Types of horizontal wells include both trenched and directionally drilled, with trenched wells involving simultaneous borehole advancement and casing/screen and backfill installation (in a larger diameter boring) and directionally drilled wells involves a smaller borehole with well installation subsequent to the completion of drilling activities.
Reported advantages of horizontal wells are related to the fact that their long horizontal screens contact a larger area of contaminated media, and so may more effectively transmit additives associated with remedial activities (amendments, air, surfactant s, etc.). In addition, the configuration of these wells is more consistent with natural conditions, since groundwater transmissivity is generally greater in the horizontal, rather than the vertical direction. This may allow more efficient recovery of gr oundwater and/or vapors via horizontal wells. Directionally drilled horizontal wells can be installed in areas with subsurface obstructions (e.g., vertical wells, utility lines) and can be used beneath surface obstructions such as buildings, lagoons, wet lands, etc. Disadvantages cited include the limited depths to which these wells can be installed and the lack of drilling contractors experienced in horizontal techniques.