1. The best treatment of greywater occurs in the upper region of the topsoil
2. A well built and maintained mulch basin will not fail even if the system is abused (ie. grease and solids handling capabilities)
In winter, to reduce the ice buildup in the swale along the cliff edge, we usually let the greywater just spill out into the garden and soak in and/or sublimate. The garden soil seems to like it just fine.