Olwolgin Cave Revisited

Olwolgin Roots
Olwolgin Roots — Photograph by Richard Harris

By PAUL HOSIE CEGWA

On 6th October 2011, a remarkable thing happened when I decided to revisit a muddy pool of water I had last looked at almost ten years before.

The pool was in the entrance chamber of Olwolgin Cave, Roe Plains, Western Australia, where 2700 m of cave diving passages had been explored and mapped since it was first dived in 2002 by me and Andy Nelson (CEGWA). While all the diving and exploration was being done from the ‘main’ (north-east = upstream) pool, the ‘other’ (south-west) pool had been ignored.

Olwolgin Downstream map 1
Olwolgin Downstream map 1

At the bottom of the ‘other’ pool, an awkward restriction was negotiated which led to a further 80 m of silty and reasonably small cave-diving passage.

Later that same afternoon, with full 7-litre cylinders and reels of knotted guideline, my primary dive buddy, Alan Polini (CEGWA) and I extended the new line straight into large phreatic conduit for several hundred metres with no end in sight. Turning on our thirds, we left an exploration reel tied off to the top of a large rock in the middle of a big tunnel.

Alan Polini (left) and Paul Hosie after their dive on October 7 2011. Ken Smith (left) and Brian Kakuk after their dive on October 7,2011
From Left: Alan Polini and Paul Hosie, and Ken Smith and Brian Kakuk after their dives on October 7, 2011

While surveying back out of the cave, several substantial side passages to the south were noted. There was disbelief around the campfire that night as Alan and I excitedly relayed our discoveries to the rest of the group. Sweet dreams indeed that night, and many more since.

Exploration in Earnest

This discovery was made at the end of a Roe Plains sightseeing trip with Brian Kakuk (Bahamas), Ken Smith, Richard ‘Harry’ Harris and Grant Pearce (all CEGSA).

As Alan and I had to drive back to Perth the following day, they prepared for one more dive in the new cave, but only after Brian and Ken had dived next to extend the line, and more importantly, retrieve Ken’s reel still in the cave.

The next morning, Brian and Ken explored several hundred metres of the main conduit (A Tunnel) and when they turned around on their thirds, Ken reported, ‘I was so overwhelmed by what we had just done that I was shaking with excitement, so much so that I couldn’t hold my pencil steady enough to write down the survey data, so Brian had to do it for me.’

As soon as Brian and Ken were clear of the water and it was obvious that extending the main conduit would require stage bottles, Alan and I headed in, laying over 400 m of line in side passages they had noted that were to become the C and D Tunnels.

A gas failure (free flowing 2nd stage) experienced by me at the furthest penetration of the C Tunnel (600 m) during this dive meant that no survey data were collected.

While Alan and I drove back to Perth, Harry and Grant extended the main tunnel using stage bottles to a penetration of over 800 m with the passage continuing, although it had reduced down to a much smaller, side-mount-only sized tunnel.

Ag’s Dreamtime

Before the rest of the group headed for home, Brian Kakuk was to make a sensational discovery while checking side tunnels at a penetration distance of 400-500 m.

After pushing through a small, non-obvious side tunnel for 20 m or so, the passage opened into a tunnel of generous proportions: 10-20 m wide and 3-5m high. This stunning cave-diving passage continued for almost 200 m before Brian had to turn on his thirds, where he tied off on a rock in the middle of a large, continuing passage.

On Brian’s suggestion and with the approval of her family, the passage was named after Australian cave diver Agnes Milowka, who had tragically died in a cave diving accident earlier that year.

Brian had this to say shortly after his discovery: 'I was hoping to maybe name that big passage Ag’s Dreamtime Tunnel, or something along those lines. I was thinking about Ag while I was swimming down that borehole, wishing she was showing it to me.'

And so it was that during three days of diving in early October 2011 over 1400 m of diving passages were explored and surveyed following the initial discovery.

There were three main leads, each continuing in parallel passages to the south-west with penetrations of 600 m (A), 800 m (B) and 550 m (C).

It was realised from the start that this was potentially a very large and complex cave system and therefore I established strict requirements for surveying and station numbering by the exploration teams, which is why I am referred to by some as ‘Sergeant Major Survey.’ Following the initial exploration hiatus, the passages were labelled according to their potential for continuation.

CEGWA Crew Raid

It took little encouragement for a return trip (‘The Raid’) to be organised by a small crew of keen CEGWA cavers and cave divers for a four-day long weekend in late October 2011.

Kim Halliday and Craig Challen paired up as a dive team with us, possibly over-enthusiastic with our rebreathers and scooters ready to explore caverns measureless to man.

The four divers were brilliantly supported by Christie Allen, Mark Brown and Jeff Gibson; they looked after everything around the camp and the cave so that the divers could focus on the cave diving.

Given the zero visibility and awkwardness of the first 30 m of diving through the entrance restrictions, a thick rope donated by Craig was fixed in place by tent pegs and weights, thus improving the situation massively.

The next piece of infrastructure to be put in place was a staging area, which was brilliantly set up by Alan 80 m into the cave. The staging area consists of a rope fixed horizontally to the side wall with several hanging lines, each having several D-rings on it to clip off scooters, stage bottles, rebreathers, etc.

Owing to a few equipment problems and the fact that Ag’s Dreamtime Tunnel shut down a further 70 m beyond Brian Kakuk’s tie off, only 600 m of passage were explored and surveyed on this Raid trip, but there were still a couple of leads at the end and many side passages marked for exploration.

Last dive discovery

On the last dive of this trip, a significant discovery was made at the end of the B Tunnel by Alan and me — The Sanctum, an 80 m long, 20 m wide, 2m high room/passage which had further leads to explore but was now over 900 m from the entrance and only accessible with sidemounts.

The next visit was during Easter 2012 involving Alan Polini, Grant Pearce, Chris Edwards (CDAA), Ken Smith, Liz Rogers (VSA) and me.

A significant event occurred early during the course of our diving when something shifted in the entrance restriction whilst four of the divers were in the cave. Owing to the zero visibility conditions we couldn’t be 100 per cent sure what had happened, but we believe the Letterbox rock (a big chunk of several hundred kilos) had shifted into a new position.

This shook us up a bit and stopped us diving for a few days until we were confident that the situation was stable and it was safe again to enter.

Olwolgin cave.  Liz Rogers photograph
Olwolgin cave. Liz Rogers photograph

We added only 700 m to the survey on this trip, bringing the total Downstream passage length to 2700 m. The most significant discovery was made by Grant and Chris when they extended the B Tunnel line to the south-west from The Sanctum and entered an enormous room which proved to be 130 m long, 30 m wide, 3m high with a completely flat roof at -4m.

Subsequent visits have shown that this remarkable room can be accessed from five different passages around its perimeter, hence the name Grand Central.

Cave Diving Conservation

I have written several articles and given presentations to the Australian caving and cave diving communities regarding the uniquely fragile features found within the Roe Plains caves.

The basis of this claim is that the most fragile features are organically based, rather than mineral or crystalline as found in other cave systems.

Whereas in dry caves it is the speleothems that warrant the greatest conservation and protection efforts, in these underwater caves it is bacterial colonies, threadlike tree roots and tree tap roots that predominate.

These features are very spectacular, with some of the tree roots hanging in drapes up to five metres long. They are incredibly fragile because they are decaying — rotting and breaking down — and this makes them highly susceptible to damage from divers’ exhaust air bubbles, fin kicks or body movements.

Olwolgin Downstream map 2
Olwolgin Downstream map 2

It is fortunate that the exploration of Olwolgin Downstream has been done following ten years of exploring and mapping of the Roe Plains caves — Olwolgin Upstream and Burnabbie Caves.

This experience has enabled the exploration team to identify the fragile features and place the guideline so that divers, including themselves, avoid damaging them.

This strategy is supported by floating reflectors and signs that identify the feature and ask divers to swim directly above the guideline for a short distance around it.

And so it is that underwater track marking has been implemented with the hope of conserving these unique and spectacular features for future generations to enjoy.


UPDATE: NOVEMBER 2013

Anzac Parade

Spurred on by the tantalizing discovery of Grand Central by Chris Edwards and Grant Pearce during the Easter 2012 trip, Alan Polini and I organised another Raid trip for four days later that month. Only an act of God would keep us away from the Nullarbor at this stage and even then, He’d have to make a pretty good effort.

Driving through the night of 24 April, we arrived on site on Wednesday morning, the 25th (Anzac Day). We immediately wheelbarrowed everything out to the cave: scooters, cylinders, compressors, generator, food and fuel.

After a set-up dive to stage cylinders and scooters in the cave on the Wednesday afternoon, the cave was set for some serious diving commencing early the next morning.

The aim of the first push dive was to explore Grand Central, specifically to the south-west, in line with the main passage development trends seen so far in the cave.

Alan recalls this memorable dive: ‘Upon arriving at Grand Central and after looking around its impressive size, we continued with our plan of checking extensions to the south-west. This is where we left Grand Central and entered a massive section of cave tunnel.

600 m of diving passages

‘It was a good thing that we each carried a compass; we needed them, as the sheer size of the Anzac Parade tunnel made the high-powered lighting systems we had virtually useless. Don’t get me wrong; it was great to be laying line in what is and could quite possibly be the largest unexplored passage I will ever experience, but a shame that we could barely see the walls. Just like floating through space, we unloaded the line off the reel screaming and hooting at each other.’

Olwolgin passage. Liz Rogers photograph
Olwolgin passage. Liz Rogers photograph

More than 600 m of impressive diving passages were explored and surveyed over the next three dives in this area.

On our second last dive of the Anzac Day Raid, Alan and I redirected our attention to the end of the A Tunnel to close out some leads there.

Although the leads we looked at were largely fruitless, on our way back we both made separate, significant discoveries on the sidewalls of Ags Dreamtime.

Alan explored and surveyed 250 m of stunning virgin passage on the eastern side — Gentlemans Lead — while I discovered a roof hole on the western side with a large, wide, 200 m long tunnel that proved to be a short cut to Grand Central.

More importantly, the short cut was big enough to facilitate a direct transit from the staging area through to Anzac Parade with scooters and backmounted rebreathers.

Exhilarating, but exhausting

In three days of highly focused exploration diving, Alan and I spent 16 hours each underwater. This enabled us to add 1800 m to the surveyed length of the cave and extend the maximum penetration distance to over 1250 m — exhilarating, but exhausting indeed.

Olwolgin passage. Liz Rogers photograph
Olwolgin passage. Liz Rogers photograph

Further efforts by two different team visits later in 2012 (including Alan & me) failed to find a continuation of the cave to the south-west but added a further 700 m of passages, most notably The Kraken, a 300 m long side passage from the Gentlemans Lead which connects through to the end of the A Tunnel and features some of the most extraordinary bacterial ‘webs’ seen in the cave.

The Kraken was discovered and named by Alan Polini and Rod O’Brien (SUSS) who both have large tattoos of a kraken on their bodies. At this point, the name of the cave where all the new cave diving discoveries had been made was revealed as Olwolgin Downstream during a presentation at the CDAA AGM in Mount Gambier, at which point the surveyed length stood at 5100 m.

The total cave diving passage length of Olwolgin Cave was then at 7800 m.

Olwolgin map 3
Olwolgin map 3

We were starting to think that we had exhausted the main exploration of the cave and hopes were low that we would find a continuation to the south-west. All the big tunnels at that end of the cave terminated in small, low, flat, silty areas — generally uninviting areas for cave divers.

Our next major trip was planned for Easter 2013.

Breakthrough

Once more, Alan and I were back, but with a continuation of the cave now highly doubtful, we turned our attention to surveying the remaining line in the cave, pushing small leads and bushwalking the surrounding area for new caves to dive. The surveying helped to fix some errors in the survey and a few small leads added 500 m to the map.

The bushwalking revealed a couple of new karst features but no new caves to dive. As Alan went back to work after four days of diving, brothers Ryan and Michael Kaczkowski joined me in his place and began familiarising themselves with the cave system: Upstream and then Downstream Olwolgin.

During the course of surveying some small and silty tunnels near the end of the cave, I noted some fascinating patterns of speleogenesis that were repeated in areas of the cave separated by many hundreds of metres. These patterns helped me to reappraise my understanding of the cave’s structure and development, giving me new hope of finding a continuation to the south-west.

With the possibility of the continuation firmly in mind, I set off on a dive to the end of the cave. Before I left, Ryan asked, ‘So, are you going to look at some new holes or areas to try to find an extension?’

‘No, I’m going to look at old areas, but with a new attitude.’

The unexpected breakthrough

The first two hours of this dive were spent exploring and surveying 200 m of small new passages near the end of Anzac Parade which matched the expected profile but were not the hoped for extension.

The breakthrough came when a low, flat, silty room (it was, in fact, the very first place Alan and I looked at when we were exploring 12 months before) was revisited and traversed straight through for 50 m before it opened up into a large conduit heading directly to the south-west — the continuation had been found.

A further 100 m on, my thirds gas limit was reached and the line was tied off on a boulder pile in the middle of a large intersecting passage with no end in sight either to the left or right. This was an absolutely perfect way to wrap up the dive and survey out.

Ryan and I spent the next two dives exploring and surveying over 500 m of passages in this new area named the Easter Extension after a similarly named section of Mullamullang Cave.

Ryan spotted a skull and full skeleton of a dingo amongst the rocks at the intersection tie-off (Dingo Junction), no doubt washed in from the surface feature we were now in the vicinity of.

A large room full of thick, brown silt and incredibly dense drapes of bacterial matting was briefly surveyed and checked for a surface connecting hole before being left from further disturbance.

Amazing, but fragile spectacle

Sign for a fragile site
Sign for a fragile site

Ryan provided the following impressions of the cave after a week of diving. 'I found the cave impressively large, considering the crappy little entrance hole. Especially remarkable are the large rooms toward the back of the cave (Grand Central and Anzac Parade) where the dark cave walls and distortive water seem to swallow up light from even the brightest torches.

'It’s amazing to dive through a number of large tunnels which are all connected through excellent sidemount passages. The new section, once again, was impressive to arrive at after traversing through a much smaller cave tunnel and then popping up to a large junction with yet another tunnel seeming to boom off left and right with small, low rooms branching off its sides.

'While diving Olwolgin Cave you get to experience very different characteristics compared to other Nullarbor sites and the varying size and length of the passages can’t help but make you wonder what’s happening under your feet right throughout the Roe Plains.'

The Easter 2013 trip added another 1700 m of surveyed passages to the cave making a total of 6300 m for Downstream Olwolgin and 9200 m for the total system. The maximum diving penetrations were now at about 1300 m.

Olwolgin map 4
Olwolgin map 4

The Adventure Continues

Discussions were had with an experienced group of cave divers from the CDAA in late 2012 regarding access to and protection of the cave for suitably experienced and qualified CDAA members.

It was agreed that the line in a number of areas would need to be cleared up or removed, more signs placed, and that clear junction marking (with tags) similar to the system used in Tank Cave would be needed.

We also needed to ensure there were line arrows every 50 m or so throughout the cave.

In July 2013, a lot of this work was done by Ken Smith and Neville Skinner in both Upstream and Downstream Olwolgin.

Grant Pearce and I used sidemount rebreathers to continue exploring the Easter Extension area and added another 300 m of small, maze-like passages there, but we found no major continuation.

When we left, there were only two leads identified by Grant and I that had any promise of finding a way through and they were strictly sidemount access as well as deep in the cave). Run times of 3-4 hours on these dives were normal.

Taking up the challenge

With the rest of us committed to work and family, Ryan and Michael Kaczkowski, together with Sam Vermey, took up the challenge in the first week of November 2013.

Grant and I received very excited phone calls from Ryan as he was passing back through Eucla on his way home from the trip: ‘Great Success!’ Ryan describes their experiences. 'Sam loved the cave and we spent the first few days getting him familiarized with the passages. I was very eager to get out the back though, of course. Once we got out the back we quickly got onto Grant’s reel. We passed through two close-tight restrictions then it pops out into nice big passage which runs NE and SW. Great! Ran about 110 m in a straight line and surveyed it out.

'Next dive we looked for leads. Sam reeled out into a couple of offshoot passages (which we surveyed). I saw a hole dropping off to the south-west on my way out which I had missed and the next dive had a look and, yes, it just took off.

'It is a really beautiful section of the cave, like a maze or forest of limestone. Plenty of leads so just headed SW and it kept going. After I reeled through a lower silty section I started following larger passage … I am sure it keeps going but I had no time to push it. Must return with scooters. Long swim. Ha!'

Congratulations were in order; together, Ryan and Sam explored and surveyed 300 m of passages in the new ‘Stone Forest’ section, extending the maximum penetration distance to approximately 1500 m and best of all, still going.

We are hopeful that this new section will enable continuation into the main conduit to the south-west beyond the collapse doline and cave that is clearly obstructing the main passage near Dingo Junction. Pinger data obtained in July 2013 showed this area to be only 50 m short of the surface doline and cave from where the dingo skeleton was most likely washed in.

In Summary

During two short but intensive years of exploration, Downstream Olwolgin has revealed over 7000 m of new cave diving passages and provided all those involved with some amazing and unforgettable experiences.

Exploration of the whole cave system over the past ten years has involved a lot of work as well, with over 900 survey stations and 33 pinger points recorded. We have also placed numerous underwater conservation signs, reflectors, dozens of junction markers and countless line arrows. Olwolgin Cave currently has 9900 m of surveyed passages, placing it among Australia’s longest underwater cave systems such as Panniken Plains, Tank and Cocklebiddy Caves — deserving company for such a spectacular cave.

Olwolgin map 5
Olwolgin map 5

The author would like to thank all those who have helped and contributed to the exploration of this magnificent cave system to date.

The beautiful underwater photos taken by Richard Harris, Liz Rogers and Chris Holman have helped convey the stunning beauty and fragility of the Roe Plains Caves — thanks, guys.

And, of course, for the use of the pingers which enabled us to correct our survey data, we are entirely indebted to the inimitable Ken Smith whose fart joke and accompanying peals of laughter will echo across the Roe Plains forever!