Dames & Moore, 1999 - USDA Forest Service

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8.1 INTRODUCTION
8.0 DISCUSSION AND INTERPRETATION OF FINDINGS
The geology, surface and subsurface soils, surface water, groundwater, seeps, sediments, air. and ecological
conditions of the Holden Mine area and portions of the Railroad Creek watershed, were evaluated during the
RI utilizing data collected by Dames & Moore and others. The R1 also included evaluation of the presence
or absence of asbestos-containing materials in the abandoned mill building, the presence or absence of
underground storage tanks and associated possible petroleum hydrocarbons in the Winston Home Sites area.
an evaluation of geologic hazards on the Site, an assessment of potential rock and soil sources, and human
health and ecological risk assessments. In addition, the RI characterized surface water and ecological
conditions in three reference reach locations north of the Railroad Creek watershed in the Stehekin River
Watershed (Bridge Creek, Company Creek, and South Fork of Agnes Creek) (Figures 8.1-1 through 8.1-5).
This section presents a summary of the key findings and interpretations of the Site surface and subsurface
conditions in terms of the geology; hydrology; hydrogeology; aquatic and terrestrial biota; the nature and
extent of contamination in surface and subsurface soils, groundwater, surface water, and sediment;
characterization of the transport and fate of contaminants; and the potential for human health and ecological
risks associated with the Site. The interpretations of the settings for the aquatic reference reaches outside the
Railroad Creek watershed are presented in this secti,on in order to evaluate the comparability of data
collected from these areas with the Railroad Creek data.
Due to the complexity of the Site conditions, and to assist in communicating the findings, some redundancy
exists between the previous report text and this section of the report; the relevant previous sections of the
report are referenced as appropriate.
I 8.2 INTERPRETATION OF THE SITE SETTING
The Site is located within the Railroad Creek watershed. The Railroad Creek watershed includes the entire
watershed area from Lyman Lake to Lake Chelan; and the aquatic reference reaches indlude one stream
segment each in Bridge Creek, South Fork of Agnes Creek, and Company Creek which were sampled for
aquatic biota and water quality for comparison to appropriate segments of Railroad Creek. The Site
includes the general area within the Railroad Creek valley between the upstream wilderness boundary at
surface water sampling station RC-6, to immediately downstream of the eastern end of the tailings piles at
seep sampling station SP-2 1.
Referring to Section 4.0 for a complete discussion of findings, the following section summarizes the most
important elements of the setting in terms of the Site and aquatic reference reach areas.
8.2.1 Physiography
8.2.1.1 Site
The Holden Mine is situated in a remote area on the eastern slopes the Cascade Mountains and surrounded
on three sides by established wilderness and one side by National Forest System land managed forest land
17693-005-019Vuly 28.1999:10:24 AM;DRAFT FINAL RI REPORT