CAVE DIVERS ASSOCIATION OF AUSTRALIA (INC) RESEARCH GROUP

RESEARCH REPORT NUMBER 4

“ENGELBRECHTS CAVE” (5L19/20) MAPPING PROJECT - 1986

This report was prepared by the CDAA's Manager of Mapping & Research, Peter Horne, in January 1994 through the efforts of members of the Cave Divers Association of Australia's Research Group Engelbrechts Cave Survey Team.

Enquiries should be forwarded to:Mr. Andrew Cox (or the CDAA Directors) CDAA Engelbrechts Cave Survey Co-Ordinator C/- P.O. Box 290, NORTH ADELAIDE S.A. 5006

or the author C/- 12 Addison Road, HOVE, S.A. 5048, AUSTRALIA.

No part of this report or the associated maps may be reproduced by any means without the written consent of the CDAA or the author, and all such reproductions must acknowledge the CDAA as the information source. (*This digitised version of the original report was prepared by the author in 2005 and updated with maps in 2010 so that it could be made more readily available electronically to interested parties.)

************************************************************** ISBN 0 646 19258 2 COPYRIGHT (c) 1994 CAVE DIVERS ASSOCIATION OF AUSTRALIA (Inc).

FOREWORD This report was prepared to enable interested readers to gain some idea about the work which was put in by cave divers in their endeavours to survey and explore Engelbrechts Cave, which is now a major tourist attraction in the heart of Mount Gambier, South Australia. ACKNOWLEDGEMENTS A considerable number of people volunteered their time, money and scientific, speleological and cave diving expertise to enable Engelbrechts Cave to be mapped in detail. Firstly, thanks are extended to experienced cave surveyors Kevin Mott and Fred Aslin of the Cave Exploration Group of South Australia (CEGSA) and others who provided invaluable information about the exact location and structure of the entrance sinkhole; Dr Rod Wells (Senior Lecturer in Biology, Flinders University of S.A.) for his fossil-identification work; Andrew Emmett, the Regional Chemist (South East) of the Engineering & Water Supply Department, for water analysis work, and CEGSA for providing additional interesting historical information and photos. All of this material and support provided an invaluable baseline reference for possible future researchers, and these efforts are very much appreciated. Of course, the underwater regions of the cave would never have been explored - let alone mapped - if it hadn't been for the interest shown, and effort expended, by cave divers. The following CDAA members are especially thanked for their efforts which often involved spending many hours working in cold, low-visibility conditions:Brenton WOOLCOCK Anne WILSON Ross WALKER John VANDERLEEST Peter ROGERS Tony RICHARDSON Nick JONES Frank HOMEWOOD Tony HAMBLING Noel DILLON Rino DELL'ANTONIO Andrew COX Trevor BURFORD Anne-Marie BURGOINE Chris BROWN Cheryl BASS and Paul ARBON As Coordinator of this study, Andrew Cox also spent dozens of hours compiling data, keeping the Research Co-Ordinator (Peter Stace) advised of developments, and undertaking many difficult mapping dives himself, and it was ultimately through Andrew's efforts that this study was completed. Finally, the cooperation of the Corporation of the City of Mount Gambier (especially Town Clerk Greg Muller) and members of the voluntary organisation “LIFELINE” is herewith gratefully acknowledged. Thank you again to all who assisted! Peter Horne MANAGER, MAPPING & RESEARCH, 1994.

INTRODUCTION Until the early 1980s, Engelbrechts Cave (official cave reference number 5L19/20 - Cave Exploration Group of South Australia) was generally believed to be nothing more than a rubbish-filled, limestone-walled 'sinkhole' in a cleared paddock in the City of Mount Gambier, like so many other “karst” features in the “Green Triangle” region. Easily seen by travellers on “National Highway One” in an open paddock to the south between Ehret Street and Victoria Terrace, the cave has only recently been beautified to make it perhaps the best tourist-cave feature in the city ... and one of the most exciting and interesting cave dives in the country.

Figure 1: Location of Engelbrechts Cave, Mount Gambier, South Australia.

A BRIEF HISTORY (Sources: Engelbrecht Cave Information Booklet, Kevin Mott & Fred Aslin, Sep. 1992; various “Border Watch” newspaper articles; information supplied by local historian Les Hill; and numerous notes by cave divers and the author, 1979-93).

Engelbrechts Cave was first described by the Reverend Julian Tenison Woods in his acclaimed “Geological Observations of South Australia” in 1864, where he referred to the feature as “Vansittarts Cave”. (Also in that year, an exploration party consisting of Dr Wehl, John Stafford, Charlie Brad and Albert and 7-year-old Charles Grosser reportedly followed a fast-flowing underground stream in the cave for about 200 metres; however, the vastly different description of this feature from its known form today leads some people to believe that this party might in fact have explored another near-by feature which has subsequently been lost.) 1

In 1868, Carl Engelbrecht, a 35-year old German immigrant, settled in Mount Gambier (by way of Port MacDonnell a few years earlier), where he opened a store which he ran until 1885. He then purchased an old flour mill owned by Dr Wehl and converted it into a whiskey distillery, and it was the use of the sinkhole as a handy rubbish-tip for many years (mainly for disposing of “slimper”, a caustic by-product of the distillery process) which associated Carl Engelbrecht's name with the feature. The distillery was closed in 1903. Although other explorers more than likely visited the cave on numerous occasions after its discovery, the next major known (reported) event occurred in 1940, when Cr R.J.R. Watson used a rope ladder to climb more than 11 metres down into the main lake chamber. The water was found to be about 6 metres deep and extremely clear, and it was around this time that a decision was made to divert local storm-water runoff into the cave.

Photo 1: The rubbish-filled entrance doline of Engelbrechts Cave as it appeared a decade or so before the cleanup (CEGSA, circa. 1970). The sinkhole entered CEGSA's cave records in December 1954, when a reference nail was installed to monitor water level fluctuations, and ten years later, in April 1964, the first known underwater cave exploration took place when pioneering cave divers Phillip “Mick” Potter (Mount Gambier) and Dave Burchell, Ross Curnow and John Lees from Adelaide penetrated the “Eastern Side” section for about 45 metres. The relatively unpleasant nature of the dive (for those days!) prompted them to state that the feature had, in their opinion, no tourist potential ... and interestingly, they found “J.A. Cook 1864” scratched on a wall which could only have been reached by boat or swimming. The modern-day underwater adventurers then duly added THEIR names to this century-old inscription as well!

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The first map of the feature was made by local speleologist Fred W. Aslin in April 1966, and in October 1974, the local Lions Club leased the area for a historical display. In 1979, the Lions Club commenced the beautification project in the feature, and within a year many tonnes of broken glass and other rubbish (approximately 400 cubic yards) was removed from the sinkhole's entrance. Around the same time that this cleanup was commencing, cave divers Peter Stace, Phil Prust and Ron and Robyn Allum decided to assess the site again the first visit by divers in 15 years - whereupon they promptly discovered the Eastern Side's large air-chamber. Later, in May 1979, Ron squeezed through what was then a very tight, silty and unstable tunnel in the small pool on the Western Side, where he discovered that the passage opened up, although he couldn't see a thing at that stage. After the water had cleared, Phil and Peter worked their ways through the restriction and explored the 100-metre long submerged passage which headed off to the north-west, but they didn't notice the large air chamber which existed at the end of the passage; this discovery, along with the existence of other flooded passages in this area, had to wait until Ian Lewis and Terry Reardon visited the site sometime shortly afterwards.

Photo 2: Very wide-angle perspective view of the entrance area of the cave shortly after the first cleanup (Andrew Cox, circa 1986).

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Overall, these efforts resulted in the realisation of a major cave system in the very heart of a city of more than 20,000 people and directly underneath a number of houses and a main highway, and the CDAA subsequently initiated negotiations with the Corporation of the City of Mount Gambier to enable properly-qualified and highly-experienced cave divers to visit the feature on a regular basis for recreational purposes.

Photo 3: Interpretive sign on the stairway leading into the cave (Andrew Cox). The first comprehensive legal agreements and indemnities were drawn up so that all involved parties could be protected as much as possible, and these became the forerunners to the legal process which is now commonly used by the Association to obtain access to a number of other important cave diving sites in this district. This, then, was the lead-up to the mapping project in Engelbrechts Cave by the Cave Divers Association of Australia's Research Group in 1986.

PRODUCING THE MAP The surveying project was originally scheduled for a total of eight weekends between 17th May and 24th August 1986, and during this period many dozens of dives were performed. With the introduction of new cave diving standards for the higher-level features around that time, many divers were equipped with twin-independent scuba cylinders as well as fibreglass measuring tapes, knotted lines, nails, pegs, hammers and hand-held or board-mounted underwater compasses and notepads (“slates”). 4

To measure the height of the air chambers, helium balloons were floated on thin lines to the ceiling in places, and various skeletal remains of long-extinct Australian animals were collected (along with a number of water samples) from various locations.

Photo 4: The Eastern Side's lake chamber, as seen from the tourists' viewing platform (Andrew Cox).

Photo 5: A section of the underwater passage on the Eastern Side (Mark Nielsen). 5

The surveying usually involved two or more divers positioning themselves at reference stations and running tapes or lines out to other stations before measuring their forward and backward bearings and changes in depth (to within about half a metre, using standard divers' depth gauges). From such baselines, details about the shape and width of the walls, floor and ceiling were drawn in, enabling Andrew to plot it all up and identify errors or gaps in important data so that future dives could be productively planned. The surveyors were confident that their efforts were quite accurate, and only a small number of possible discrepancies were identified with respect to how surface features related to the underground network. It is hoped that further underground surveying, and the utilisation of suitable RDF (radio directionfinding) equipment, transmitting from perhaps the big air chambers, will further enhance the accuracy of the map in the future.

Photo 6: Surfacing in the Eastern Side's remote air chamber (Mark Nielsen).

FOSSIL DISCOVERIES A number of sub-fossil specimens were collected from various areas within the cave and Dr Rod Wells at South Australia's Flinders University identified a jaw from a Protemnodon kangaroo (possibly P. raechus); the skull and lower jaw of the common wombat (Vombatus ursinus); the pelvis, femurs, distal lumbar and sacral and caudal vertebrae of a Macropus kangaroo, and the jaws of an adult eastern grey kangaroo (M. giganteus). A letter from visiting Tasmanian cave diver Stefan Eberhard (Feb 1986) also related to his discovery of sub-fossil bone deposits in a clay matrix-filled solution cavity, where he found a possible femur of a Pleistocene megafaunal creature, so further work in this area of research is also warranted.

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Photo 7: Surveying and exploring in the Eastern Side air chamber, beyond the main lake (Mark Nielsen).

Photo 8: Looking down the steep slope into the Western Side of the cave (Andrew Cox).

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Photo 9: The relatively tiny entry pool on the Western Side (unknown photographer, picture courtesy Andrew Cox).

Photo 10: A cave diver preparing to explore the huge flooded passage which leads off from the Western Side lake (Neil Vincent).

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WATER SAMPLES A number of water samples were collected from within the cave during this study, and these were analysed in Mount Gambier by Andrew Emmett. His report, dated December 1988, showed that the level of Nitrate pollution was very acceptably low (around 9.5 mg/l), Phosphate (as P) was about 0.02ppm; Copper ranged from less than .005 to .009; Lead was around .001; Zinc ranged from less than .005 to .013; and Dissolved Organic Carbon was about 1.3-1.7 mg/l. Also, nothing was detected from some general organic scans which were carried out.

Photo 11: A diver standing in the large Western Side air-chamber, a few years prior to the CDAA's now-mandatory “twin-independent cylinder” rule for Penetration-rated cave divers (Karel Lengs).

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DISCUSSION Engelbrechts Cave is today rated by the CDAA as two separate diving sites, due to the differing nature of its flooded passages and underwater constrictions. The “Eastern Side” chamber (5L19) is classified as “Cave” level, as it is mainly silty and low, and in all but a couple of places, cave divers can keep in close contact with each other; and the “Western Side” (5L20), commencing at the bottom of the entrance chamber in a small pool of water, is classified as a “Penetration” level dive because of its much longer underwater distances and silty restrictions. Apart from occasional low-visibility water in the Western Side (caused by inflow from a nearby stormwater drain near the highway), the entire system contains fantastically-clear water which makes exploration of the enticing tunnels and wide passages a real joy for properly-trained and equipped cave divers. Engelbrechts Cave is one of Australia's most important and spectacular cave diving sites, and the support shown to the CDAA by local community groups and the Corporation of the City of Mount Gambier by allowing cave divers to gain access to this fascinating feature will always be very much appreciated!

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For further information about this and other cave diving matters and projects, please contact

Cave Divers Association of Australia, P.O. Box 290, NORTH ADELAIDE S.A. 5006.

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