The track to Growling Swallet from the end of Eight Road was put in by cavers in the mid-80s. The first picket is where the track joins McCullums Track. This track ran from Westerway, through The Gap, to The Settlement. It was also the alignment of The Great Western Railway to Strahan (which was never built!) The turn-off to Growling is the obvious turnoff just before a deep (4m deep anyway) dry valley. A stream can be heard to the left at this point.
The second picket marks another junction. McCullums Track continues for quite a way beyond this picket, but is not in very good condition as it's not often used by cavers. As Steve said, if you get to the enormous fallen tree, you've gone too far.
As a general warning, there are many taped lines in this area. Some of these lead to caves, others are survey lines. We cavers have little trouble following them. There is more information about Tassie caves at
http://www.lmrs.com.au/stcThe "tiny" entrance found by Steve is most likely Serendipity, the 10th deepest cave in Australia. (The 30 deepest caves in Australia are all in Tassie and 17 of these are in the Junee Florentine.)
Ric Tunney
Southern Tasmanian Caverneers