Drainage Excavation Services in Canberra

Drainage problems tend to show up slowly, then get worse each wet season. Watch for:

• Water lying against walls, paths or fences for hours after rain.
• A lawn that stays muddy or spongy long after the weather clears.
• Garden beds where plants yellow or stall because the roots sit in water.
• Soil washing down a slope or out from under paving.
• Damp, leaning or bulging sections in a retaining wall.

Heavy ground makes all of this more likely. Our article on clay soil drainage in Belconnen explains why clay holds water at the surface.

Subsoil and French drains

Agricultural drains, usually called ag drains, are slotted pipes laid in a gravel-filled trench that collect water from below the surface. A French drain uses the same idea to catch surface water as well, with the pipe often wrapped in geotextile fabric so silt cannot clog it. Both are laid on a fall to an outlet.

Surface and channel drains

Along the edge of a patio, driveway or path, a channel drain (a long, narrow grate) catches runoff from the hard surface before it pools. Where water gathers in one low spot, a pit collects it and feeds the drain line.

Stormwater pipework

Rain from the roof and paved areas can be piped underground to an approved discharge point instead of spilling across the yard.

Regrading the surface

Sometimes the ground falls the wrong way. Surface regrading reshapes the yard so rain runs away from the building instead of towards it.

Whatever the method, water is run through a new drain to check it flows before the trench is backfilled.

Drainage excavation services often put trenches close to pipes, cables and footings, so the ground is checked before any digging. WorkSafe ACT advises a site investigation before excavating to establish the soil type, the water table, any risk of flooding and the location of underground services such as gas, electricity and sewers. It also treats any trench dug to 1.5 metres or deeper as high risk construction work, which needs a safe work method statement.

Where the collected water ends up decides the route of the trench, so the outlet point is settled before digging starts.

Ground drainage and roof drainage work together. Overflowing gutters dump water where the soil is already wet, so a new drain can be undone by a blocked downpipe. Our article on roof maintenance and drainage covers how the two connect in Canberra weather.

Behind a retaining wall, trapped water builds pressure until the wall bows or cracks. Gravel backfill, a subsoil drain along the base and weep holes let it escape, and they are easiest to get right while the wall is being built.