I went on a solo mission today as it is near where I live, I noticed it years ago because we used to launch my mates boat there but only remembered it today.. its in the Oatley Bay area.
I saw a few Cave Clan references and saw the word meaty a few times so I'm not sure if it goes by the name meaty, hopefully someone can shed some light..
By the way that Eel scared the s*** out of me!
Enjoy..

Oatley Bay Drain by timatello, on Flickr
Entrance

Oatley Bay Drain by timatello, on Flickr
Entrance just inside

Oatley Bay Drain by timatello, on Flickr
Panorama just inside entrance

Oatley Bay Drain by timatello, on Flickr
View into the bay

Oatley Bay Drain by timatello, on Flickr
First manhole exit (not sure if it/where it opens to)

Oatley Bay Drain by timatello, on Flickr
Graffiti

Oatley Bay Drain by timatello, on Flickr
Room at the end of the first tunnel, had to jump the wall to continue.

Oatley Bay Drain by timatello, on Flickr
looing back from where I entered this room.

Oatley Bay Drain by timatello, on Flickr
10 second exposure and torch light (will have to experiment more with long exposures more I think)

Oatley Bay Drain by timatello, on Flickr
Sitting on the wall

Oatley Bay Drain by timatello, on Flickr
This bastard scared the s*** out of me.. Eel.

Oatley Bay Drain by timatello, on Flickr
Another manhole I did not try to open

Oatley Bay Drain by timatello, on Flickr
after about a 1km it turns into this shape and you start going under peoples backyards.

Oatley Bay Drain by timatello, on Flickr
I poked my camera up through one of the grills and sure enough I was in someones backyard.. I didnt go any further at this point as I had to be somewhere else..

Oatley Bay Drain by timatello, on Flickr
not sure where this led, it didnt seem like a very big pipe.

Oatley Bay Drain by timatello, on Flickr
small junction room

Oatley Bay Drain by timatello, on Flickr
Hmmm it semed pretty dry at this point to me..

Oatley Bay Drain by timatello, on Flickr
Drain Selfie