This past Monday we began a slightly more typical week. There is a lot that needs to get done before the start of the “season”, and not much time to do it.
The big focus of this week is getting the systems in the OSL dialed in. Allow me to explain the basic outline of how the lab works:
This year, we have a new Sediment-Feeder. It is an auger that brings up sediment from the Sed Tank, which then spills into a funnel, accompanied by a jet of water to flush it down and into the stream
- We control how much water enters the head-box at the top of the section of stream. Water comes straight from the Mississippi, and we turn a large valve to determine the flow rate.
- At the same time, we adjust the rate at which sediment is fed into the stream system–which is also done at the head-box.
- Water+Sediment flows through stream.
- The sediment is dumped by the water into one of three bays in what is called the ‘tail-box’. The stream water flows down to rejoin the Mississippi.
- We move the sediment back to the top of the stream, after analyzing how much was deposited en-route.
This year, we have a new Sediment-Feeder. It consists of an auger that brings up sediment from the Sed Tank, which then spills it into a funnel, from whence it is flushed down with a jet of water.
Our sediment is stored in a huge 2,500 gallon tank that sits near the head-box. They are very particular about making sure that none of our sediment gets lost, which I can understand. The rod you can see to the left of the tank on the ground has a tape measure attached to it so that one can measure how much room is left in the tank:
The auger is driven by a motor, and thus the sediment feed-rate is determined by the motor speed. Unfortunately, I’ve been told that the current gear-box is inadequate, as we only end up running the motor at about 3hz, which apparently is bad (too slow) for motors. So, every once in a while the Sed Feeder gets jammed, and the auger stops spinning. In order to get the system going again, we’re supposed to just get this HUGE wrench and give a good rotational yank to the auger-shaft to try and unstick it. At first I was worried about doing this, thinking that perhaps something in it could get broken, but I no longer care. This whole system was designed and built by Dick, who works at SAFL. Pretty ingenious!
A lot of what we were doing early on this week was trying to figure out what we need to set the motor at in order to achieve the golden rate of sediment dispersal of 8L/2min.