Dames & Moore, 1999 - USDA Forest Service

indicated that the groundwater at these locations is apparently impacted by past mining-related activities.
(HBKG-I is situated within an area immediately west of tailings pile 1 with impacted groundwater, and
HBKG-2 was installed immediately west of an abandoned access road constructed of rock that may have
contained limited mineralization.) The ability to install additional upgradient wells was limited due to the
presence of the Glacier Peak Wilderness boundary and difficult access conditions for conventional
drilling equipment. Consequently, background groundwater quality sampling was accomplished on the
north side of Railroad Creek at well HV-3 (also shown as H-3), which is located topographically above
most of Holden Village and appears to be representative of background conditions.
The USBM also installed a groundwater monitoring well (CCBKG) near Copper Creek at the southwest
comer of tailings pile 2. This well was dry during the RI groundwater monitoring efforts and was not
sampled.
Since seeps are considered relatively representative of shallow groundwater, an attempt was made to
locate and sample seeps apparently upgradient of the Site. SP-26 was located, near the western limit of
apparent historical mining-related activity on the Site, and sampled. In May 1998, a sample was collected
at seep SP-27 (~igure 3.2-1) located farther up-valley. This seep is suspected to be meteoric in nature and
not reflective of groundwater. No other seeps were observed upgradient of the Site.
Lab analyte lists for these locations are similar to the Site analyte lists for groundwater and seeps,
respectively. The results of the laboratory analyses are presented in Section 5.4.2.2.
3.3.1.5 Lucerne Water-Supply Well
Referring to Figure 3.3-1 and Tables 3.0-1,3.2-2 and 3.2-4, water quality samples were collected from the
well associated with the potable water supply for the USFS guard station facility in Lucerne during both
the May and September 1997 sampling rounds. In both instances sufficient water was pumped to purge
the supply system and allow water quality parameters to stabilize. Samples were analyzed for the same
primary analyte list as site groundwater samples (aluminum, barium, beryllium, cadmium, calcium,
chromium, copper, iron, lead, magnesium, manganese, nickel, potassium, silver, sodium, zinc, total
dissolved solids, total suspended solids, sulfate, alkalinity, hardness, and field parameters). The results of
the laboratory analyses are presented in Section 5.4.2.8.
3.3.1.6 Electromagnetic and Self Potential Geophysical Surveys
A subcontractor (Northwest Geophysical Associates, Inc.) to Dames & Moore completed an
electromagnetic (EM) survey of select areas across the Site in order to better characterize potential
pathways of near-surface, metals-containing water through the near surface soil. The SAP outlined a
program to utilize either EM or self-potential geophysical methods. EM survey methods were used based
on field conditions encountered and the relative success utilizing this method.
Referring to Figure 3.1-2 and Table 3.0-1 (under "Geophysical Survey Lines"), the EM survey was
completed in two primary areas: the western portion of the Site, or mine support area, and the area
immediately east of tailings pile 3, in an area where seeps were observed. The survey of the western
portion of the Site consisted of two se ic lines (EM-I and EM-2). The lines were located across an
affected area based on field pH and conducti % ity readings collected from seeps. The first line (EM-I) was
completed adjacent to Railroad Creek between the upstream most seep which appeared to contain
G:\wpdataVKMkpomUIolden-2\riU-0.doc 3-14 DAMES & MOORE
17693-005-019Uuly 19.1999;2:07 PMlDRAFT FINAL RI REPORT