How to Construct a Concrete Pond
Estmating the materils
Excavating
>To drain or not to drain
Placing the forms
Working with Concrete
Pouring the Floor
Setting
Fountains and Spouts
Unfortunately, you may see the drawback of drainless construction all too graphically after the first exceptionally heavy rainstorm fills the pond to overflowing. Probably you will lose some gold1ish, and the excess water will make a mess of the whole area.
A dry well installed within a few feet of the pond will take care of overflow through any season of normally heavy rainfall. Excavate a cubic yard of earth, making sure to excavate lower than the pond, as illustrated. Fill the excavation to within a few inches of the top with rocks or cinders, and tamp them down. Run an overflow pipe from the pond to the dry well as shown, and cover the well, first with planking, then earth, and finally with a layer of sod.
Far more practical, if you have access to some gutter, sewer outlet, or lower point of ground into which the overf1ow pipe can empty, are the various drainage arrangements shown in Drawing 5. Use galvanized iron pipe, 1 1/2 or 2 inches in diameter, for the drainage system. Set the coupling, of brass, which will not rust, into the floor of the pond. The pond will drain more efficiently if the coupling is set an inch or so below the surface of the floor so that the surrounding area will slope down to it.
If you are building your pond in soft ground which requires both outside and inside forms, the outside structure need be constructed only tight enough to hold back the sides of the excavation. Two-by-four stakes driven into the ground around the perimeter will do nicely as supports. To these, you can nail the planking which comprises the outer form. This form need not be removed after the pond is finished.
The inner form requires neater work, for the outside of this form will mold the inside of the pond shell and the surface will show. One-inch lumber, new or used, is best. Forms made of thinner wood will bulge.
with the weight of the concrete. Wood thicker than an inch makes for heavy, clumsy handling. Even with sturdy forms of 1-inch lumber, guard against bulging by using two-by-four cross-braces every 3 or 4 feet along the length of the pond.
Build the form as you would build a bottomless box. Remember that for a pond which is to have a water depth of 2 feet, the form will have to have a depth of 2 feet and 2 inches. When the pond is filled to a 2-foot depth, the water won't be lapping over the brim; there will be a 2-inch margin of dry wall extending above water level. Be sure to set the form so that the rim of the pond will be slightly above ground level (up to an inch) to prevent seepage of surface water.
If you plan an ornamental rim for the pond, perhaps a surfacing of brick or flagstone, you still extend the concrete walls to a point just above ground level, a half inch or so. Remember that with any kind of material, it is extremely hard to get a watertight seal between it and the rim of the pond. Say, for example, that you have a brickwork rim. If you fill the pond to the top of the bricks, pond water will leak out. If the brick rim is below or at ground level, surface water will leak in.
When the inner form is completed, square off each corner and nail a temporary brace across it to hold it true.