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3. STORM WATER MANAGEMENT PLAN FOR UPPER GRASSY VALLEY <br />The proposed arrangement of storm water management facilities for all expected <br />conditions is illustrated on Drawing Sheets 3 and 4. Sheet 3 shows the proposed <br />configurations of the Upper Grassy Valley basin in its current condition (Detail 1), after mining <br />(Detail 2), and after reclamation (Detail 3). Details of a fourth configuration are provided <br />(Detail 7) in which realignment of Upper Grassy Valley is proposed after the WHEX pit has <br />been backfilled. Sheet 4 includes details of the EMP Ponds, a schematic of the storm water <br />flow, profiles of the water ways, and design dimensions for the channels and ponds. <br />The conditions shown on Detail 1 (Existing Conditions) have been demonstrated by <br />SEDCAD computations, and by previous experience at the mine to have the highest potential <br />for generating sediment and runoff. The land -use conditions during mining (Detail 2) include <br />high proportions of rock -fill faces (Curve Number 50) where runoff is low, even while the top <br />of the stockpile may be highly compacted with mine trucks (Curve Number 90). The low - <br />runoff effect of stockpile areas has been historically proven during construction of the Squaw <br />Gulch Overburden Stockpile. Runoff at the toe of the embankment is generally nonexistent <br />in recent years after full development of the embankment. Five detention ponds were <br />constructed and often stored runoff during early years of the Squaw Gulch Stockpile <br />construction. The existing conditions are also most likely to create erosion during tree and <br />topsoil removal when soils are exposed and disturbed. <br />Runoff during and after he reclamation phase (Details 3 and 7) should also be less <br />than current conditions of land -use because reclamation will inherently include Best <br />Management Practices, all of which will result in lower excess precipitation (lower Curve <br />Numbers). Accordingly existing conditions are considered to be the best criteria for designing <br />the ponds and channels and have therefore been used to calculate the required pond <br />volumes. <br />Client: CC&V Gold Mining Co. 2/2/12 <br />Title: Storm Water Management, MLE2 Page 7 <br />