So far we have the watershed side of the pond finished, the bowl or dug out area to hold the water in the pond and now we need to have a way for the excess water leave the pond in controlled way.
There are two ways to get the excess water out of the pond safely. One is an overflow pipe (trickle tube) and the other is the emergency spill way. This pipe will keep the pond water level at the height it is set at. And take care of extra rain run off over filling the pond.
The over flow pipe can be done after the pond is done but before the water fills in the pond. This is the easiest way to get the pipe in. There are times that a pond would need to be drained down, repairs if a leak should occur and to help eliminate an over population of unwanted fish. This would be a drain pipe and combined with the over flow pipe. Having a bottom drain will need to be installed before building the dam, then must be watched that it’s not dug up or run over by the dozer. 🙁
At WhatPond we went for the over flow pipe but also made it a drain. The drain would bring the pond water level down 5 feet. Positioned the backhoe on top of the dam and dug a ditch 5 feet down starting at the pond side out to the front of the dam. The ditch should be level to a gradual slope, sloping down and away from the pond. What kind of pipe? The best is plastic with rubber seals such as SDR 35. Using steel will lead to problems later once the steel rusts away. When running the pipe through the dam anti seep collars should be used. Here’s the deal, back to the mashed potatoes clumped on the plate.
Get a straw and pack it in to the pile of mashed potatoes leaving the ends stick out. At first the potatoes
have a little moisture and will adhere to the straw. After a day or so the potatoes will dry out leaving a small space around the straw. This is how water will get out.
The anti seep collar is a tight water seal around the pipe and extends out from the diameter of the pipe. Then the water would travel along the pipe it will
be stopped by this seal and diverted by the collar. Like the straw in the mashed potatoes, as an example of a anti seep collar take masking tape and wrap the straw in two place until it is twice the diameter
of the straw. Now put the straw back in the potatoes and see that it will not slide out as easy.
When installing the pipe there is the horizontal pipe goes through the dam and the vertical is in the pond water. At the intersection of these two pipes two things can happen, one a 90 degree elbow can be installed or a “tee” can be installed leaving an option for a gate valve. This will give the option of draining the pond down to the level of the ditch.
Installing the pipe. Be sure to set the elbow or tee into the dam far enough that it will be buried in the dam. This will keep the vertical pipe up right.
Back filling the ditch and compacting is very important. The use of a tamper is the best way to get the ditch packed in. Rent one or find some one that will come do it for you. There is no other way to pack the ditch in as tight as the tamper. This is going through the dam so it needs to be compacted.
We seem to have run out of space so next week we will get into the spill way.