Topsoil Type 7 is a very specialized topsoil mixture that is used for Low Impact Development (LID) – Flow Attenuation/Water Quality Treatment end use (8). The chemical and physical properties of this topsoil type have been adapted from various sources including the above stated resources with the addition of the City of Edmonton LID Best Management Practices Design Guide, Edition 1.1 (2014), Liu (2014), WSU and Puget Sound Partnership (2012), and San Francisco Regional Water Board (2011).
The higher sand content (50-85%), low silt and clay content (maximum 20%) combined with the higher organic matter (5-10%) should improve water flow and water quality in the facility.