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.
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 more silty 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 Physical Setup and Operation
Site setup included initial site delineation; obtaining time-zero samples; collecting, compositing,
preparing and installing soil socks for later sampling; data-logger setup; and seeding and nutrient
additions. Site installation was conducted during the summer of 1998. At the Barrow site,
seeding and fertilizing were not done until the summer of 1999 due to the brief summer there.
One of the concepts associated with using rhizosphere-enhanced treatment is freedom from
utilities and infrastructure. We had either electrical power or battery power at the sites, but this
was merely to operate temperature data loggers; electric power is not required for the operative
processes to proceed. During the demonstrations, a CRREL representative visited the sites
periodically during the growing season to change data storage cans and check on the status of the
sites. We were unable to keep the data loggers, batteries, and associated equipment secure at the
sites. For data analysis, we used air temperature data obtained from the National Oceanographic
and Atmospheric Administration (NOAA) to calculate growing degree-days at the sites.
13