Gibson Elementary School Rain Garden (2011) 
11451 – 90th Avenue, North Delta

Once a forest, now a roundabout 

Like nearby Annieville and Delview schools, Gibson Elementary occupies a site that was once densely-forested.  Many of North Delta’s salmon streams had their headwaters in this and nearby areas -- including McAdam,

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Once a forest, now a roundabout 

Like nearby Annieville and Delview schools, Gibson Elementary occupies a site that was once densely-forested.  Many of North Delta’s salmon streams had their headwaters in this and nearby areas -- including McAdam, Collings, Norum, Honeymushroom, Kendale and Knudson creeks.

Nowadays, stormwater from Gibson’s roof and parking lot is piped into Honeymushroom Creek.  Honeymushroom flows mostly in a culvert – the sad fate of many salmon streams – except for a short but potentially productive stretch just before it empties into the Fraser River.

The roundabout in front of the school offered a good opportunity to trap some of this stormwater runoff in a new rain garden, which would reduce pollutant loads and add to the natural groundwater flow to the creek.

Gibson Elementary at lower left of photo; Delview Secondary at upper right.    Looking down driveway from 90th Avenue to roundabout at Gibson entrance

Where there’s a will, there’s a way

It took 2 years of negotiations and planning, but Delta Engineering at last overcame 2 hurdles:  first, negotiating a drainage right-of-way so that municipal crews could work on School Board property; and second, designing a spillway that would bring additional water into the rain garden from 90th Avenue.

Here’s how that design works:

Runoff from 90th Avenue crosses the sidewalk in a trench drain, then flows down a spillway, into a small storm drain, underneath the pedestrian walkway, and through another trench drain into the rain garden.  Whew!

Trench drain from 90th Ave under construction    Spillway and another trench drain at left; direct flow from driveway at right

Planting time

After Delta had added 5 new trees to the roundabout, it was the turn of older students to plant shrubs, grasses, rushes and groundcovers.   Primary grades then mulched the entire garden with woodchips, which maximize water absorption and also protect against soil compaction, erosion and weeds.

We use arborist woodchips (from tree pruning or removal), which contain a “potluck” of wood types, leaves and needles.  Gardens thrive with this mulch.

Plant placement arranged by Delta staff and Streamkeepers    Mulching the garden with woodchips

Stunning ensemble 

We knew that the existing roundabout trees – already quite large --  would “anchor” the new rain garden nicely.  However, until just a month before earthwork began, we had no idea that the blank wall behind these trees was to receive an impressive “wild BC” mural.  Delta rain garden designer Sarah Howie chose plants that beautifully complement the mood of this mural.

Tantalizing glimpses of mural, when trees are in leaf    Winter provides full view of mural backdrop to rain garden

 As with all our rain gardens, we’re looking forward to seeing this one thrive and grow, as its plants and soils become increasingly efficient at soaking up stormwater runoff.

 

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