Under the rainbow

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Main Pumps

The two main pumps on deck are capable of handling unwanted objects with a maximum diameter of 14cm, but just to be on the safe side the sieves near the top of the hopper are set to 10cm.

Sand and water are generally mixed 50:50, and at the time 

of our visit it was just over 1km to the Cat 336 (max. length here will be 2.5km requiring the use of a booster). 

Mission control is an office on the deck of the barge where an operator monitors several screens and high-tech computer software to ensure the right mixture and pressures. The operator is in constant contact with the Cat 336, to let him know when the water flow was about to start and when the sand is added. 

Specially developed computer software allows the operator of the 336 to layer a blanket of sand. The details are off limits, but what we can reveal is that the operator fills in a digital colour chart.

This is a crucial part of the work because the sediment must be compressed evenly to prevent pockets of peat from seeping through to the surface. Once the sand is in place and compacted, the water in the sediment is absorbed to the surface using specialist vertical drainage rigs.

A dozer, or wheeled loader, sometimes assists the Cat 336 when it needs to track forwards. Normally, when sand is pumped through rigid sections of steel pipe, an excavator inserts extra lengths as required without interrupting the flow of material.

This is not an option with the flexible pipework, so enough lengths must be joined together to empty the contents of at least one sand barge. The excavator can drag up to 70m of pipe behind it, but requires a bit of assistance from the dozer when tugging longer lengths.

Dedicated TSHDs work around the clock in 12-hour shifts. There is no need for a night shift at this job, and the Cat 336 works a single daily 12-hour shift from Monday to Friday.

It depends on the sand supply boats and the weather out on the lake, but the excavator spews out anything from 300 to 600 cubes an hour.

I returned to the site two weeks later to see the Cat 336 deposit a second layer of sand over the top of the first. It is not necessary to spray the material so far in front of it this time to create the land for it to stand on so the flow of material was not reduced at the end of the extension.