The first ponds are full.

You can start to see now how important the laying out of the ponds and tunnels was. The ground had to be built-up, the ponds had to be dug prior to the tunnel, as fitting large machines and removing the soil would have been impossible. To pre-position the ponds, and getting the tunnels to be central, only having 5' banks between each pond was a measuring task and times this by 14 and you can see that a few inches here and there could have been a huge problem.

But everything worked out exactly and Nick the ground worker agreed, my plan of working was the only way it could have been done. Pleasing now, but disconcerting at the beginning!

I'll add some more to this section in a while, but for now we go onto..........

The Concrete Ponds.

Time has come round to building the first 4 of 12 concrete ponds in the empty first tunnel, these are to be half in ground, half above. They are to be approximately 4mtr x 2.5mtr x 1.8mtr deep, although they are only designed to be filled to 1.5mtr, the extra height  is to ensure koi are not found on the floor!

The ponds will be filtered by extra large Bakki Showers, fed direct from the bottom drains. There will also be a simple skimmer system which will have a crud adjustable height to allow for varying water levels in the ponds. The skimmer will feed to one of my static Kaldnes vortexes by gravity and return water from this will also be pumped over the shower.

It took several days to dig out the soil for the bases, for this I used my 1 ton digger and dumper as I cannot get very large machines inside the tunnels, it seemed silly to hire one only marginally larger. Once the base was dug out as a whole it then had to be divided into individual ponds and shuttered up for pouring the concrete. This was done using a cheap laser level and 8" scaffold boards used to divide the pond bases. 

Next step was to set out the pipe work for the bottom drains, these were set into trenches dug into the clay and supported temporarily on platforms of concrete. 

For these ponds I have designed the bottom drains along the lines of those used by Japanese breeders on their koi farms.  They are basically a cone connected to the 4" pipe run, with a recess at pond floor level for a small grid to drop into. The reason for moving away from conventional domed lid drains is to stop small koi from being sucked into the drain, I can vary the grid size to suit the koi held. The down side is there is less suction to pull waste to the drain, but I can live with this.

Due to access being difficult in the polytunnel I was left with a few options of how to get the concrete into the bases of the four ponds, I chose the quickest and easiest. By pump truck, apart from the hassle of setting up the pump truck and a couple of blockages in the dry pipes it only took 20 minutes to lay and tamp each pond base.

The finished bases, if you looked at the earlier photo of the bases with bottom drain lines in, you will have noticed that I stuck temporary lids on each of the bottom drain cones, this allowed simple tamping of the concrete without having to worry about any going down the drain. After, the lid will just be smashed off. They are stuck on in such a way so they no damage will occur when breaking the lid off.