Dames & Moore, 1999 - USDA Forest Service

i
flow associated with two seeps adjacent to Railroad Creek, seeps SP-12 and SP-23. In addition, it is possible
that some of the Honeymoon Heights intermittent drainage water migrates into the underground mine
through fractures and joints in the bedrock. A dye test was completed during the RI to test the hypothesis
that discharge from the SP-12 and SP-23 seeps and 1500-level main portal drainage are connected with the
Honeymoon Heights intermittent drainage; however, the results were inconclusive.
Eastern Portion of Site
Snow accumulates atop the tailings piles during the winter months and melts during the spring runoff
period. A series of the trenches were constructed between 1989 and 199 1 up slope and on the surface of the
tailings piles with the intent of intercepting surface water run on. and reducing the ponding of water on top
of the piles. Most of the water is conveyed in the ditches in the surface of the tailings piles which eventually
discharges either to Copper Creek or Railroad Creek. The ditch systems serve to divert water off the tailings
piles but do not prevent ponding of water in contact with tailings.
A series of three ditches were constructed on the surface of tailings pile 1. The ditches drain water to the
north to Copper Creek Diversion and to the east to Copper Creek. The ditch located in the western portion
of the tailings pile also transmits seep water which emanates from the base of the east waste rock pile. One
of the ditches present along the southern margin of the tailings pile was observed to be draining into what
appears to be an abandoned wood-lined decant tower which was not plugged during the 1989 to 1991
tailings pile rehabilitation. , .
Tailings piles 2 and 3 also have a system of drainage ditches on the surface of the piles. The ditches divert
surface water run on to the east indirectly into Railroad Creek at seep SP-2 1, east of tailings pile 3. A series
of ditches were also observed in a road cut above tailings pile 3; the ditch appears to intercept some of the
surface water run on before it comes into contact with the tailings piles. The water,that drains to the east
From tailings piles 2 and 3 enters a wetland area to the east of tailings pile 3 before eventually discharging to
Railroad Creek.
8.2.3.6 Lake Chelan
Lake Chelan is the largest and deepest natural lake in Washington State. The lake is more 50 miles long
with an average width of one mile. It is the third deepest lake in the continental United States. The deepest
portion of the lake is in the Lucerne Basin, approximately mid-way up the lake and is approximately 453
meters (1,486 feet) deep.
Railroad Creek is the second largest hydrologic source to Lake Chelan, historically contributing
approximately 10 percent of the annual input to the basin. The largest is the Stehekin River, at the northern
end of the lake. The mouth of the Railroad Creek is situated on the west side of the lake, approximately 15
miles south of the northern end of the lake. Sediments transported by Railroad Creek are deposited in a
delta near the mouth of the creek. However, the Stehekin River contributes more sediment to Lake Chelan
than does Railroad Creek.
A dam is present at the southernmost end of the lake; the dam raises the water as much as 21 feet above the
pre-dam level. During summer, the lake level is approximately 1,100 feet above sea level. When full, the
lake has an area of about 52 square miles. The water flows through the dam, over a water falls to the
Columbia River. There is no direct pathway for fish to migrate from the Columbia River to Lake Chelan.
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17693-005-019Uuly 28,1999:10:24 AM:DRAFT FMAL RI REPORT