STORMWATER
Deployment of first layer of Geoweb cellular confinement over RS280i high efficiency geotextile.
Constructing a new child care facility directly above its stormwater system By Justin Gouthreau
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uring the construction of the Mount Dennis Child Care Facility, Toronto’s largest and first net-zero childcare facility, the contractor faced significant challenges due to available space for staging and construction sequencing. They needed to operate a crane with outriggers during the building construction. The only space available on-site was directly above the belowground stormwater system, which needed to be installed in the early stages of construction. A solution was required to protect the stormwater tanks and reduce the ground pressure exerted by the outrigger over the tanks. The belowground stormwater infiltration system used was a Brentwood Stormtank 25 series. Its heavy-duty infiltration gallery was installed within the parking lot to collect surface water
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runoff and infiltrate stormwater to match pre-development conditions. This was a low profile 600-mm tank rated for HS-25 wheel loading. The point load of the outrigger was a cause for concern, and to mitigate the potential risk of damage to the system or the reduction of service life, the contractor reached out to Layfield for a solution to reduce vertical pressure above the Stormtank from the crane outriggers. Presto Geosystems provided a multilayer Geoweb system designed with Atra Keys & Clips to create a safe working pad beneath the outrigger. It is an advanced soil stabilization technology that confines infill material and controls shearing and lateral and vertical movement of infill material. The Geoweb system’s effect is immediate and works on the principle of hoop strength. It’s designed cross section included a layer of RS280i high-efficiency woven geotextile below two layers of GW30V6 150-mm cellular con-
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finement Geoweb , infilled with 20-mm crushed granular and topped off with a crane outrigger pad. The RS280i provided reinforcement, delineation and separation between the pad layer while the Geoweb provided confinement of the 20-mm crushed aggregate compacted fill material. This concept reduced vertical pressure from the crane outrigger to well within the HS-25 loading limit of the storm tank system. Installation of the system was efficient and took approximately one day to complete. The contractor was delighted with the ease of use and installation to address this challenge and comfort, knowing the below-ground storage tank was protected.
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Justin Gouthreau is with Layfield Geosynthetics. Email: justin.gouthreau@layfieldgroup.com
June 2021 | 25