Conceptual Drainage Design of an Urban Rail Transit Project

Abstract

AbstractUrban rail transit systems in Canada have been undergoing expansions in recent years. Many of these expansions are routed through existing developments and neighbourhoods with congested underground utilities. The installation of new rail lines requires new servicing infrastructure and relocation of existing utilities which can become quite complex. Additionally, new stations and platforms create more impervious surface which results in increased runoff; stormwater management strategies are needed to mitigate the impacts of this additional runoff on the existing drainage systems to prevent increasing the risk of flooding. This project included the conceptual design of the drainage and stormwater management systems, including identifying utility relocations. The proposed rail line consisted of an at-grade light rail line with crossings both at-grade and below-grade, which affects the stormwater management strategy. The proposed rail line alignment would intersect with developed neighbourhoods that were serviced by a mix of separated sewers (where water flows in separated storm and sanitary pipes) as well as older developments serviced by a combined sewer area (where storm and sanitary flows are carried within the same pipe). The proposed Light Rail Transit (LRT) design was analyzed from a drainage and stormwater perspective and included runoff volume calculations and flow increases. Several mitigation opportunities were identified, including low impact development measures, integration with existing and proposed regional flood mitigation measures, and underground storage. Conceptual infrastructure designs were prepared from the mitigation opportunities based on preliminary construction feasibility considerations and iteratively integrated with the other disciplines’ design elements on the project.