Many small blocks on unsewered towns are over developed with not enough space or funds for proper onsite wastewater management and containment. Sometime neighbours have constructed dams, bores or wells too close and have prevented the use of what space there might have been available. Trees have tremendous wastewater nutrient and volume take up potential but the technical difficulty has been how to apply the wastewater without the tree being destabilised or rotted, the delivery/application system being blocked with particles or tree roots and wastewater being made available but in a way that holds back the wastewater at times when the tree does not need it so the excess wastewater does not overflow and escape into nearby street drains, stormwater systems or dams. The EPA setback distances exist for wastewater applications systems that have no potential for hold back of flow, maybe smarter systems could be placed closer to these sensitive land uses. Traditionally the EPA have suggested staying outside the drip line of large trees with conventional wastewater application systems but if the right ways of harnessing this environment could be found then the bonus transpiration, shelter from high rainfall and effective double dipping by planting some other water loving plants around the base of the tree (where normally most plants die off often due to lack of water not falling from above and being drawn away by the roots below. What would be the optimum street or reserve tree for this purpose? I had paperbarks in mind - common native street tree with not a huge root systems. The greywater, wormwater or blackwater (from a septic tank) application system I suspect would need to be held back to an elevated storage tank by a ball valve arrangement. There may even need to be two ball valves involved if there are two levels of sumps which wastewater is being applied to below ground. The sumps I had in mind were old tyres cut in half around the perimeter so they held water and made it accessible to plants and wick effects but would not "overflow" so to speak. To prevent root blockage I was going to make sure there was a 100mm air gap at the application point above the water level. Legally we will need special lease or legal agreements with land holders to extend their wastewater systems off their property but these would hopefully be pretty practical and probably preferable to being forced to connect to town sewerage. Any comments or other suggestions ?