Live
Pole Drain Systems
SHEEP
CREEK LIVE POLE DRAIN SYSTEM
Location:
Salmo,
British Columbia, along the Sheep Creek Road.
Client:
Ministry
of Transportation and Highways (MOTH)
Objective:
To
restore stability of the slide site using soil bioengineering
structures and provide drainage of surface and subsurface
seepage water using live pole drain systems.
The
debris slide and earth flow at the Sheep Creek failure
site originally occurred between the fall of 1998 and
the spring of 1999.
Gradients
on the slide face range from 80 to 150% and from 30
to 60% on the debris at the toe of the slide. The material
is primarily glacio-lacustrine inbedded silt and sand
with some clay. The glacio-lacustrine materials are
overlain by glaciofluvial sand and gravel. The glaciofluvial
materials are dry and well to rapidly drained. The glacio-lacustrine
materials are poorly drained and include extensive areas
of seepage. The water table is perched on silt and clay
layers in a number of locations.
Live
pole drain (LPD) systems, which included lateral drain
fascines, were installed in four natural drainage /
seepage channels within the slope failure area in the
spring of 2001 (other structures installed at the same
time are discussed in the Sheep
Creek project page). The central pole drains
were constructed using cylindrical bundles of live cuttings
approximately 30 cm in diameter and using the lateral
drain fascines bundles of approximately 15 to 20 cm
in diameter. The live cuttings used consisted of a mix
of Willow species (Salix bebbiana / scouleriana
/ exigua), Black Cottonwood (Populus balsamifera
ssp. trichocarpa), and Red-Osier Dogwood (Cornus
stolonifera). The structures were secured on the
slope using steel “T” re-bars.
The
site was monitored from 2003 to 2005. The site showed
fully functioning live pole drain systems, draining
surface & subsurface seepage water into the ditch
line adjacent to the road and good overall growth of
the establishing vegetation. |
