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Dames & Moore, 1999 - USDA Forest Service

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groundwater was encountered at approximately 4 ft bgs at locations DMLG-4 and DMLG-5 and at 7 !4 fi<br />

bgs at DMLG-2. Concentrations of copper and lead were above background but below MTCA levels in<br />

samples collected from test pits DMLG-1 and DMLG-3' located at the southern and northern ends of the<br />

lagoon area. Cadmium was detected but was below background at locations DMLG- 1 and DMLG-3.<br />

PCOCs identified in the surface lagoon soil include beryllium, aluminum, and iron. PCOCs identified in<br />

the subsurface soil include cadmium, copper, and lead at depths of 2 to 7 !h ft bgs within and adjacent to<br />

the perimeter of locations DMLG-2, DMLG-4, and DMLG-5. Iron and aluminum were identified as<br />

PCOCs in subsurface soil based on the single sample result from 1997 (Lagoon 2'); however, the vertical<br />

and lateral extent of these metals in the lagoon was not assessed. Additional PCOCs were not identified'<br />

at testpits DMLG- 1 and DMLG-3 located on the southern and northern ends of the lagoon.<br />

5.2.5.2 Organic Results<br />

PCBs were not detected in the surface or subsurface lagoon samples. Total petroleum hydrocarbons<br />

(diesel and heavier) were detected in surface and subsurface samples. Concentrations ranged from 230 to<br />

2,200 mgtkg, which is above the MTCA Method A level (200 mgkg). TPH (diesel and heavier than<br />

diesel) are retained as PCOCs in subsurface soils in the lagoon. Soil to a depth of 4ft bgs in the area<br />

bounded by test pits DMLG-2, DMLG-4, and DMLG-5 and to a depth of 2ft bgs in the area surrounding<br />

test pits DMLG- 1 and DMLG-3 of the lagoon is affected.<br />

5.2.6 Tailings Piles<br />

5.2.6.1 Historical Tailings Samples<br />

Historical surface tailings samples were collected by USBM (1995) and USGS (1994 and 1995). The<br />

following historical surface sample locations are associated with each tailings pile:<br />

-<br />

Tailings Pile 1<br />

HT I -2A<br />

HT I -2B<br />

503T<br />

504T<br />

505TA<br />

505TB<br />

The sample locations are provided in Figure 5.2-3.<br />

Tailings Pile 2<br />

HT2-2A<br />

HT2-2B<br />

TP2-4 (subsurface) .<br />

502T<br />

The samples were analyzed for a similar suite of metals, with some exceptions. The USGS samples were<br />

not analyzed for mercury, nickel, selenium, or thallium. Tailings samples collected by the USBM were not<br />

analyzed for molybdenum and uranium. The data are summarized in Table 5.2-4.<br />

Aluminum, barium, copper, iron, lead, molybdenum, silver, thallium, and zinc concentrations were above<br />

area background in the majority of surface tailings. Mercury was detected in several samples above the<br />

Yakima Basin background value (Ecology). The Yakima Basin published background value for mercury<br />

was used for data evaluation as mercury was not included in the area background assessment. Metal<br />

\U)M-SEAI\VOLI\COMMOMWP\WDATA\OOS\REPORTSWOLDEN-XRlU-O-Odo5 5- 1 0<br />

17693605619Wuly 28. <strong>1999</strong>;11:09 AM;DW FINAL RI REPORT<br />

Tailings Pile 3<br />

HT3-2A<br />

HT3-2B<br />

4 chc 360<br />

SOOT<br />

501T

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