Stabilization
of Highway Cut Slope Trials using Compost and Straw
Wattle Applications
MOYIE BLUFF
PROJECT 2
Location:
Cranbrook / Moyie, British Columbia
Client:
Dawson Construction Limited
Objective:
To help
stabilize an extremely steep highway cut slope by holding
the weathered, compacted glacial till on the slope using
soil bioengineering techniques.
The
Moyie Bluff trial sites are located
on highway 95 near the town of Cranbrook, in southeast
British Columbia. These sites were part of a major highway
widening project.
Trials
were conducted on two sites (1 and 2). Both
sites received a combination of the following treatments:
straw wattles, brush layers, live staking, planting
of native seedlings and hydro seeding. In addition site
1 received a compost application.
These
techniques are expected to address surface erosion (rill
and gully formation) by establishing a woody tree &
shrub component, along with grasses and legumes.
The
species used in the brush layer structures consisted
of 80% black cottonwood (Populus balsamifera ssp.
trichocarpa) and 20% willow (Salix scouleriana),
harvested locally. The native seedlings consisted of
a mix of cottonwood and alder (Alnus ssp.).
Monitoring
of the sites was done in fall of 2005. Survival was found
to be very poor on Site 2; nearly all the planted vegetation
was dead. On Site 1, however, where the compost was applied,
survival was much better. Some of the cottonwood planted
in brush layers was still growing and many of the cottonwood
and alder planted as seedlings were doing relatively well.
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