Introducing: Full Moon Dam. Created as part of the Earthworks course that ran from 24 – 28 September, the process of digging this dam displayed the challenges of creating a dam in shale, and took student through the whole process, from design through dig to rehabilitation.
The property has very little clay in the ground, but lots of shale, which posed a problem in creating a dam that holds water. It was the first hurdle to overcome, but we found out that someone we know has clay on their nearby property, so we organised a trade with them to get some clay.
The second hurdle was the fact that there were a number of fruit trees which had to be relocated. They were gently dug out and put into a temporary spot close by, ready to be moved to their permanent home after the dam was finished.
Tom removed the top soil in the area with his excavator and piled it up close by so that it could be spread out over the dam wall and surrounds and planted into as part of the rehabilitation and erosion prevention process.
The large excavator came in and dug the hole, then he pulled the clay (which was dug up at the other property and trucked over) into the hole and mixed it with dirt from the walls. This was done while Tom and the students were watering the walls, to ensure the clay would combine and stick to the surrounding material.
The excavator drove into and out of the dam a number of times to compact the walls, after which Tom took the four wheel drive into it and compacted it some more by driving in and out.
Once it was compacted enough some topsoil was spread out over the wall and surrounding area, and Tom dug in 2 stumps which will hold the jetty. He then started filling the dam with water to check its water holding capability. Better to find out earlier rather than later whether it leaks or not!
Whilst the dam was filling up, rehabilitation was begun on the dam walls. Among seeds and plants planted are pigeon pea, pinto peanut, cowpea and japanese millet.
After filling the dam it dropped around 25mm every 24 hours. The drop in level may be due to soaking of the surrounding soil and nothing to worry about. If it does drop more, we will need to look into methods of getting the dam wall to bond.
Tom has had his first swim already, and enjoyed it immensely, despite the coolness of the water! The dam will function as a swimming pool for students in future courses and will also have a variety of water life in it. Water chestnuts are already residing on the edges of the dam and we look forward to adding some fish and other water plants, to ensure the dam will maintain a healthy and clean environment.
Tom has also dug part of the swale system which will connect to the dam. The part of the swale leading up to the dam will function as a filtering system, with reed beds that will stop mud, nutrients and runoff running into the dam. This way we hope to stop the dam from becoming dirty and muddied up, so that we can keep enjoying clear and clean water.
The reason the dam was named Full Moon Dam, was that on the first night we had water in it, the full moon was reflected. The dam itself is also perfectly round, just like the full moon. The reflected light from the moon actually comes into the house through the windows, creating a beautiful ambience.