operation of the infiltration gallery will be based
couplings in the irrigation lines, the center of the
on continued monitoring.
site was more heavily treated than the edges.
The greatest operational problem that we
encountered in the landfarm so far is the man-
Recirculating leachbed
We encountered three problems during the
agement of excessive soil moisture. Spring snow
brief operation of the leachbed. First, the air
removal is the only way of limiting water input
from precipitation. High soil-moisture content
manifold floated to the surface. This should be
during the early summer may not allow tillage,
anchored using cables and "deadmen" in future
shortening an already brief operating season.
installations. Second, "piping" of water was ob-
Evaporation of excess moisture may be enhanced
served in the soils immediately above the water
by pumping water from the drain system, and
distribution manifold. This will short-circuit the
spraying it on the surface of the landfarm. How-
flow of nutrients and oxygen through the entire
ever, the pumping rate for the underdrain system
soil mass, potentially slowing the rate of
is limited by the rate of water percolation through
remediation. Third, it may be necessary to install
the filter rock to the perforated drainage pipe.
a heavier liner and to provide better protection
On the basis of testing and observation, land-
for it by installing cushion fabric or a layer of
farming of the petroleum-contaminated soils from
sand.
the old burn pit site appears to be a viable method
The more rapid remediation attained with the
of remediation. With appropriate nutrient amend-
recirculating leachbed can be used alone or in
ments, the landfarm may be used to remediate
conjunction with landfarming and could provide
1100 to 1600 yd3 (841 to 1223 m3) of material
an expedient means to treat highly contaminated
during one summer season.
soil. This would increase the potential for land-
farming of the remaining soil without liner
requirements.
Infiltration gallery
Because of the difficulty in obtaining suffi-
Because of the relatively small amount of
cient data from an in-situ, saturated system, it is
soil that the leachbed can remediate relative to
difficult to draw any definite conclusions regard-
the quantity of contaminated soil located at the
ing the operation of the infiltration gallery. How-
CFR site, there are no plans to reconstruct it.
ever, some general observations can be made.
Contaminated soils in the pit will be moved to
The significant reduction in the iron (Fe) con-
the landfarm in the future. The equipment used
centrations in the groundwater during operation
with the leach bed may be useful for remedi-
of the facility tells us that iron is precipitating.
ating fuel-contaminated water generated in
This was expected, but, to date, it has not exces-
conjunction with fire training exercises at the
sively plugged the gallery walls or bottom. There
new lined fire-training pit recently constructed
has been some mounding of water in the gallery,
at FIA.
indicating that the precipitation of iron is slow-
ing the movement of water away from the gallery.
LITERATURE CITED
Dissolved oxygen concentrations at the gal-
lery monitoring wells remained low (less than 10
Anonymous (1991) Contract documents and
mg/L) throughout the operating periods. Oxy-
specifications for Fairbanks International Airport,
gen concentrations were slightly higher in the
Experimental Bioremediation Project, Project
wells closer to the gallery, showing the influence
Number 65096. Sponsored by the Department of
of the aeration system. Also, phosphate (PO4)
Transportation and Public Facilities, Statewide
was not detected at any of the wells during the
Research, Fairbanks International Airport, USA
period when it was added to the infiltration
Cold Regions Research and Engineering Labora-
water at a final concentration of approximately 4
tory, and USA Construction Engineering Research
mg/L. These factors would be expected to lower
Laboratory.
the total population of microorganisms and slow
Braley, W .A. (1991) The Fairbanks International
their metabolic processes.
Airport experimental bioremediation project. Pre-
Plans are to continue monitoring of ground-
sented at the BP Exploration Alaska Soil Remediation
water concentrations of aromatic hydrocarbons
Workshop, 1920 November, Anchorage, Alaska.
in wells next to the infiltration gallery. Soil con-
Braley, W .A. (1993) The Fairbanks International
taminant levels around the gallery will be quan-
Airport experimental bioremediation project pre-
tified to see if more treatment is required. Further
liminary report. Alaska Department of Transpor-
17
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