Soil permeability test - percolation test

The easiest method of managing water purified from a wastewater treatment plant or an emergency overflow from a rainwater tank is drainage of water in the ground on the investment site. However, in order for the infiltration system to function properly, the geological properties of the soil must be examined. In order to determine the soil permeability, i.e. the soil's ability to seep water, the so-called percolation test. The percolation test is a soil test that determines the possibility of using an infiltration system or a given type of sewage treatment plant.

The preliminary percolation test is performed as follows:

1. A test trench should be made to the depth at which the designed drainage will be located.
2. Then a 300 x 300 and 150 mm deep excavation should be made in the bottom. All loose soil should be removed from the trench. The walls of the trench should not be even or smooth. The width at the top of the trench should not be greater than 30 cm, and the width of the bottom part should be greater than 10 cm.
3. Before starting the measurement, the pit should be moistened. The amount of water required for this purpose depends on the type of soil and the season. The test trench should be flooded with water and kept in this state for 4-24 hours until the water in the trench is soaked in within less than 10 minutes.
4. Pour 12.5 liters of water into the hole. The water depth in the hole  will then be approximately 139 mm. At this point, start the stopwatch and measure the time t (until the water is completely soaked in) in the side walls and the bottom of the hole. You can wait until the water is completely absorbed in, or if this time is long, you can use the measured time for the water  to fall down by 10 mm in the hole. The soil permeability class is determined on the basis of the soil filtration coefficient obtained from the measured water infiltration time.
5. In order to verify the correctness of the measurement and eliminate any error, make at least 3 measurements and calculate the average from them. The obtained result can be compared with the table below.
   
   

B, C and D soil are suitable for underground drainage of sewage. Class A primers require the use of a supporting layer of class C soil.

Soils A, B, C and D are suitable for the distribution of rainwater.

Table: Soil classification in relation to the percolation test