Subsurface drain installation methods - Assessing their functionality with water table and drain outflow measurements

The aim of this study is to figure out the functionality of drains installed with trenchless and trenching drainage machines, and to give guidelines in the use of drainage machines in different conditions. Performance of installation methods were investigated in a field experiment. Soil type in the drainage depth varies between loam, sandy loam and clay loam. The field was flat (slope 0.16%). Groundwater levels were measured automatically and manually from observation pipes installed at distances of 0.2, 0.6, 2.5 and 7.5 m from the middle drain in each section. Drain outflow was measured from two collector pipes installed with each machine. According to results, the trenchless method had slightly higher water tables in all distances of the drain by average. Differences in the water table were higher in wet seasons, when snow melting and high precipitation occurred. The trenchless machine had higher variation in groundwater levels. Drain outflow was 10% higher with the trenching method. The outflow was significantly higher in rainy seasons for short periods of time, when groundwater was up. During the short research period, the trenching method was slightly more effective. Research will continue until the end of 2016.