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<br />Golds- Associates Ine.
<br />200 Color. Boulevard. Suite 500
<br />tnkewood. CO USA 80228
<br />Telenhonei303)9B0-OSdO
<br />Fcx(3C3)9B5-2080
<br />August 18, 1995
<br />Cripple Creek ~ Victor Gold Mining Company
<br />2755 State Highway 67
<br />Victor, CO 80860
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<br />Our Ref.: 953-2900.007
<br />RE: STLIBBED T PRIMARY UNDERDRAL~' ENFLANCE.'1~NT
<br />Dear John:
<br />Golder Associates Inc. (Golder) would like to take this opportunity to discuss the
<br />enhancements that have been incorporated to the "stubbed T" Primary Underdrain detail
<br />for the Phase II Heap Leach Pad (Pad).
<br />The stubbed T Primary tnderdrain constructed beneath the Phase I Pad during 1994
<br />consisted of a 24 inch diameter SDR 17 HDPE pipe (24 inch HDPE pipe), a 24 inch
<br />diameter Highway Grade POPE pipe (24 inch PCPE pipe), and a 4 inch diameter SDR 17
<br />HDPE pipe (4 inch HDPE pipe), placed in trench excavated 3 feet deep by 6 feet wide and
<br />bedded in Underdrain Pipe Backfill material (3/4 inch minus material). Underdrain Fill
<br />(12 inch minus) was then placed above the pipe trench, with a minimum cross sectional
<br />azea of 40 square feet. A minimum of 6 inches of Select Structural Fill was placed over
<br />the Underdrain Fill, and overlain with the Underdrain geosynthetics.
<br />During 1995 construction, it will be required that the "stubbed-T" Underdrain will be
<br />constructed along the Phase II Draw. However, for the stubbed T Primary Underdrain
<br />constructed for Phase II, only the 24 inch PCPE pipe will have to be installed and bedded
<br />in Underdrain Pipe Backfill. Therefore, the pipe trench dimension will be 4 feet wide, by
<br />3 feet deep to reflect change in number of pipes to be installed as part of the underdrain
<br />system. In addition, the Underdrain Fill would be placed 3 feet deep by 15 feet wide,
<br />which exczeds the 40 square foot cross sectional area criteria for the Underdrain Fill. This
<br />is illustrated in the attached detail.
<br />To summarize, the enhancement does not effect the integrity or intent of the underdrain,
<br />since it relates only to the piping and flow capacity required for the Phase II Pad area.
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