| PROJECTS |
“Armitage believes PICP has an important role to play in stormwater control.”
(Above): The wetted patch of the Modified Swift test. (Right): Six litres of water are poured into the Modified Swift test bucket. (Below): Twenty litres of water are poured during the ASTM Standard test.
One of the requirements for maintaining a permeable interlocking concrete paver (PICP) system is a reliable, user-friendly method of testing water infiltration rates. This was one of the reasons UCT Permeable Paving Workshop leader Prof Neil Armitage and civil engineer, Peter Wium, as well as other members of the PICP workshop, spent a morning in February testing infiltration measurement devices at Cape Town’s Blue Route Mall shopping centre. Videos of each test were also made for the benefit of workshop members unable to attend. Three devices were tested: the Mod if ied Stormwater Infiltration Field test ( Mod i f ied SWIFT), the Modified Simple Infiltration test (SIT) and the American Standard test (ASTM Standard). They all gave similar values.
Quick and easy PICP INFILTRATION TEST
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PRECAST | ISSUE TWO | 2021
At approximately 35 000m², the Blue Route Mall’s parking area is the country’s largest PICP site. Installed in 2013, it has also been the best maintained and, as such, was the perfect setting for the infiltration tests. The Modif ied SWIFT test is based on Australia’s SWIFT test for permeable paving. It involves filling a bucket mounted on three 60mm legs with six litres of water and placing the bucket over the area to be tested. A plug at the bottom of the bucket is pulled, allowing the water to drain onto the PICP surface. The greater the area covered
by the water, the lower the infiltration rate and vice versa. T he wet ted area is est i mated by multiplying the length of the major axis of the damp area with its right-angled minor axis (ie, the area of the smallest rectangle enclosing the wetted area) and then reading off the associated infiltration from a plot linking this to infiltration. In the original SWIFT test, which was developed by Prof Terry Lucke of the University of the Sunshine Coast, Queensland, Australia, the infiltration was
