1.1 Draining and Sediment Removal

            Once the sediment trap is full it will be necessary to drain the trap and remove the now wet sediment.  As we know sands and fines hold water within themselves and drain quite slowly.  The sediment will act as a dam and retain any water at the inlet of the sediment trap.  To counter the retaining of water at the inlet we scrape out a miniature channel in the formed delta allowing the water to travel quickly to the outlet.

            At this point a small submersible pump is placed into the trap to drain the water that cannot pass through the outlet pipe.  Once the submersible pump has drained as much water as it can, typically leaving behind a half inch of water, a small hose is placed into the remaining water and a siphon is started.  A brick will work perfect to hold the small hose's opening face down to the bottom of the trap to avoid breaking the siphon.

            Now that the majority of the water is drained from the trap the sediment should now be piled up as much as possible to an accessible side of the trap.  The key is to reduce the base area of the pile, which is where the water will stay as it further drains out of the sediment to the base of the pile.  After an allotted time the pile should be checked on to see if the sediment has drained enough to be moved out of the trap.

            The point of all this work isn't to dry every grain of sediment in the trap but to simply to get the sediment 'not so wet'.  Trying to completely dry the sediment in the trap is, by trial and error, a waste of time and with a process that takes roughly a week to dry two tons of uniform 1.1mm sand, time is of the essence. 

            We remove the sediment with large plastic scoopers and place the sediment in four twenty liter buckets that will be loaded onto a gorilla cart to be transferred to the drying and bagging area.  It will most likely take more than one pass with a full cart to remove all the sediment and since all of the moving is by man power, grab a friend because you will sweat.

            Depending on the capacity of the drying and bagging area you have, you may not be able to move all the sediment to this location at once as we cannot here in our lab.  It impacts the efficiency of the final drying process negatively so move over a reasonable amount.  We fill our drying bins, which will be explained in section 1.6, to about a foot deep of sediment and cycle more sediment in from the trap as sediment is dried and bagged.  A small fan can be placed in the sediment trap to assist in making the sediment 'not so wet' while it waits to be cycled into the drying and bagging area.


1.2 Sediment Drying