In 1999 roadways in four north east Edmonton neighbourhoods began to show significant
structural failures earlier than expected. As a result of continued roadway failures a study was
carried out by the City of Edmonton Geotechnical Section of Engineering Services in August
2002 to identify the issue and its extent. The original study and a successive study carried out
by Golder Associates in 2005 revealed that water was softening the subgrade soils causing
these failures to occur. The issues include subgrade soils that were susceptible to water
softening, additional surface drainage from private sump pumps and poor subgrade drainage.
With this information, the City developed several options for remediation of the failed roadways
as well as to reduce the availability of water to the subgrade soils. The plan chosen involved full
reconstruction of the roadway and installation of edge (periphery) drains. The new roadway
cross section consisted of, non-woven geotextile, installation of 200mm diameter perforated
PVC lateral drains along curbs on both sides of the road connected to the stormwater system,
recycled 63mm granular base, geogrid, virgin granular base course and asphalt concrete. In
2006 the first project with sub-drains was constructed and consisted of approximately 550m of
roadway with a cost of approximately $1.5 million.
Over the past ten years the treatment plan has shown to be working to address the issues and
the City currently has two annual contracts each completing approximately 1,300 to 1,400m of
roadway reconstruction at a cost of approximately $3.0 million dollars per year. In the past ten
years the City has completed approximately 14 km of roadways within the neighbourhoods that
were part of the original study and has locations for the next three years in place. Many
construction techniques have been learned including how to work around utilities, development
of drain wells and maintaining access for residents.
Late 2016 additional neighbourhoods were starting to show distresses similar to those reviewed
in the study. As such, in 2017 neighbourhoods outside of the original study area will be
reconstructed and others that are starting to show earlier signs of similar failures will be
monitored regularly through visual inspections and structural testing.
