Chalmers Elementary School
Rain Garden (2009)
11315 – 75th Avenue, North Delta
A drainage problem
In addition to being environmentally friendly, rain
gardens are also an economical way of dealing with drainage problems.
Case in point: the entrance to the parking lot at Chalmers Elementary
School in North Delta.
Years of car and foot traffic had caused settling of
pavement and compaction of bare ground, with the result that large
puddles of rainwater and snowmelt regularly formed right beside the
parking lot storm drain.
Despite the puddles, the storm drain nonetheless still managed to take
in plenty of dirty runoff from the parking lot and pipe it directly into
Blake Creek, a tributary of Cougar Creek.
In short, it was a situation of inadvertent
“stormwater retention” that managed to cause significant
inconvenience yet still didn’t protect the receiving creek from
stormwater runoff.
A rain garden solution
Delta’s Engineering Department excavated a sunken
garden to receive and absorb parking lot runoff. They re-positioned the
storm drain – with a raised lip and surrounded by the rain garden – so
that now it sends only excess water (if any) down the pipe to Blake
Creek.
The garden design features a raised path of stepping stones, following
the shortcut route established by generations of students as they walk
to and from school.
The students themselves planted the mugo pines, heathers, sword ferns,
sedges, potentillas, roses and hens-&-chicks which fill their rain
garden. Neighbours too volunteered their services, helping out with the
planting and occasionally with maintenance (weeding, light pruning and
litter patrol).
Garden performance improves with age
Unlike engineered stormwater management structures,
which deteriorate over time, rain garden performance improves as plants
mature. Denser plant canopies trap more rainwater before it even
reaches the ground, and much of that water evaporates back into the
atmosphere. Expanding roots and their associated soil organisms
constantly create new porosities in the soil, making it capable of
soaking up more water.
Chalmers Rain Garden, our 2nd oldest school rain
garden in North Delta (after Cougar Canyon 1), is quite a small one.
Nonetheless, its performance has steadily improved as the plants have
grown and thrived with minimal care from Streamkeepers and students.
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Cougar Creek