before, and the passages I'd be visiting were at approximately 100 feet deep. I was expecting some short decompression obligation dives, meaning my thermal protection had to be up to the job.

For about two months prior to this trip, I dived every weekend in my local quarry, checking for pinhole leaks in my drysuit and sealing them up. I'd fitted dry gloves and ensured I'd gotten used to them and could still shut-down any valve in case of a freeze up. My regular Australian undergarments had been upgraded to a European set, which were warmer, but also thicker so I'd started wearing a weight belt again.

Finally after months of preparation, the morning arrived and I met the dive crew at the mine. We loaded the gear trolley in a light sprinkle of rain, sent it down 250 feet below the surface and walked down the stairs, helmets and headlamps on. Before diving, our hosts Daniel and Nicklas led us on a tour of the dry passages. Though it was toward the end of summer, waterfalls hung solid, ice on the floor crunched underfoot, and in one passage the walls were covered in frozen crystals which sparkled like diamonds in the light cast by our headlamps. In one particularly massive chamber, Nicklas asked us to turn off our lamps while Daniel lit a row of flaming torches high above us and a recording of a Scandinavian female vocalist filled the room with a mournful melody.

After the tour, it was time to dive. Everyone began to assemble sets of doubles and stages, get dressed and lower kits down to the floating dock about 10 feet below us. In the early days, Daniel and Nicklas used to crawl down here in the dark to make short exploratory dives. Now they're connected to the power grid and have established walkways to maneuver, fully equipped with lighting, a compressor, a blending room and even a heated lunchroom for warming up between dives.

As I set about running through my pre-dive checklist, "what if?" questions started popping into my head. What if my suit leaked? What if these tanks are lighter than usual and I lose buoyancy at the end of the dive? I'd come a long way for this, and as I finalized my preparations my nerves began to settle.

Daniel briefed us at the whiteboard. We were divided into two teams, each with a guide. The target we planned to visit during this check-out dive was an abandoned wagon in a room at 100 feet. The guides made us three new guys feel comfortable with the plan; they made it clear anyone could call the dive at any time. The plan was to stay within our no stop limits for EANx32; Nicklas lowered some oxygen to 15 feet as an added precaution. The platform fell silent as we each geared up and ran through our individual pre-dive checks. Then the moment arrived.
Referencing the cave
The water hit my face, I sucked in and then remembered to breathe evenly to avoid dropping the temperature in the first stage too much. My dry gloves were working alright, but my face was painfully cold, my lips especially. Tentatively I dipped my face in and out of the water until it became acclimated to the temperature. I flushed my mask a few times to get my eyes used to the cold, in case it flooded later on. We signaled each other, dropped to 15 feet, checked all was well and headed down a black, man-made passage 300 feet underground. After ten minutes or so, we reached a vertical shaft and waited for the least experienced cave diver to "place the jump," in other words to reel a short line from the line we were all following down to the line leading to the wagon. This is now fairly standard cave diving practice in many places. To avoid creating a web of lines we make one main line and then many side lines which are not connected, unless a team is visiting a side passage and puts in their own short connection, called a jump. I placed a personal marker on the line (called a "cookie") to indicate we were in the cave. This is done because if the two teams separated and my marker was still in place, it indicates the jump line back to the main line should not be reeled in.

We reached the wagon, a little wooden ore cart that Daniel said could still be rocked back and forth on its wheels even after all this time. I felt a sense of déjà vu, having studied photos of this exact place in articles and on the website. Heading back I removed my personal marker, the other team reeled in the jump line, we made our safety stops and surfaced. Daniel asked if I'd like to see the little house at 60 feet along a passage in the opposite direction. I knew this was another opportunity to "reference the cave" (find my way around). Compasses don't work in this mine, but the main geological fault that was mined for hundreds of years lay on a fairly uniform angle; it is possible to navigate using natural references such as depth and cave topography. It just requires time in the water to develop familiarity. I resubmerged and we set off again. The little house was constructed to serve as a shelter when dynamiting for ore. It looked cozy, not much bigger than a phone booth from the front; I imagined four miners huddled together for warmth inside the tiny structure. It is humbling to observe such a well-preserved window into the past.

After removing my wet gear, I headed to the heated room for some lunch. My companions chatted in a mixture of languages as we shared tales of our experiences. I described our caves in the Australian desert and Nicklas told me about the 375-foot dives he and his mates had made here in the mine, even fulfilling some of their decompression obligation in a natural room filled with air at 15 feet.

After lunch I dived with Nicklas. When we reached a depth of 110 feet Nicklas led me to the Ostra/Västra sign and then on to the power room filled with switches and dials. Workmen's gloves lay here and there, a reminder that when they had laid down their tools at the end of their last shift they had fully expected to return to work. The mine had flooded while they were away and after considering the costs of pumping it dry and electrical repairs, the mine was abandoned. Upon our return to the dive platform we had earned 15 minutes of decompression each; as an added safety precaution, we used 100 percent oxygen for half of that obligation.

The gear remained underground overnight, torches on charge and drysuits hanging in the relatively warm compressor room. The following day, my last at this mine, Daniel arranged a special treat for me: the loan of a shiny new long-body scooter. Four of us made our way to the main chamber and dropped down through a passage to around 60 feet, where I placed a cookie onto the line at a T-intersection, at the side we had just come from. We returned to the main chamber, crossed it and entered the "Secret Passage," which circles around to the passage where I had just left my cookie. If my cookie was not on the line when we reached the T at the end of this mysterious passage, we would retrace our route and exit the way we'd come. To do this safely we would need to monitor our gas to make sure we had sufficient supplies to retrace our steps, if needed, accounting for the possibility of donating gas to a buddy in case of a failure. In practical terms this meant we would have to reach the cookie before any of us used more than one third of his available gas, a procedure known in cave diving as the "Rule of Thirds." Because of the depth and time we expected the circuit to take, we each wore an extra tank under our left arm, known as a "stage." With a set of doubles on my back, a stage under my arm, three sets of regulators, three torches and a big scooter, I was wearing about 200 lbs of dive gear, but I was accustomed to wearing this amount of gear because of the preparation dives I made back home.

Traveling in a single-file line we flew along passages careful to avoid entanglement hazards, such as hanging cables and the guide line. We passed through the mine's massive wooden doors and followed the ore cart rails. It was marvelous fun, a real adventure. After completing the circuit and collecting my cookie we clipped our scooters to the line and ascended into the habitat, a room carved into the stone and now furnished with a wide pine bench for divers to sit out of the cold water during long decompressions. Then, we resubmerged heading back to the entry lake to ascend the final time from the flooded mines of the past.

For more information about the mine at Tuna Hästberg, including a gallery of cave-diving photographs, visit: http://www.aventyrsgruvan.se/gallery.asp
About the Author
Peter Buzzacott was a DAN intern in 2007 and a former DAN instructor. He researched post-course diving injuries among recreational divers for a Master of Public Health Degree and earned a PhD from the University of Western Australia researching risk factors for recreational diving injuries.