Have run a permanent drain down the gully so the roof runoff will all go direct to the soak hole/pond. Now I can plant vines all along the fence and also gradually increase the surface area of pond. It soaked away last time so if I want it to stay full I will have to compact or smear it. Ive read that fermenting vegetation on the bottom will seal it too. Two people have 'bought' the fill Ive dug out, saving me bin costs.