In just twelve days, with only Christmas Day off, Prime Pump completed a major task: pumping 6,000 cube of silt 650 metres up a steep and challenging site, with a physical head of 55 metres.
The goal was to de-silt a series of the five ponds that are a key part of the settling system for successful Dunedin-based rock quarrying business Blackhead Quarries. Prime Pump’s work was scheduled around the busy quarries’ annual shutdown. The quarries’ gravity-fed ponds act as clarifiers, removing the sediment that results from run-off, and washing down the gravel harvested from the quarry ready for commercial use. The system, which prevents any dirty water reaching the natural waterways, is self-sufficient and even provides fresh water-take, so their own water can be recycled.
Previous efforts to remove the silt, which has built-up over 25 years, using excavators and dump trucks had proved inefficient and costly. Operating the trucks on the steep terrain added risk and meant a sizeable amount of slurry overflowed from each load. At the core of Prime Pump’s solution was an excavator-mounted, Italian-designed and manufactured Dragflow HY85-160. Able to handle up to 70% solids by weight - a higher concentration of slurry versus water than any other pump in its league - this super heavy-duty submersible agitator pump efficiently handles slurries with highly abrasive solids. Those attributes make it perfectly suited to tough jobs like Blackhead Quarries.
The Dragflow pumped the sludge 500 metres, with a 45 metre vertical head, to the booster pump, a Netherlands designed and manufactured BBA BA180 diesel pump, which took the sludge up another 150 metres with around 10 metres head.
The economies over excavators and dump trucks were significant. More slurry was moved more quickly with less risk of spillage Prime Pump’s Special Projects / R&D Team Leader Brent Petrie says the project was highly technical. “It’s very strategic working out where exactly to place the booster pump. You have to take into account weight of solids per cubic metre, hydraulic flow, and pressure. There’s the risk of blockages or even pipes bursting.
It’s a whole different story to pumping water.”
Two to three Prime Pump staff were on site every day of the operation closely monitoring the process and using drone surveillance to document environmental compliance. But Hayden Powell Prime Pump Sales TL Civil & Hire, says the bulk of the man hours were in laying the 650 metres of pipes required to do the job.
He says it was well worth the effort. The client was “stoked” with the outcome; the ponds should be good for another 5-7 years, and Prime Pump pumped almost exactly twice the volume of silt in the time than initially expected. “Everyone’s really happy.”
