The worst problem you can have around your home and in the garden is bad drainage. In our segment Don discovered some wet, mouldy sand in the corner of an indoor horse arena. He investigated the problem and found that it was caused by bad drainage in a garden area immediately outside the arena.
When Don went outside the arena to check the drainage, he immediately noticed that something was wrong. This area was on two levels, divided by a low retaining wall. The base of the retaining wall was covered with moss and algae, and the soil in the upper garden bed was moist and had a stale, unpleasant odour. Although a drainage pipe was installed behind the retaining wall, the soil around the pipe outlet on the lower level was bone dry, indicating a serious drainage problem.
Don started to dig in the garden bed on the upper level. As he dug down, he noted that the soil was very wet and smelt like sulfur, or rotten egg gas. He then decided to dig behind the retaining wall and find out what was attached to the solid plastic outlet pipe running under the wall from the lower level. He carefully removed sods of grass behind the retaining wall so that the lawn could be replaced later.
Don found a layer of filter or geotextile fabric about a metre below the surface. This filter fabric was completely clogged with fine particles of soil. Beneath the fabric was a thin layer of gravel surrounding agricultural (or ag) pipe. Although this drain had been constructed in the traditional way, Don felt that the clogged filter fabric may have prevented water from getting through, and so contributed to the drainage problem. Also that not enough gravel or blue metal, which helps to filter and disperse water, had been used in the construction.
Don used a new length of agricultural pipe complete with a filter 'sock'. He was able to join the ag pipe to the existing main drainage pipe. He then backfilled with blue metal, to keep the soil well away from the ag pipe. Before replacing the grass, Don tested the new drain by running water from the hose onto the blue metal. In about 40 seconds the water started to run from the outflow pipe on the lower level.
To stop soil washing away from the roots of the grass Don placed the old geotextile fabric on top of the blue metal. He then added a thin layer of soil and replaced the sods of grass. He replaced the soil in the garden bed and dressed around the plants with horse manure, taking care not to put any manure up against the stems of the plants. Finally he cleaned the moss and algae off the retaining wall, using a diluted bleach solution applied with a long handled brush.
Agricultural pipe with a 'sock' costs about $6 per metre. It is available from hardware stores and irrigation suppliers.
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