The Canterbury team was called in to service the largest storm filter in NZ. Comprised of 570 cartridges, this storm filter at Bells Creek in Christchurch treats an area of 160 hectares (for context, a normal storm filter varies between 1-10 cartridges and treats around ½ a hectare). It was made oversize to reduce the flood risk (a concern due to ground subsidence after the earthquakes) and to reduce pollution of downstream waterways.
What does that mean for servicing it? It took us two days to service 170 carts and required 5 team members on site, including our confined space team.
We used a large 10,000 litre vacuum truck to dispose 18.5 tonne per chamber of sediment with the total volume coming in at a whopping 37 tonne. This is only the first stage of this job; we will be starting the next stage in May 2024 and servicing the remaining 230 cartridges.