Restoring Subsurface Drain Performance

The restoration of drain performance is of vital importance in preventing soil salinity buildup. Consequently, malfunctions must be recognized quickly using various diagnostic techniques. Two types of obstructions have been observed. These are: (1) physical obstructions such as silt and roots; and (2) mineral deposits. Mineral deposits may be removed by injecting a 2% mixture, by weight, of SO₂ gas and water after flushing the system with water to remove loose materials. A chemical method of removing gypsum is not available. High pressure water jets are effective in removing silt from tile drains. They are also effective in removing small roots and gypsum deposits in the form of small crystals, but are ineffective if the deposit is in the large dense crystal form. High pressure jetting equipment has been used successfully on a commercial basis in Imperial Valley. Long flexible rotating rods with cutting blades are most effective for removing roots, especially the large roots from the drainage line.