From the location of this cache, you can see the very impressive ruins of the Old Pomeroy Mill. This structure was built on the banks of the Wollondilly and is a traditional waterwheel driven mill. It was built in the 1800's when grain was grown in the area. With grain being replaced by the grazing of sheep and cattle and the growing of potatoes plus the development of a large mill in Goulburn, demand for this mill reduced. By the 1920's it was already referred to as the "Old Pomeroy Mill" and photos from that time look very similar to current day. (p2 Sydney Mail 11 Feb 1925 - thanks to Trove NLA).
For 2WD, I recommend parking the car at the end of the dirt track and walking the 50 or so metres to the cache. I'm not sure how far along this track a 4WD can travel. Unfortunately, it was dusk when I got here, so I haven't walked down to the end of the track. Based on the satellite maps, the mill is on the other side of the Wollondilly, so may not be accessible from this track.