Elevated groundwater levels or pore pressures are often an important contributory factor in many slope stability problems. WJ has a range of specialist solutions for reducing groundwater levels in unstable slopes, including siphon drains and electro-pneumatic pumps. Siphon drains require no power, simply relying on gravity and a siphon action, to remove the water from the wells. Note that the operating depth of a siphon is limited. Where the water bearing horizon is deeper, electro-pneumatic pumps can be used in the wells. These are driven by compressed air, and can be used in low flow situations where a traditional electric pump would not be suitable.