Stormwater treatment through planter boxes for contaminants originating from metal roofs at the Annacis Island warehouse Skaloud, Paul
The purpose of this report is to provide options for stormwater contaminant treatment from metal roofs at the Annacis Warehouse, a site under Port of Vancouver jurisdiction. Specifically, this project looks at how existing planter boxes, which are rain gardens in a box, are potential treatment solutions for exceedances of heavy metals in current stormwater. These boxes are capable of treating and removing various contaminants from stormwater through mechanisms including adsorption and vegetative uptake. The following report argues for the implementation of a pilot planter box at the site, given support from academic literature, expert interviews, as well as various case studies using similar technologies. In order to implement a planter box, various variables need to be considered. A few of these include size of the existing site and the box, installation requirements, local meteorological conditions, bioretention media, and the use of specific vegetation. As every site is different due to the variability of metal roofs and local water quality guidelines, planter boxes need to be carefully selected or built in order to increase the likelihood of successful treatment. Academic literature supports planter boxes for the treatment of stormwater runoff from metal roofs, but does tend to focus on galvanized iron roofs and treatment options for high levels of zinc. Two expert interviews were conducted with Jennifer Foster of KWL Engineering and Michael MacLatchy of Associated Engineering. These interviews have provided recommendations on maintenance requirements and other variables. Examining case studies in other areas of the Pacific Northwest is also used extensively in this report, with other ports and industries also looking to treat metal roof runoff through the use of planter boxes. This report will argue that the Port of Vancouver install two planter boxes with slight differences at the Annacis Island Warehouse based on the general design of the ‘Grattix’, a planter box initially built at the Port of Vancouver in Washington, USA. With slight modifications, this planter box is most viable at the site due to its low cost, easy installation, and use of native materials. Maintenance requirements as well as avenues for further research are also emphasized towards the end of the report.
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