Dames & Moore, 1999 - USDA Forest Service

Groundwater discharge from the tailings piles into Railroad Creek occurs in the form of springs or seeps
and diffuse groundwater flow into the creek substrate.
• The tailings piles are the primary source of dissolved and total iron loading to Railroad
Creek throughout the year.
• The precipitation of iron results in the cementing of portions of the Railroad Creek
streambank, principally at three of the more prominent seep discharges near the northeast
corner of tailings pile 1, and the northwest comer of tailings pile 2.
Sediment Quality
Most of the dissolved iron from the tailings piles is converted to a fine precipitate or .
flocculent after it enters the stream.
The sediment in Railroad Creek consists mostly of gravel, cobbles, and boulders. The stream gradient is
relatively moderate near the Site and steeper upstream and downstream of the Site; however, the gradient
appears to be too steep to allow deposition of sediment. The concentrations of metals in Railroad Creek
sediments do not indicated the potential for adverse effects based on Ecology guidance values. Sediment
samples were collected frdm both the Lucerne Bar (near the mouth of Railroad Creek in Lake Chelan)
and a reference site near the mouth of the Stehekin River. The results indicated concentrations of zinc
slightly above FSQVs for only one sample out of 12.collected and analyzed. The remainder of the results
were below the FSQVs. These results suggest a low potential for adverse effects in sediment at Lucerne
Bar.
Ecological Conditions .
The aquatic survey consisted of the sampling of aquatic insects (benthic macroinvertebrates) and fish at
eight locations in Railroad Creek (six station adjacent and downstream of the Site, and two upstream
reference or control stations) and three locations in reference streams in the Stehekin River watershed
which is outside the Railroad Creek watershed. The sampling was completed during the month of
September (safety considerations precluded high flow sampling during the spring melt period). The fish
survey included the use of both snorkeling and electrofishing methods. The results of the sampling
indicated:
The populations of benthic macroinvertebrates and fish found adjacent to the upstream and
westernmost tailings piles, but outside the area of iron-oxide flocculent, were similar to
those found upstream of the Site.. This area is adjacent to the tailings pile but downstream
of the portal drainage and the major sources of dissolved cadmium, copper, and zinc
loading into Railroad Creek.
• The comparability of fish data collected from two of the three control stations for the mid to
lower portions of Railroad Creek is questionable due to stream habitat dissimilarities. The
control site for the mid-Railroad Creek segment (Bridge Creek) included a relatively deep
pool in which most fish were caught. The control site for the mouth of Railroad Creek
(Company Creek) was dissimilar in size and was located immediately adjacent to a salmon
spawning ground.
G:\WDATA\OOSWEPORTS\HOLDEN-ZWECLlfIVE SUMMARY.doc
17693-005-019Uuly 28. 1999;12:16 PM;DRAFT FINAL RI REPORT ES-9 DAMES & MOORE