The study examines the effect of lime admixture to trench backfill on the functioning of tile drainage after almost 28 years of operation. The hydrosystems efficiency examination was performed at the test site in Kalnujai, Raseiniai District, where filtering capacity of drainage trench backfill had been improved by lime admixture. When analysing the maximum drainage discharge per unit length at the control drainage systems as of spring and autumn of 2016, as well as the drainage discharge per unit length as of spring and autumn in the drainage, where the trench backfill filtering capacity had been improved with lime admixture, correspondingly better results were obtained. When evaluating the drainage systems efficiency indicators as of 2003, 2012 and 2016 with the 95 % reliability, it can be stated that the efficiency of drainage, where the filtering capacity has been improved with lime admixtures, remained virtually unchanged after almost 28 years of operation.

DOI: https://doi.org/10.3846/enviro.2017.081