Dames & Moore, 1999 - USDA Forest Service

aquifer from the portal drainage, observed as seep flow into the lagoon, provides adequate recharge to
provide sufficient discharge from the alluvial aquifer to account for flow in Railroad Creek.
Reach 2 - RC-4 to RC-2 (Table 4.4-10, and Figures 4.4-20 and 4.4-21)
Similar to Reach 1, the sum of the water balance estimates generally indicate an error bias toward
negative values, although the estimate errors in this reach may also be slightly positive. The water
balance equation for Reach 2 is expressed as:
where:
where:
Qrc2 = 5 1 5 to 529 cfs (spring)
Qrc4 = 460 cfs (spring)
Qa = 5.3 cfs (spring)
Qsr = 3.4 cfs (spring)
Qt = 59.8 cfs (spring)
Qrc2 = Qrc4 + Qa + Qsr + Qt (Reference Equation 4- 14)
140 to 144 cfs (fall)
125 cfs (fall)
1.6 cfs (fall)
0 cfs (fall)
16.3 cfs (fall)
Qr = Qrc2 - (Qrc4 + Qa + Qsr + Qt) (4- 16)
Qr = - 13.5 to 0.5 cfs (spring) -2.9 to 1.1 cfs (fall)
Relative to RC-4, the estimate errors range from approximately 1 percent to -3 percent. This magnitude
of error is well within the measurement error for flow in Railroad Creek. Thus, there does not appear to
be any missing flow components that are large enough to impact the water balance.
There is a gain in flow in Railroad Creek between RC-4 (Qrc4) and RC-2 (Qrc2) for both the MaylJune
and September 1997 time periods; the increased flow was measured to range between 12 and 15 percent.
During the MaylJune 1997 time period, there was an estimated gain of direct surface water runoff
contribution to Railroad Creek from the north bank of Railroad Creek (Qsr north bank) of less than 0.7
percent. There was no gain of surface water from the south bank of Railroad Creek (Qsr south bank) due
to the presence of surface water interceptor ditches to the south of the tailings piles. During the
September time period, the runoff from the south and north banks was assumed to be approaching zero.
There was no measurable contribution of water flow from the bedrock aquifer for both the MayiJune and
September time periods within this reach.
4.5 CULTURAL RESOURCES
The 1975 ORB report noted that the Site is eligible for nomination as a historic site. This was confirmed by
a USFS, Pacific Northwest Region, Determination of Significance and Effect form which indicated that the
Site was determined to be eligible as early as 1979. A "Draft Determination of Eligibility Report," dated
1991, was prepared by the USFS and nominated the Holden Mine Historic District to the National Register