Storm water harvesting in Australia

Catching drainage water and reusing it in cities has been hard to achieve, thsi company shows how it can be down.
Annual cost for electricty in Melbourne , Australia was $200 in 2018
Stormwater harvesting

Considering how much of the system is underground, I am a little curious how the underground tanks would be maintained.

Like, in the gross pollutant trap, I would be interested in finding out how it gets cleaned and what happens to the stuff it traps. And how the sedimentation trap gets emptied during its use to prevent it from backing up and getting clogged.

From another source I see that the trap containers are cleaned with a truck powered vacuum unit.
Apparently it takes a few minutes for each, The gross trap captures large particles and the silt is caught in the other trap
I think if you go back and look at the main page with that website, that information may be there. I read about it elsewhere