UBC Undergraduate Research

UBC Stormwater Detention : Multiuse Stormwater Detention Infrastructure Chen, Hanpeng; Howes, Rebecca; King, Suzanne; Priest, Jordan; Van Der Mark, Nicola; Toi, Andrew


RAJNS Consulting has prepared final design of a multiuse stormwater detention facility for the University of British Columbia (UBC) and UBC Social Ecological Economic Development Studies (SEEDS) Sustainability Program. The project site is located southwest of the Centre for Comparative Medicine (CCM) at the intersection of Southwest Marine Drive and Wesbrook Mall in Vancouver, BC. The site is north of the Point Grey Cliffs which are susceptible to erosion from runoff and infiltration during storm events, which is a main constraint to design. Further, climate change and land use changes are exacerbating these issues. The design includes two distinct elements: a stormwater bioswale with underground water detention tank; and, a structural facility targeted for use by cyclists – a key project stakeholder. Three stormwater quality improvement methods are integrated into the detention centre. Upon review of past stormwater quality monitoring programs, it was determined that oil and grit separation is necessary to treat stormwater flows from the north and bioretention would provide appropriate quality improvements. Based on a hydrological and hydraulic analysis of the South Slopes Catchment, the detention chamber will consist of 20, 100 m long, 1050 mm diameter interconnected pipe lengths sloped 0.5% to the southeast which tie into Junction S6D-S26A at the inlet and Junction T6D-S25 at the outlet. This design combines natural bioretention soil and HDPE detention chambers to provide water storage in the event of a 100 year, 24 hour storm event. Through consultation with key stakeholders and considering themes of Resilient Cities, the detention centre will also feature a clubhouse for the UBC Thunderbird Cycling Club. Designed based on BC Building Codes and the National Building Code of Canada the clubhouse will feature showers and change rooms, a repair centre, and ample bicycle storage. Due to the scope of this project, structural design is limited to foundation loading, material selection, and placement planning. The estimated load of the building will be 22.5 kPa which will be transferred to a 1 m deep strip foundation founded on Site Class C type glacial till. The structure will be built with an emphasis on timber design and no retaining walls are required on the site. Located at the corner of Wesbrook Mall and Southwest Marine Drive the detention centre will act as a gateway to campus. Welcoming visitors, students, and faculty will be two precast concrete stormwater detaining Supertree structures incorporated with the UBC Gateway sign. The Supertrees, 2 m in diameter at the base, will be erected on 4 steel pile and cap foundation via a 4-dowel system to transfer their 7,535 kg load. Construction is estimated to take 8 months and should begin May 2019. An Environmental Impact Assessment (EIA) is not required for a project of this scale, however, RAJNS has identified potential construction-caused environmental concerns and presents mitigation options. The total estimated cost of the design is $16.34 million, including engineering fees and 30% contingency. The overall design established is a multi-modal and integrated hub for community and university cyclists, elevating UBC’s reputation as a global leader in sustainability. Disclaimer: “UBC SEEDS provides students with the opportunity to share the findings of their studies, as well as their opinions, conclusions and recommendations with the UBC community. The reader should bear in mind that this is a student project/report and is not an official document of UBC. Furthermore readers should bear in mind that these reports may not reflect the current status of activities at UBC. We urge you to contact the research persons mentioned in a report or the SEEDS Coordinator about the current status of the subject matter of a project/report.”

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