DEQ completes Santosh landfill cap
The Oregon Department of Environmental
Quality (DEQ) has completed the installation
of a new state of the art landfill
cap at Santosh Landfill. The impermeable
cap prevents precipitation from coming
into contact with the waste, and
reduces the risk of groundwater contamination.
The 15-acre landfill accepted waste
from 1970 to 1983.
This year’s construction involved
regrading the landfill with about
43,000 tons of imported soil to promote
drainage. The impermeable cap is
a geocomposite clay liner, consisting
of a layer of processed clay sandwiched
between two layers of geotextile
fabric. The landfill improvements
also include a landfill gas venting
system and a storm water collection
system. The site was covered with
48,000 tons of topsoil and seeded
with native grasses. Soil and rock
for the project were obtained from
the nearby Glacier Northwest facility,
which minimized related truck traffic.
The $3.5 million dollar project was
funded by the Solid Waste Orphan
The DEQ has monitored environmental
conditions at the site since 2004,
when contaminated water was observed
leaching out of the south side of
the landfill. This portion of the
landfill was regraded and capped
in the fall of 2007 to eliminate
the most obvious leachate seeps.
A small strip of wetland adjacent
to the landfill was covered as a
result of this construction. To compensate
for this, DEQ constructed and fenced
an enhanced wetland area nearby.
About 700 native trees, shrubs and
ground cover species were planted
in the enhanced wetland area.