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Dames & Moore, 1999 - USDA Forest Service

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Groundwater discharge from the tailings piles into Railroad Creek occurs in the form of springs or seeps and<br />

diffuse groundwater flow into the creek substrate.<br />

a The tailings piles are the primary source of dissolved and total iron loading to Railroad Creek<br />

throughout the year.<br />

• The precipitation of iron results in the cementing of portions of the Railroad Creek<br />

areambank, principally at three of the more prominent seep discharges near the northeast<br />

comer of tailings pile 1, and the northwest comer of tailings pile 2.<br />

9.2.5 Sediment Quality<br />

Most of the dissolved iron from the tailings piles is converted to a fine precipitate or flocculent<br />

after it enters the stream.<br />

The sediment in Railroad Creek consists mostly of cobbles, and boulders. The stream gradient is<br />

relatively moderate near the Site and steeper upstream and downstream of the Site; however, the gradient<br />

appears to be too steep to allow deposition of sediment. The concentrations of metals in Railroad Creek<br />

sediments do not indicated the potential for adverse effects based on Ecology guidance values. Sediment<br />

samples were collected from both the Lucerne Bar (near the mouth of Railroad Creek in Lake Chelan) and a<br />

reference site near the mouth of the ~tehekin River. The results indicated concentrations of zinc slightly<br />

above FSQVs for only one sample out of 12 collected and analyzed. The remainder of the results were below<br />

the FSQVs. These results suggest a low potential for adverse effects in sediment at Lucerne Bar.<br />

9.2.6 Ecological Conditions<br />

The aquatic survey consisted of the sampling of aquatic insects (benthic macroinvertebrates) and fish at eight<br />

locations in Railroad Creek (six station adjacent and downstream of the 'Site, and two upstream reference or<br />

control stations) and three locations in reference streams in the Stehekin River watershed which is outside the<br />

Railroad Creek watershed. The sampling was completed during the month of September (safety<br />

considerations precluded high flow sampling during the spring melt period). The fish survey included the<br />

use of both snorkeling and electrofishing methods. The results of the sampling indicated:<br />

• The populations of benthic macroinvertebrates and fish found adjacent to the upstream and<br />

westernmost tailings piles, but outside the area of iron-oxide flocculent, were similar to those<br />

found upstream of the Site. This area is adjacent to the tailings pile but downstream of the<br />

portal drainage and the major sources of dissolved cadmium, copper, and zinc loading into<br />

Railroad Creek.<br />

a The comparability of fish data collected from two of the three control stations for the mid to<br />

lower portions of Railroad Creek is questionable due to swam habitat dissimilarities. The<br />

control site for the mid-Railroad Creek segment (Bridge Creek) included a relatively deep pool<br />

in which most fish were caught. The control site for the mouth of Railroad Creek (Company<br />

Creek) was dissimilar in size and was located immediately adjacent to a salmon spawning<br />

ground.<br />

• Benthic macroinvertebrates and fish populations were reduced in Railroad Creek within the<br />

segment of the stream with iron-oxide staining and flocculent on the substrate. This extended<br />

from the northeast comer of tailings pile 1 to station RC-5, located approximately one-half<br />

mile downstream of tailings pile 3.<br />

O.\WPDATAU)O~EPORTS\HOLDEN-~UU\~-~.~OC 9-6<br />

17693-005-019Vuly 28, <strong>1999</strong>;10:07 AM;DRAF? FINAL RI REPORT

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