Dames & Moore, 1999 - USDA Forest Service

where Railroad Creek flows directly atop bedrock), RC-9 (an aquatics sampling station established upstream
of the Copper Creek confluence adjacent to tailings pile l), RC-10 (approximately three miles downstream
of tailings pile 3), and RC-11 (established imxiediate~'~ upstream of the Holden Creek confluence aAer it
was discovered that Howe Sound Company likely conducted limited mineral exploration in the Holden
Creek watershed).
Streamflow monitoring stations on Copper Creek include CC-1 upstream of the tailings piles (established by
PNL and the USFS), CC-2 near the confluence of Copper Creek and Railroad Creek (also established by
PNL and the USFS), and CC-DICC-Dl, which is the Copper Creek diversion (established at the request of
the Agencies). CC-DICC-Dl flow is diverted from Copper Creek upstream of CC-I and routed through the
hydroelectric plant. Flow from CC-DICC-Dl is also diverted for water use at Holden Village. Flow was
also monitored in the portal drainage at stations P- 1 (where the drainage flows from the mine portal) and P-5
(upstream of the confluence with Railroad Creek).
Staff gages for measuring water levels are located at stations RC-2, RC-4 and RC-6 in Railroad Creek.
Additionally, a continuously recording water level recorder (Troll) was installed in the stilling well at,RC-
4 on May 24, 1997. The Troll was removed during the winter due to the low water levels and freezing
temperatures. A staff gage is also located behind the weir that controls flow out of the hydroelectric plant
in the Copper Creek diversion.
Upstream of Site
Less than one mile upstream of the Site, Big Creek enters Railroad Creek from the south and nearly doubles
the flow when compared to Railroad Creek above the confluence. Slightly upstream of the Big Creek and
Railroad Creek confluence, Holden Creek enters Railroad Creek from the north. Holden Creek drains the
Holden Lake basin to the north and provides less than 10 percent of the total flow of Railroad Creek as
measured at the nearest downstream station (RC-6).
Adjacent to Site
Due to the difficulty in physically obtaining accurate flow measurements in the field during high flow
conditions in the May to June time period, it is not possible to determine whether Railroad Creek is
consistently in a gaining condition (water flows into the creek and gains total volume as it flows down
valley) or possibly in a losing condition (water is lost to the surrounding soil as the stream flows
downstream) for segments of the stream adjacent to the Site.
The portion of Railroad Creek between the portal drainage confluence at P-5 and RC-4 may gain or lose
minor amounts of flow during portions of the year. Further downstream, Railroad Creek adjacent to the
tailings piles is apparently in a gaining condition' during the spring runoff period. However, the portion of
the creek adjacent to tailings pile 3 is in a losing condition at least during the fall and probably through the
winter months.
Iron-oxide staining and interstitial flocculent were observed on the stream bed for the portion of Railroad
Creek from tailings pile 1 to the east end of tailings pile 3. The aquatic sampling location RC-9, upstream of
the Copper Creek confluence, was noted to be the transition zone. The creek substrate for the upstream
portion of the sampling station did not contain significant staining andlor flocculent. In contrast, the
downstream portion of the creek substrate to the east end of tailings pile 3 was predominantly stained and
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17693-005-019Uuly 28. 1999;10:24 AM:DRAFT FINAL RI REPORT