Rear sloping sites pose hydraulic issues for appropriate disposal of stormwater. In some instances, a charged line can carry sufficient energy from the eaves gutters to the outlet on the kerb. Given the nature of the charged line, council’s may require a hydraulic grade line (HGL) analysis depicting satisfactory use of this method. However, there are sites where a charged line won’t be sufficient, and thus will require an easement through a downstream property to an outlet. When a neighbour refuses consent in writing for an easement, we can propose the idea of an absorption trench system.

Absorption trenches function by storing and dispersing stormwater into the surrounding soil over the duration of a storm. Sydney provides a wide array of soil types and strata, with many localities having very pervious soil by where water can easily permeate through, while other areas offerless permeability. Designing of absorption trenches in less permeable zones become more complex, which may result in larger absorption trenches and in some cases development restrictions. Our plans consisting of a detailed design with relevant calculations for the specified storm event typically start at around $600 + GST and vary depending on the size, scale and complexity of the project.