Traditionalpractices were designed to convey water as quickly as possible to the outlet, either through natural or built water courses, to prevent flooding especially during larger storms. However, urbanization intensified upstream quickly and widely with increased impervious surfaces and sources of , to a point where the additional water volume and load could not be managed by the receiving courses. The increased load can degrade the natural landscapes it flows through, damage built and even endanger lives. has to be slowed down, reduced and treated before allowing it to be conveyed downstream.
The aim of sustainablepractices also referred to as (GI), (LID) , or Best Management Practices (BMPs) is to treat as close to the source as possible, either by delaying or reducing the runoff and by removing pollutants from it before conveying it downstream. Common goals for these practices include having post-development volumes and peak flow rates match pre-development values or creating the capacity to retain the runoff from a 12.5 – 25 mm event.
LID comprises a set of site design strategies that minimize runoff by means of distributed, small scale structural practices that mimic natural or predevelopmentthrough the processes of , , harvesting, filtration and detention of . Usually, because one structure cannot treat the volume or the variety of pollutants for the entire drainage area, the is conveyed through a treatment train of a number of LIDs. These practices can effectively remove nutrients, pathogens and metals from runoff, while reducing the volume and intensity of flows.
The purpose of the LID Treatment Train Tool (LID TTT) is to analyze whether sustainable goals can be achieved through the implementation of LIDs. The tool is used to compare and pollutant loading for the pre- and post-development (with LIDs) scenarios using annual and event based simulations.
What is theTreatment Train Tool?
The LID TTT, which is free for users, was developed by Sustainable Technologies Evaluation Program (STEP Water), a partnership between Lake Simcoe Region Conservation Authority (LSRCA), Credit Valley Conservation (CVC) and Toronto and Region Conservation Authority (TRCA). The goal was to streamline the planning and approval process by selecting and organizing the results of the model simulations and comparisons in a way that is clear and aligned with Ministry of the Environment and Climate Change (MOECC) guidelines, thus eliminating any additional downloads or additional computations.