Now you have done your homework and considered all the options. The excavation area has been marked and adjustments have been made. Adjustments always happen, don’t worry. It is time to bring the spades or if you can get it to the site, an excavator. For various reasons, a pond should be as deep as possible in South Africa. The reason may be from ensuring temperature stability, protection against extreme climate and larger volume of water to keep the fish in. There are also different views on the effect of pond depth on the development of the fish, but the advantages of a deep pond are so obvious that it makes the whole debate about development of Koi in deep or shallow ponds obsolete.
My advice is always to design the pond as deep as practically possible. The surface area of the pond will determine the depth because a balance should be maintained. It must be considered that a small very deep pond may need extra aeration to maintain the desired dissolved oxygen content in the water. Dig the sides vertical and support the excavation to prevent cave-in accidents. Shaping a pond with sloping sides waste a lot of potential water volume and provides a nice ramp for fish to jump out. It also creates an entrance to the pond for predators and the family dog. The depth of the excavation will depend on your decision whether the pond sides should be level with the ground or raised.
At this stage you should not excavate the filter area. This should be done after the height of the water level has been determined and you know the exact depth required for the filter base. If the pond is partly or fully above ground, the filter base may not be much below ground level.
Remember to excavate about 30+ cm deeper than planned to provide for the concrete base of the pond. When the desired level has been reached, it will be necessary to shape the bottom to accommodate the slope towards the bottom drains and to compact the loose soil. Depending on the type of bottom drain that will be installed, trenches can now be dug to lay the bottom drain pipes. These should be wide enough to allow for the pipe-work to be encased in concrete before the pond base is cast. If you have decided on a “hanging pond floor”, the foundations should be dug out. A hanging pond floor is where you build the pond sides on a foundation and then cast the pond floor. Different pond bases will be discussed in more detail later under the Concrete Base.
By now you have realised that you did not allow adequate space for the excavated soil to be stored. Phone a company to remove the access soil and mark it as expenditure not budgeted for.
Updated 8 February 2009
Last Updated on Sunday, 08 February 2009 21:23