On London Dock, we were looking for a solution to concrete washout on site. We did not think that using lined skips or deep drip trays was effective as quite often it would rain heavily and fill the skips / trays up quickly.
If the tray overloaded, the water would land on the ground or on a membrane we had placed under the lined skip / tray. The weather was poor, so the water would evaporate slowly. We were also requiring a constant stream of fresh water to wash out the concrete skips / chutes which added to our monthly consumption on water usage which we are always trying to reduce and minimise.
We excavated a trench in the ground (approx. 3000 x 2000 x 600) and lined the excavation with double skin of waterproof membrane. We then installed flexiduct sections from the base of the excavation past ground level. The excavation was then filled with pea shingle. A thin concrete slab as cast over the shingle to give a suitable working platform for operatives cleaning the concrete skips.
When washing out the chutes, water lands into the spill trays. If the spill trays overloaded, the concrete washout water filters through the shingle and settles on the membrane. The water building up beneath the shingle can be pumped out from the flexiduct and used to washout the chutes
This method reduces the risk of concrete washout spilling onto the ground from the lined trays, and allows water to be recycled and reduce site water consumption.
Entry submitted by St George
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