Bioswale 1 Quebec Street at West 1st Avenue, Vancouver Canada

(Bio)swale

Created at: 29 Apr 2022

Description

Tree Trench & Bioswales Quebec Street at West 1st Avenue, Vancouver Canada

Built along West 1st Avenue and Quebec Street, these features collect rainwater runoff from surrounding roads. Weirs in the bioswales slow water flow for use and filtration by plants in the garden, while stormwater tree trenches collect water underground in structures similar to soil cells. What little water the soils can’t absorb exits through the overflow, moving from the catch basin into the pipes cleaner than when it entered.

This is the first of the two bioswales considered for this thesis. Bioswale 1 follows a typical bioswale design with two inlets and one outflow curb openings. The second inlet is to the south of the first one and they are spaced by 6.85m (centerline to centerline). The outlet is located 6.51m (centerline to centerline) to the south of the second inlet. Each inlet has a sediment pad that is composed of a concrete slab surrounded by a river rock apron. The apron has the purpose of slowing down the flow into the bioswale and minimize erosion. Figure 3.6 shows the cross-sections of Bioswale 1. The fully detailed engineering drawings can be found in Appendix C. The practice is approximately 15.6m long and 1.1m wide (width based on base which is the smallest dimension). This bioswale allows a maximum ponding depth of 15.5cm before overflowing. The average depth of this bioswale is 0.51m. The soil used for this practice is the standard turf blend that is used by the CoV which is used across all landscape activities in the city. This soil mix is does not have any added biofiltration capabilities or nutrient retention additives. This bioswale practice has a 4” perforated underdrain that is laid at 0% gradient across the majority of the length of the practice. The underdrain is in the middle of the 20cm clear crush aggregate layer that is located between the bioswale soil media and the native soils. The perforated underdrain increases to a solid 6” pipe diameter that discharges to the stormwater sewer. A monitoring manhole was installed and attached to the underdrain in order to have space and access to the flow to monitor the outflows and water quality. A monitoring well was installed in this practice to track the water levels during storm events.

Bioswale 1 collects and treats an EIA of 630m2 in addtion to the approxiamately 17.2m2 of the bioswale practice itself. The catchment area includes a section from the sidewalk, bicycle lane, paved boulevard section. The boundaries were determined and calcualted by the GI Branch during design. I evaluated the boundaries in the field during the water quality sampling days. The areas are shown in Figure 3.7. The runoff drains to the curb’s gutter, which in turn is sloped towards the inlets. From the bicycle lane, the water drains directly to the practice. Quebec Street is centerline crowned with a slope that varies between 1% to 2%. The water drains to the side gutter and ultimately into the GICB


Samenvatting (Dutch description)

Tree Trench & Bioswales Quebec Street at West 1st Avenue, Vancouver Canada

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climatescan

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