Dames & Moore, 1999 - USDA Forest Service

were below MTCA levels with the following exceptions: cadmium (21 mgkg) and copper (12,400
mgkg) in sample DMTPI-3B and cadmium (147 mgkg) and copper (16,500 mg/kg) in sample DMTP2-
1A. Iron ranged from 26,800 mgkg to 87,500 mgkg. Aluminum (29,700 m&g) was above background
(20,900 mgkg) at one location (DMTP2- I A).
The subsurface historical data (TP2-4 collected 5 to 10 ft bgs) was compared to the data collected at
location DMTP2-2 (4 to 5 feet bgs) during the RI. Generally, the data were within an order of magnitude;
however, concentrations of cadmium, lead, and zinc reported in the USBM sample were 20 to 40 times
greater than the concentrations detected in the RI samples. Only cadmium levels in the USBM samples
were above MTCA levels.
Aluminum and iron are considered PCOCs in surface and subsurface tailings as it is above background; a
MTCA level is not currently established. Cadmium and copper are considered PCOCs in subsurface
tailings only.
5.2.7 Wind-Blown Tailings
Five surface soil samples (DMSS-20 through DMSS-24) that contained visual evidence of tailings were
collected downwind of RC-2 during the RI and were analyzed for metals only. Sample locations are shown
in Figure 5.2-5 and the data are summarized in Table 5.2-5.
Barium, copper, iron, lead, molybdenum, silver, and zinc were above background levels in one or more
samples collected. However, none of the concentrations were above available MTCA levels. Iron
concentrations ranged from 24,100 mgkg to 66,200 mgkg.
Iron is identified as a PCOC as it is above background and a MTCA level is not currently established.
5.2.8 Summary
Site-specific background values for metal concentrations were statistically calculated from surface soil
samples collected Specifically for area background assessment. Metals data collected from Holden
Village, the baseball field, maintenance yard, lagoon, tailings piles, and windblown tailings were
compared initially to background values. If concentrations 'were above background, the data were then
compared to available MTCA A or MTCA B cleanup levels. Metal concentrations above background and
MTCA cleanup levels were preliminarily selected as PCOCs and are summarized by location in Table
5.2-6. Exceptions to the PCOC assessment were cations (calcium, magnesium, potassium, and sodium),
aluminum and iron. The cations are generally considered nutrient metals and MTCA does not provide ,
cleanup levels for these metals. Aluminum and iron were considered PCOCs if the results were above
background as MTCA does not provide guidance for these metals.
Organic analytical data from the surface and subsurface soil samples collected from the lagoon and
maintenance yard were compared to MTCA Method A and Method B cleanup levels. Total petroleum
hydrocarbon concentrations above MTCA cleanup levels were considered PCOCs in subsurface soil in
the maintenance yard in a localized area and in surface/subsurface lagoon soils. Organic PCOCs are also
summarized in Table 5.2-6.
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17693405-0 19Uuly 28, 1999; 1 1 :2 1 AM:DRAFT FINAL RI REPORT