design | dəˈzīn |
1 a plan or drawing produced to show the look and function or workings of a building, garment, or other object before it is built or made
2 purpose, planning, or intention that exists or is thought to exist behind an action, fact, or material object
1 decide upon the look and functioning of (a building, garment, or other object), typically by making a detailed drawing of it
2 do or plan (something) with a specific purpose or intention in mind

Thursday, June 26, 2008

The Hidden Bog Garden (part 1)

A few years ago I became intrigued about bog gardens in that they allow you to grow exotic plants that one would normally only find in a pond. As bogs are mud and not water they do not carry with them drowning hazards for children and animals nor do they become breeding grounds for mosquitoes (if the bog garden is properly designed and maintained).

I built my first bog garden in Southern California and it turned out great. However before it could really take off we moved to Northern California. The good news is that my new home had a perfect place in the side yard to build a bog garden that would not only contain the bog but also serve as a nice focal point in the yard. However along the way in building the blog my wife introduced a new wrinkle when she said, "That would be a perfect place for a fountain."

As such, I've designed and built a fountain that sits within a bog garden. I'm no expert on these types of designs but I believe this brings a number of advantages:
  1. Overfill and Overspray - the beauty of a fountain within the center of a bog is that any overspray from the fountain or slight overfilling will simply go into the bog.
  2. Irrigation - even though I'm in Northern California, my particular region is rather dry and I have to irrigate my bog to keep it moist. Thus I was already running irrigation to the bog so to spit the line to fill the fountain wasn't much more work.
  3. Sound - in addition to the cool plants you can grow in a bog I like the added mistique of the sound of water flowing in a fountain.
OK, so maybe these advantages don't justify the work involved in building a fountain within a bog garden but it was enough for me to expand the project. What I wanted to create is a non-exposed water collection container (where the pump sits) and the appearance of water pouring into the bog.

One of the interesting design aspects of a bog garden is that your ground over (e.g. bark or rocks) can blend in seamlessly with the ground surrounding the bog. When complete this hides the boundaries of the bog and no one will even know that there is a bog garden there (other than the different style of plants that grow within). Thus the bog can make people ask, "How is it possible that those plants are growing in regular soil?"

Forming the Bog
In this I dug out the bog garden perimeter by removing 2 feet of soil (2.5' is recommended but I live in a clay soil area and there is a limit to how much digging and hauling of compact heavy soil I'll do). In the center of the bog I dug rectangular shovel wide trench 6" deeper where the fountain basin would sit. My main reason for doing this is to anchor the resulting concrete basin in place.

When finished the top of the fountain basin will be flush with the ground. This is keeping with my design that everything is below ground and one can't tell where the bog or fountain begins or ends. The nice thing about this approach is that you don't have to be an expert mason when building and pouring your fountain basin. I then cut plywood planks to frame the outside of the basin and another box for the inside.

What you're doing at this stage is building a form for the concrete to rest in while it cures. Wet concrete has the consistency of oatmeal that has set out for too long. It is moist enough that it will form itself into any form it is placed but it isn't wet enough that it seeps out of small cracks or holes. Thus the goal here is to build a temporary form for the concrete to sit in until it is hard enough to remove the form.

Visually imagine that you're building a box with no top or bottom. One box for the outside walls and another smaller box for the inside walls. The important trick here is to build the frame so that it can be pulled apart after the concrete dries/cures. Once the concrete hardens you won't be able to get to anything covered by the concrete (e.g. screws or nails). So build your frame with an awareness of how you'll pull it off of the form once the concrete hardens.

I then covered the entire bog with a pond liner. This is clearly the most expensive single construction material you'll purchase for this project. Stop by your local hardware supply store and see what sizes and prices they have for pond liners before designing your bog garden. You can glue multiple pond liners together for particularly large or odd shaped bog gardens (even though bog gardens do naturally drain into the underlying soil via holes placed in the liner you must glue overlapping seams or too much water will escape).

Pouring the Basin
The next step was to set the outer frame in place and pour in the foundation for the basin. The design for my fountain involves automatic filling (I tied mine into my irrigation) and the water exiting the basin via a 3/4" pipe. As such I designed my frame form with openings for these two pipes so that all of the water management was underground within the concrete basin itself. I used regular concrete but if I were to do this project again I would mix in a small portion of plastic cement into the mix for better water retention.

After pouring the foundation (8" deep) I inserted the inner frame and started pouring the side walls. The walls of my fountain basin are about 8" wide which had more to do with erring on the side of simple frame construction rather than any hard facts about how thick the walls need to be. Make sure to get enough concrete to do the job because those short trips to pick up a few more bags of concrete can present leaking problems where a new pour is placed over an existing.

Once the concrete basin cured I removed the frames and tied in PVC tubing to the exit pipe via a T connection. From this I ran 3/4" PVC pipe around the basin and tied it back into the other end of the T connection (a single continuous loop). At various points along the route I installed additional T connections with threaded openings pointing up. These threaded connections hold the copper tubing in which the water will flow out of the fountain. Similarly I connected the other PVC pipe to my irrigation system.

Building the Fountain
My aim was to build a whimsical fountain consisting of copper tubes that took water from the underground basin up and through multiple pipes poured the water back into the basin. I knew that if I simply took copper tubing and ran water through it that the sound would be too loud and it wouldn't be much fun. And I wanted the design to have a purpose for existing in a garden.

I started with 1/2" copper pipe and started by soldering threaded connections onto one end and a cap onto the other.

Each 10' copper pipe was then free form bent into random designs using a pipe bender. You can get a pipe bender at your local hardware store. Make sure to get one for the diameter of pipe you're bending as this will give you a much smoother curve with fewer bends (e.g. if you applied pressure to two ends of the pipe you would simply bend it rather than forming a curve).

If you don't know how or have access to someone who can weld copper then you'll want to skip the next step. Someone skilled at brazing might be able to make the connections but if you don't succeed you'll have holes in your tubing that under pressure will squirt water where you don't want it to go (e.g. across your yard).

I then drilled holes into the pipe and welded on a small diameter copper tubing. This tubing is available from your local hardware supply store. You'll recognize it as the copper tubing that runs to your water inlet on a refrigerator ice machine. The flexible nature of this copper tubing allows you to move, twist and contort it into a variety of positions for a cool look and to direct the water where you want it to land.

After building each fountain piece (I built three in the shape of plants with a large daddy, medium mommy and small baby) I carefully turned them into the threaded PVC "T" connections and supported each one by hammering in rebar and wrapping copper wire around the pipe. The PVC threads are easily damaged by the harder copper threads so be really careful when screwing them in.

Once the fountain pieces were secured and plumbed it was time to start filling in the blog. I chose a mixture of peat moss, top soil and sand.

About 2/3 of the way in filling in the bog I snaked a soaker hose throughout the blog after attaching it to my irrigation inlet. This will soak the blog slowly each time I turn on the irrigation for the pond/bog valve.

Once the fill for the bog was complete I topped the surface with bark to match the surrounding garden. You can also see my first bog plant behind the fountain.

Part II of this post will include adding decorative rock around and in the bog to finish off the illusion of a hidden bog and fountain.

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