ESTCP Project #1011, Rhizosphere
Final Report
north edge of the North Salt Lagoon. The tanks and pipes were removed in 1990. Two of the
tanks are known to have leaked. Investigations in 1990 and 1991 found gasoline and diesel in 5
to 20% of the samples with levels up to 2840 mg/kg. Benzene, toluene, ethylbenzene, xylenes,
halogenated aliphatic hydrocarbons, solvents, phenolic, polycyclic aromatic hydrocarbons, and
inorganic chemicals were also found in soil and active-zone water. TPH concentrations ranged
from 47 to 9400 mg/kg and averaged 1278 mg/kg. Lead was also detected in all soil samples,
ranging from 8.1 to 365 mg/kg. In 1994, no GRO was detected in six shallow soil samples, but
concentrations of 838 mg/kg were found 3 ft below ground. DRO and total residual petroleum
(TRP) ranged from 200 to 260 mg/kg and 230 to 250 mg/kg. Our partner was the Navy, and we
worked with Battelle.
The Barrow climate is very cold and dry; temperatures range from 19 F in February to 40 F in
July. The average annual precipitation is 14.6 inches. High relative humidity (90 to 95%) in the
summer leads to foggy conditions about 25% of the time. Ground-based inversions are common
in the winter and can concentrate airborne pollutants in low-lying areas when not dissipated by
wind. Barrow's location between the Aleutian low-pressure system and the polar high-pressure
system creates continual surface winds, predominately easterly and generally strongest in the fall
and early winter.
Barrow is on the northwest edge of an extensive coastal plain. Soils are dominated by marine
beach deposits consisting of coarse sand and gravel. Some finer deposits of silt, clay, and peat
occur in drained lake basins and in places along beach ridges where wave action has not caused
reworking. Soils are likely to be siltier in vegetated locations. In the Barrow area, a blue-black
clay has been reported at depths of 10 to 60 ft.
Seasonal freeze-thaw and permafrost processes dominate the site surface hydrology and
hydrogeology. The combination of permafrost and low-elevation terrain leads to the formation of
thaw lakes and polygons (cracked, patterned ground characteristic of the Arctic far north). A few
small streams form from surface runoff immediately after ice breakup, typically mid-to-late July.
Soils at the surface are frozen through most of the year, reaching a maximum thawed depth of 22
to 55 in. by August or September. This "active zone" usually refreezes by late October, but
heated buildings or the removal of the upper layers of soil disturbs it. Also, fine vegetated soils
will thaw more slowly and to lesser depths than coarse, non-vegetated soils. Groundwater is
confined to the active zone above the impermeable permafrost, and active-zone water movement
is considered to be insignificant at NARL.
3.4 Pre-Demonstration Testing and Analysis
To initially characterize the general contaminant distribution at the site and to find the best
location for the demonstration plots, we analyzed an initial set of samples in a grid pattern by
organic vapor analysis. This helped us locate our demonstration plots. Additionally, an initial set
of samples was taken at each site to provide t0 data.
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