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Additional Drainage Control

There are a number of additional drainage control techniques that can be applied to some sites in cases where there is an unacceptably high level of risk to existing structures and there are limited alternatives available to your slope. Each technique requires a geotechnical engineering evaluation and involves using specialized construction equipment and installation practices. Generally, these techniques are very expensive to implement and are intrusive to slope soils and vegetative cover. Most importantly these drainage control alternatives can be devastating to slope stability if poorly applied or constructed.

• Horizontal Drains - Horizontal drains are small diameter wells drilled almost horizontally into a slope face to remove groundwater and seepage before discharging onto the slope face. These drains are primarily used for stabilizing slopes although they can be used in emergency situations to provide immediate relief of adverse groundwater and seepage on problem slopes. Installation of wells requires that a construction platform is cut into the slope.
  
• Well systems (vertical wells & relief wells) - Well systems are used for improving groundwater conditions in troublesome slopes. Wells are typically drilled vertically into a slope and provided with a discharge pipe at the bottom of the well which drains water freely to a collection pipe or pervious soil material. Well systems require multiple installation in an area to effectively lower the groundwater elevation. In extreme cases, pumps are included in the design layout. The term "chimney" drain is sometimes misapplied to coastal slope drain design. Traditionally, its use is confined to earth dam construction.
• Drainage Blanket - Drainage blanket is a layer of free draining granular material placed on the face of a slope to help stabilize shallow soils and reduce erosion. Blankets should be specified by geotechnical engineer to help avoid increasing your stability problems.

	Applicability	Compatibility

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