Doing our sums.

Before buying the butyl it was necessary to calculate the amount of liner we needed, which involved knowing the width, length and maximum depth of each pond. Then we had to multiply the length times the width, with twice the maximum depth added onto each dimension. We also added an allowance for an overlap around the edges, to create small wetland areas around parts of each pond. Lastly, there was a further allowance made for the soil which we would put on top of the butyl to form the base of the ponds. This would help naturalise the ponds for plants and wildlife.

Once we had the butyl to hand, the next step was best done by at least two people. The idea was to unfold the liner over each pond to position it centrally. My husband and Number One Son gathered large stones from our boulder mountain to place on top of the butyl around one side of the pond to stop movement in the liner. Gradually they worked their way around the pond, adding more boulders as required.

After this stage, my husband went right down inside each pond, in his stocking soles, making necessary adjustments to the liner and creating overlaps around corners and on the shelves. It was a fairly tricky and time-consuming job, but a vital one before the ponds could be filled.