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Rob Zuber <br />Page 6 <br />October 14, 2015 <br />Please update Map 1013 to show all areas of Quaternary Alluvium within the proposed permit <br />area and comment on any differences in spatial extent between this layer and the layer <br />shown on Map 7A as Qv (valley fill deposits). <br />Rule 4.05.13 — Surface and Ground Water Monitoring <br />21. The text in Volume 15, Rule 4, Page 10, states that the alluvial groundwater monitoring well MC - <br />04 -01 "is additionally designated as a 'Point of Compliance" well for alluvial groundwater <br />monitoring purposes." This appears to be contradicted by later statements, and in any case MC - <br />04 -01 is not appropriately located to be a point of compliance since there is disturbance <br />proposed in the Collom Gulch drainage downgradient of MC -04-01. <br />Please update the text describing MC -04-01. <br />22. CCC has shown that there is the potential for activity permitted under PR -4 to negatively impact <br />the quality of alluvial groundwater in the Collom Gulch, Little Collom Gulch and Jubb Creek <br />drainages. Rule 4.05.13 (1) (b) requires that points of compliance be established, in addition to <br />other monitoring points required by the Division. <br />Please propose locations for alluvial groundwater points of compliance downgradient from <br />the area affected by the activity proposed with PR -4. <br />23. Five alluvial monitoring wells are proposed with PR -4. Their approximate locations are shown in <br />Figure 1 as pink symbols with green labels; the red polygon represents the approximate outline <br />of the proposed Collom pit. The completion information for these wells is provided in Exhibit 26, <br />Item 1, and is satisfactory. <br />No upgradient monitoring wells are proposed, since, as is explained in Volume 15, Rule 4, Page <br />14, shallow groundwater is not present upgradient of the proposed Collom pit. With this in <br />mind, impacts will be assessed relative to baseline data only. <br />The only proposed monitoring point on Little Collom Gulch (MLC -04-01) is located more than 3 <br />miles downgradient of the proposed pit. The time taken for affected water to travel between <br />the proposed pit and the MLC -04-01 may be roughly estimated using an equation for average <br />linear velocity, such as [3]: <br />Kdh <br />Ux nedl <br />Assuming: <br />• Hydraulic conductivity, K = 3 ft/day (ref. table 2.04.7-40) <br />• Hydraulic gradient, dh/dl = -0.04 (equal to the average surface gradient estimated from <br />map 1013 ((6540-7300)/18,500) <br />0 Effective porosity, ne = 25% <br />