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
- 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
- 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.