Constructing our wildlife pond
First, we reinforced the sitting area next to the original pond. Our yard slopes toward the house, which was a real advantage for our first pond since it made the stream look more natural. For this pond, though, that means that the lowest point is at the house, so it made the area behind the sitting area that much higher when we dug it out to be level with the lowest point.
Our main problem was to figure out how to hold back the soil next to the sitting area in a safe and inexpensive way. A regular retaining wall would have worked, but would have been much pricier.
Our solution was to use pressure-treated lumber held in place by posts set in concrete.
(Afterward, it occurred to us that we shouldn't be using treated lumber, which is treated with toxic chemicals. In this case we hope there will be no harm done. It will not be adjacent to the water, but to a mulch-covered sitting area. From now on, though, we won't be buying any of this type of lumber.)
We split the difference and reinforced the top two-thirds of the bank with treated lumber. The bottom third juts out some and is pretty solid since it's the original soil about two feet below the original surface. We're using this one-foot-wide area for planting.
(The end of the original pond is in the upper left corner of the photo. The sitting area appears—with a little imagination—to be on a bridge of land on top of one continuous body of water.)
This shows the stones supporting the bottom third of the wall— actually pieces from our neighbor's sidewalk ("urbanite") they were replacing. We filled in the spaces with sifted soil.
Protecting the edges
Another use for sifted soil: adding water to turn it into mud to cover the sharp edges of shale. Our yard has a lot of shale beneath the surface. This has been a real difficulty with both ponds. We've ended up with a lot of stone debris—but stone debris that is pretty useless for anything since it's so brittle.
The planting pocket for a water lily is at the upper left of the big hole.
The standing brick at the lower left is there to indicate the probable maximum water level. It's important to keep thinking ahead as much as possible when you're designing a pond.
We then spread the underlayment and the PVC liner. We used PVC for this pond as opposed to the EPDM 45 mil we used for the first pond. The PVC is advertised as being stronger even though it's thinner. It was more expensive so I hope they're correct.
This photo also shows the large, very deep hole in the middle that was intended to provide a place for frogs to hibernate. This was first lined, then filled in with soil so that the ultimate depth is just under two feet with a mud-filled hole in the middle.
After using a LOT of extra liner (and thus much more money) to make this deep pocket of mud, I learned that frogs don't actually bury themselves deep in the mud, so it wasn't necessary. Having a hole in the ice is necessary, though, and we've had some problems with that. We haven't been successfully overwintering frogs. One year, we experimented with leaving a PVC pipe in each pond so there is a place for air exchange. I checked it each morning and poured in some warm water if it had iced up. It didn't work, though, and our frogs didn't survive the winter.
Since the bagged stones were very dirty with who knows what kind of dirt, we decided to wash them first. We also removed any sharp pieces of stone.
We added sifted soil, some large glacier boulders for stepping stones (since I didn't have room to leave a path), and we started to add stones. We bought large flat stones to line the wall of the deep hole in the middle.
Unfortunately, the stepping stone path didn't work out. Most of the stones weren't high enough, so there isn't really any way to walk across the area. Oh, well …
Adding kitty litter
After adding soil, we added kitty litter—yes, kitty litter. Why? Because it's just pure clay. We made sure we didn't get any with deodorants etc. added. We added this to try to keep the soil in place.
Was it a good idea? Was it even necessary? We don't know yet. I thought we'd do this because that's how we had created the lily planting pocket in our original pond.
On the one hand, we're trying to create a natural pond; on the other, natural ponds develop naturally, not with a liner so I feel we can make some of these adjustments. We had to experiment since there's very little guidance available for this type of pond.
Another issue was how to deal with overflow. We're fortunate in that even though it looks like it's right against the house (and it is), this part of the house is a family room converted from a garage, so our actual basement is about 15 feet away. If the pond does overflow, it's unlikely to reach the basement.
Here's our solution. We laid some pipe at the edge of the pond in front of the door and ran it to the other side of the door sloping up. So far, it works, though it is seldom needed.
The photo shows the workings of this overflow system, but we covered with a stone, so it's generally not noticeable. It's important to have an overflow system, but the reality is that it's rare that it rains so much that the water builds up to overflow level. Keeping the shallow pond with a large surface area filled is the bigger problem.
Testing the pond
We filled the pond with water to see where the folds were going to go. We then emptied it (using the water to water our front bushes).
Here's the pond the morning after we filled it. We had to make some adjustments so that the water will move farther up the pebble beach in the upper right corner. We hoped that putting kitty litter in was a good idea—the water was still pretty murky, but it settled out.
We stuck a few plants in and a piece of driftwood just to get an idea of what it will look like. We also added a mosquito dunk. At this point—before plants and animals moved in—the mosquito dunk was indeed necessary.
We put mini sandbags (sand inside the long plastic bags our newspapers are delivered in) along the back wall for added stability and to prevent overflow. We then pulled the extra liner around the sandbags.
The day after filling the pond, a dragonfly landed on the driftwood and laid eggs!
Wildlife pond finished
Wildlife pond finished! It has functioned well as a place for dragonflies and other small creatures, including toads who use it to lay their eggs.