Reducing petroleum hydrocarbon contaminants in groundwater
By Phillip Lowery
Excavation activities at a former service station.
Petroleum hydrocarbons have
become a nuisance at many
sites across Canada. Leaking
underground storage tanks
(USTs) have caused multiple releases
of volatile petroleum hydrocarbons
(VPHs) and light extractable petroleum
hydrocarbons (LEPHs) to the soil
and water table. Many in situ remedial
options, such as Air Sparging/Soil
Vapour Extraction and Pump and
Treat, have attempted to reduce high
levels of these contaminants at the cost
of millions of dollars over many years.
Oxygen Release Compound
(ORC®), an in situ technology, has
been successfully applied at a former
service station/car dealership in the
greater Vancouver area. The application
of this safe and easy to handle
powder has reduced high concentrations
of VPH, LEPH, and naphthalene
since its injection in October 2003.
A preliminary site investigation was
conducted to assess possible groundwater
and soil contamination originating
from eight former underground
storage tanks historically used by both
the service station and dealership. The
USTs included four gasoline USTs,
two bulk oil USTs, one diesel UST,
and one waste oil UST. Possible soil
and groundwater contamination was
expected, especially high levels of
VPH and LEPH. Currently there is no
UST or pump island.
Following the completion of a
detailed site investigation, soil contamination was found within and adjacent
to the former gasoline UST basin.
Based on the results of multiple borehole
samples, the area of concern was
delineated to include the former gasoline
USTs as well as the pump island.
A total of 1,300 m3 was identified as
contaminated soil while 1,350 m3 was
estimated as contaminated groundwater.
As expected, soil and groundwater
contamination included VPHs (13,000
ug/L), LEPHs (2,600 ug/L) and, to a
lesser extent, naphthalene (240 ug/L).
Remediation goals were established
based on the standards set through the
Contaminated Sites Regulation of
British Columbia, specifically Commercial
Land use for soil and Aquatic
Life standards for groundwater.
Oxygen Release Compound.
Remedial action was initiated
through complete excavation of the
1,300 m3 of contaminated soil. An in
situ remediation program, using ORC,
was developed to address the contaminated
groundwater. ORC, manufactured
by Regenesis (San Clemente,
California, USA), is a magnesium-based
product designed to release pure
oxygen upon hydration in the subsurface.
The rate of degradation is then
accelerated to treat contaminated
groundwater through the removal of
various compounds, including petroleum
hydrocarbons.
In October 2003, a total of 1,350
pounds of ORC was injected via direct-push
technology in a grid formation
over the plume as well as in the backfill
to the excavated area. Decreasing
trends began shortly after injection and
within one year of application VPH and
LEPH concentrations had been reduced
by up to 80% in the source
area. With the exception of one well,
VPH concentrations had reached below
groundwater standards downgradient
of the source area. Naphthalene reduction
included an 85% decrease in two
downgradient wells and a reduction to
below 100 ug/L in all wells. Currently,
five wells have sampled below naphthalene
standards (10 ug/L).
ORC typically delivers oxygen to
the subsurface for periods of up to 12
months. In order to continue the reducing
trends seen in VPH, LEPH, and
naphthalene, a second injection using
ORC Advanced™ was completed in
December 2004. This new formulation
of ORC is a calcium oxyhydroxide
based material that offers more oxygen
per pound than regular ORC. A total of
500 pounds was used to target the
source area and continue reductions
over the following year. Based on the
current contaminant reduction trends,
ORC Advanced is expected to meet the
cleanup goals and expedite site closure.
The increased rate of enhanced
bioremediation allowed significant
reductions throughout the plume within
one year of injection. The total cost
for ORC and ORC Advanced product
was $23,955. To date, a grand total of
approximately $200,000 has been
spent for excavation, ORC and ORC
Advanced application, and associated
remediation activities.
Phillip Lowery, of Next Envionmental
Inc. is Project Manager
for this site.
Contact: sdobyns@regenesis.com
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