Selection of drainage and evaluation used filter media

The feature of running the suffosion of sand grounds in the top five-meter soil-ground layer where drainage is constructed on the basis of existing normative documents and granulometric composition of filter material was determined with reports. The actual and report contents of the filter differ sharply. Large particles (40% by weight) of more than 20 mm should be sorted out from the sand-gravel ground to be used for construction of drainage.