Dames & Moore, 1999 - USDA Forest Service

PCOCs in soil at the maintenance yard include copper. lead, cadmium, and iron in surface soil. Arsenic is a
PCOC in surface soil only at the "Storage" location. Aluminum is considered a PCOC in subsurface soil at
DMSS- 10.
5.2.4.2 Organic Results
The surface and subsurface samples collected in the maintenance yard were analyzed for PCBs and total
petroleum hydrocarbons (as gasoline,.diesel, and heavier than diesel). PCBs were detected in surface soil
collected at DMSS-9, DMSS-10, and "Storage" and ranged from 17 to 46 pgikg. These levels are well
below the MTCA Method A level (1 000 pgkg). PCBs were not detected in subsurface soils.
TPH concentrations (diesel and heavier than diesel) were above the MTCA ~ethbd A level (200 m@g) at
all sample locations with the exception of subsurface sample DMSS-9 collected at 2 feet bgs. TPH
concentrations in the gasoline range were above the MTCA Method A cleanup level at DMSS-I0 and
DMSS-10 2' (surface and subsurface).
TPH as diesel, heavier than diesel, and gasoline are considered PCOCs in the maintenance yard.
5.2.5 Lagoon Area
A surface soil sample (Lagoon 6,") and a subsurface sample (Lagoon 27, were collected in 1997 from the
surface and 2 ft bgs, respectively. The samples were analyzed for metals and organic compounds (TPH
and PCBs). Based on the analytical data collected in 1997 and summarized in Table 5.2- 1, additional test
pits (DMLG-I, DMLG-2, DMLG-3, DMLG-4, and DMLG-5) were completed in the lagoon in 1998 to
assess the vertical and lateral extent of specific chemical constituents. Samples collected in 1998 were
analyzed for cadmium, copper, lead, and total petroleum hydrocarbons (TPH diesel and heavier) based on
the PCOCs preliminarily identified from the 1997 Rl data. The sample and test pit locations are shown
on Figures 5.2-1 and 5.2-4 and the analytical data are summarized in Table 5.2-1.
5.2.5.1 Inorganic Results
Aluminum, barium, beryllium, copper, iron, lead, molybdenum, silver, uranium, and zinc were above
background in the surface sample Lagoon 6". Concentrations were below MTCA levels with the
exception of beryllium (0.3 mgkg) which was slightly above the MTCA Method B level (0.23 mag).
Aluminum (33,500 m ag) and iron (36,200 m@g) were above background (20,900 m ag and 36,200
mgkg, respectively).
Aluminum, cadmium, copper, iron, lead, molybdenum, silver, thallium, uranium, and zinc were above
background in the subsurface samples collected from the lagoon. Concentrations were below MTCA
levels with the exception of cadmium, copper, and lead. Aluminum (3 1,300 mgkg) and iron (1 01,000
mgkg) were above background (20,900 m ag and 24,100 mgkg, respectively). The vertical and lateral
extent of cadmium, copper, and lead was evaluated based on the test pit samples collected in 1998.
The data show that concentrations of cadmium, copper, and/or lead are above MTCA levels in the soil
from 2 to 4 feet bgs at test pit locations DMLG-2, DMLG-4, and DMLG-5. The highest concentrations of
metals detected in the lagoon samples are found in samples from these three test pits. At 7 '/z ft bgs in test
pit DMLG-2, cadmium and copper are above MTCA levels. Test pits were not extended deeper as
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17693-005-0 19Uuly 28. 1999; 1 1 :09 AM;DRAFT FINAL RI REPORT