Helen's Garden Renovation Project

After digging out the interior of the pond yesterday, today’s job was to put the liner in and fill it up with water. I had plenty of leftover liner from my other ponds to use as underlay. The instructions said I should use sand underneath the underlay but I thought that was not going to be possible for a pond with such steep edges as mine. I think it’ll be all right with just the underlay.

My liner measured 4m by 4m. That is big. I opened it out and then folded the edges towards the middle, and put it into position, then opened out the folded edges. That part was quite easy. The hard bit was trying to arrange the folds neatly. I bought a PVC liner rather than a butyl one because when I went to the garden centre, they didn’t have any butyl liner the right size. Although the PVC was much cheaper, it has the disadvantage of being more rigid than the butyl liner. The butyl liner would have been easier to arrange in folds, I think. I decided to have a rest from trying to deal with the folds, and went in and had a cup of tea. Then I decided that I needed a tuck at each vertex and went out and had another go. By then the sun had come out and the liner had softened a bit in the heat, so the job was easier.

I started filling the pond up from my water butts. I managed to get nearly up to the top before the water ran out. As I don’t want to use tap water if I can help it, I will have to wait for some rain before going any further. I also have the pleasant prospect of spending an hour at a garden centre, choosing some aquatic plants to go in them. In the meantime I pulled out some pondweed from my raised pond, rinsed the green slime off it, and gave it to the new pond to be going on with. I will let the pond settle, and then trim off the excess pond liner and bury the overhang.

Octagonal pond almost full

I think the shallow sloping areas (front and back) will encourage birds to splash around. I may glue some cobbles onto the liner on the slope. Note that I will definitely glue them on. If any loose cobbles fall in the pit in the centre they will never be seen again. I am also going to use plants around the pond to partly overlap the liner and maybe a few rocks here and there. I don’t want the shape of the pond to be concealed after all the trouble I went to to make it a regular octagon.

Yesterday I reinforced the edges of the pond by applying some mortar all around the outside edges. This seems to have done the trick – today they felt very solid. So today was the day for digging out the pond.

I decided that I would have two marginal shelves on the left and right as I looked at the pond from the kitchen window, and a gentle slope going from the near and far edges so that any visitors who don’t want to live in the pond permanently can get out. This left a section in the middle with a square cross section for me to dig out to a depth of 3 ft. So I got going.

I soon realised that while going to a 3 ft depth may be excellent from a pond ecology point of view, there were some substantial engineering and health and safety disadvantages. I made rapid progress up to about 1 foot because the soil is sandy and quite soft. After that, the rate of increase in depth of the hole slowed considerably. The deeper the hole gets, the harder it is to remove soil with a spade. I could have done with a soil removing tool like the one used by the man who replaced our lamp post last year. I began to entertain dark thoughts, such as whether my boss’s suggestion about the depth of the pond was nothing to do with the needs of the wildlife but was revenge for what I did to the academy XML census files last week. Eventually I stood in the hole and removed the subsoil in handfuls. I also had to consider what to do with the subsoil. I decided to put it in my empty bags of sand. I used 13 bags by the time I had finished. Fortunately my soil was well behaved and did not cave in. When the liner is in place, the weight of the water should hold the sides in place.

It was difficult to get the exposure right because it was quite a sunny day, but here is my best attempt at photographing the hole.

The hole

And the tape measure close up:

The depth of the hole

And here I am standing in it:

Standing in a 3 ft deep hole

If you are wondering how I managed to get the earth out of a hole of such a small cross-sectional area, I did it by repeatedly folding myself in half with straight legs and arms. I couldn’t crouch down to get the earth out because there wasn’t enough room. I decided that the blog would not be enhanced by the inclusion of a picture to demonstrate this technique. The two bits of crazy paving to the right are there in case I needed something to step onto in order to get out of the hole. Fortunately I didn’t have any trouble extricating myself.

When I had finished, I put two square plastic planters in the hole, so it wouldn’t be full of cats and foxes the next morning, and took a final picture.

The pond dug out with marginal shelves and slopy bits

I still don’t know whether digging the pond so deep was a good idea or not. Although there are shallow edges, I am worried that animals might fall in the deep bit and drown. And when the time comes to clear out the pond, I will have to get a bucket on a rope and haul it up to remove all the water. But if it really doesn’t work, I can always lift out the pond liner and fill in the hole a bit. As for what to do about the subsoil, I have a cunning plan. I intend to mix it half and half with compost and put it into the lawn area. I think that overall that should be equivalent to top soil, and will mean that I don’t have to buy as much top soil when it’s finished.

After destroying the first version of the octagonal pond, I have had to wait for the right weather and for the exams to be mostly over. A week ago these conditions were met and I made a start on the second version. This time I used tape measures, bits of string, planks and a large set square, and I was pleased to find that I managed a layout that looked near enough right.

Edging under construction

I put the four sides which were parallel or perpendicular to the patio edge in first, and then added the diagonal edges. The diagonal edges were easy because they had to fit between the other edges. I used two short pieces of wood to line them up. Then I filled in all the gaps, and I got a pond edging that lines up with the greenhouse:

Octagonal pond in front of octagonal greenhouse

The edging is not perfectly level, but the amount it is out by is the width of a single thickness of pond liner, which I think will be good enough, given that the liner will inevitably have folds in it. And if you view the pond from a diagonal, it STILL looks like a regular octagon. Amazing.

Octagonal pond viewed from a diagonal

I now need to build up some mortar around the bases of the bricks to make them more secure, so that when I trip over them they are less likely to be dislodged. And then there is the small detail of digging out the pond. My boss said that he dug his pond out to 2 feet deep and afterwards regretted not digging it deeper, to 3 feet. I thought that if I dug my pond out to 3 feet, my back might regret it later. But then my boss’s specialist subject is ecological biology and creatures that live in ponds so his opinion is probably worth taking some notice of. And I like a challenge…