ABSTRACT
This chapter describes some less commonly used dewatering and groundwater control systems, and outlines conditions appropriate to their use. The ejector well system is suitable for pore water pressure reduction projects in low-permeability soils such as very silty sands, silts or clays with permeable fabric. An ejector is a type of jet pump. Several different designs of ejectors are available, each having different characteristics. The installation and connection of twin-pipe ejectors suspended in a well involves rather simpler plumbing than for single-pipe designs; this can make the twin-pipe type more suitable for use in localities where skilled labour is scarce, and it is desired to keep dewatering equipment as simple as is practicable. Horizontal Directionally Drilled techniques used for installation of dewatering wells have been developed from techniques originally developed to allow oil and gas pipelines to be drilled beneath obstacles such as roads and rivers.
