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Dames & Moore, 1999 - USDA Forest Service

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concentrations were not above MTCA levels. Iron ranged from 54,000 mgkg to 85,300 mg/kg, above<br />

background (24,100 mgkg). Aluminum ranged from 32,000 mgkg to 44,000 mgkg.<br />

A subsurface tailings sample, TP2-4 (5 to 10 fi bgs), was collected by the USBM in 1994. Barium,<br />

cadmium, copper, iron, lead, mercury, thallium, and zinc concentrations were above background;<br />

however MTCA levels were not exceeded with the exception of cadmium. Cadmium (16.2 mg/kg) was<br />

above the MTCA Method A level (2 mgkg). Iron (61,400 mgkg) was above background (24,100<br />

mgkg).<br />

Aluminum concentrations were significantly greater in the samples collected by the USGS than those<br />

collected by the USBM. It was determined that the USGS samples were collected from the surface tailings<br />

at the toes of the tailings piles whereas the USBM and RI samples were collected on the top of the tailings<br />

piles. Additional metals detected at the toe of the slopes were above concentrations detected on the tops of<br />

the tailings piles. However, both of the data sets were considered when reviewing the data for PCOCs and<br />

comparing to the RI data.<br />

5.2.6.2 RI Tailings Samples<br />

Surface and subsurface samples were collected during the RI from each tailings pile. The samples<br />

associated with each tailings pile is provided below.<br />

Surface<br />

Subsurface<br />

Tailings Pile 1<br />

DMSS-I 1<br />

DMSS-I2<br />

DMSS-13<br />

DMTP 1-2<br />

DMTPI-3A<br />

DMTPI -3B<br />

DMTPI-4<br />

Tailings Pile 3<br />

DMSS-17<br />

DMSS-I8 ,<br />

DMSS- 19<br />

DMTP3- I<br />

DMTP3-2<br />

DMTP3-3A<br />

DMTP3-3B<br />

DMTP3-4A (7 feet bgs)<br />

DMTP3-4AX (Duplicate)<br />

DMTP3-4B (10 feet bgs)<br />

Sample locations are provided on Figure 5.2-1 and analytical data are summarized in Table 5.2-5.<br />

Samples were analyzed for metals only.<br />

Copper, iron, lead, molybdenum, and silver were above background in the surface samples collected;<br />

however, all concentrations were below available MTCA levels. Barium and zinc were above background<br />

in a limited number of samples, but well below MTCA levels. Iron ranged from 53,400 mgkg to 73,700<br />

mgkg. The USBM data from surface samples collected from the tops of the tailings piles was compared<br />

to RI data. The data were similar in concentration and were well within an order of magnitude.<br />

The subsurface samples were collected between 2.5 and 5 feet bgs from test pits completed in tailings<br />

piles 1, 2, and 3, with the exception of sample DMTP3-4A that was collected at 7 feet bgs and sample<br />

DMTP3-4B that was collected at 10 feet bgs in tailings pile 3.<br />

Aluminum, barium, cadmium, chromium, copper, iron, lead, molybdenum, nickel, silver, thallium,<br />

uranium, and zinc were above background in one or more subsurface samples collected. Concentrations<br />

\U)M~SEA~\V~L~\C~MM~N\WP\WPDATA\~~~PORTSW~LDEN-~UUU-~.~OE<br />

5- 1 1<br />

17693-0OS-019Vuly 28.<strong>1999</strong>;11:09 AM;DRAFT FINAL RI REPORT<br />

Tailings Pile 2<br />

DMSS- 14<br />

DMSS-I5<br />

DMSS-16<br />

DMTP2-IA<br />

DMTP2- I B<br />

DMTP2-2

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