Dames & Moore, 1999 - USDA Forest Service

for good quality riprap would necessitate a detailed assessment to determine the rock-type distribution
followed by compositional hi-grading, which may not be practical andlor feasible. Two additional source
areas, Holden Road at 3-mile and Holden Road at 4-mile, appear to contain rock-types with similar
composition to the rock quarry, are not significantly closer than the rock quarry and, therefore, would not
appear to be a good source. In addition, the sources would require further assessment to determine quantity,
compositional quality and techniques for quarry development.
The talus pile at 9-mile has a high potential for a good riprap source. Preliminary findings suggest higher
compositional grade of rock (e.g., relatively competent boulder hardness, sufficient quantity of large boulder
sizes). In addition, the source is near the Site. However, there are a variety of rock types found throughout
the talus pile, so some segregation may be required. In any case, the talus pile will need further assessment
of accessibility, as there may be rock fall or slope stability hazards during excavation.
The waste rock piles southwest of tailings pile 1 were also considered as possible riprap sources, due to
local accessibility. However, the range of sizes and quality is unknown (e.g., hardness tests were not
conducted), and based on visual observations, the maximum boulder size appears to be limited. In addition,
there may be a potential for mineralization which dould adversely affect water quality.
The area east of tailings pile 3 and the slopes south of the three tailings piles were assessed for potential
riprap sources. Neither area is apparently a good riprap source due to: (1) a predominance of fines that
would necessitate hi-grading and large quany sizes, and (2) the maximum boulder size is likely not large
enough to prevent removal by stream action during high flow conditions.
It should be noted that a review of available geologic maps for the portion of Railroad Creek outside the
Glacier Peak Wilderness indicates a number of dikes that include "alaskite" and "quartz diorite." Alaskite is
an igneous rock with a greater proportion of alkali feldspar minerals and is, therefore, considered the most
stable of the granitic rocks in the weathering environment. It is possible that some of the boulders present as
riprap along the base of the tailings piles, as well as in the potential riprap sources identified above, may
actually be alaskite. However, these rocks were combined with the other competent granites and
granodiorites noted herein because they were not abundant as an individual riprap type. It is also possible
that alaskite may be present in the form of dikes within the portions of the wilderness area near Lucerne,
Martin Ridge, and/or Tenmile Creek; however, the deposits within the wilderness area were not evaluated in
the field due to being considered inaccessible.
4.3 SURFACE WATER HYDROLOGY
4.3.1 Regional Climate and Hydrology
The climate in the Lake Chelan region is characterized by hot, dry summers and mild to severe winters.
Average monthly temperature varies from highs in the 30s (in degrees C) in July and August to extreme low
temperatures well below 0 in January. Average temperatures are generally below freezing between the
months of November and March. Temperatures vary with elevation and in most circumstances decrease
with elevation. Typically, temperatures decrease by about 2 degrees C for every one thousand feet of
elevation gain (Wallace and Hobbs, 1977); however, this lapse rate can vary seasonally and with particular
weather conditions.
G:\WPDATA\OOSWEPORTSWOLDEN-ZUUWdUUWdDOC
17693-005-019Uuly 19.1999:4:51 PM,DRAFT FINAL RI REPORT