2005-01-03_REVISION - M1999120 (5)

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Ms. Lynn Mayer January 3, 2005 Page 8 Little Dry Creek will act as a drain on the west side of the azea where mounding would occur. The creek will intercept additional shallow groundwater from mounding and convey this water to the north and ultimately to the South Platte River. Little Dry Creek should be able to convey any additional water due to mounding without effects on the channel. This will naturally mitigate for impacts from mounding. There are no jurisdictional wetlands within the amendment azea that would be impacted by the proposed operation, so a Section 404 Permit is not required. There is a band along Little Dry Creek. Mining will not occur within 50 feet of Little Dry Creek, so that there will be no direct impacts to these wetlands. The wetlands are fed by shallow groundwater associated with the creek. The wetlands aze in a location where groundwater mounding is projected. The creek should intercept and convey excess groundwater to prevent ponding. A small rise in groundwater may still occur, but this should be beneficial to the wetlands. A wetter hydrologic regime will encourage proliferation of more obligate wetland species and reduce invasion by upland weeds It may also result in expansion of the wetlands. The lowering of groundwater to the north is not anticipated to have any impacts on the structural integrity of surrounding wells and surface water drainages. This is because of the relatively small amount of drawdown that will occur. Two wetlands occur in the projected groundwater shadow. One wetland is in a Swale immediately east of County Road 25 that is connected to the East Lateral of the Lupton Bottoms Ditch (see Drawing 5). The wetland is sustained by irrigation water in the East Lateral. Groundwater is projected to be reduced by 2 to 3 feet beneath the wetland with the projected effects from the amendment. This will not affect the wetland since it is sustained by surface water. This wetland may be considered "isolated" by the Corps since it is not directly connected to the South Platte River. This wetland is not unique and is typical of other wetlands in this reach of the South Platte River basin. The other wetland in the projected shadow is a small wetland in a side channel on the South Platte River. This wetland is located at or close to the baseflow level of the river and is sustained by the river. The small lowering of groundwater that is projected will not negatively affect this wetland. One area of cottonwood forest exists in the projected groundwater shadow (Drawing 5). Groundwater is shown to be lowered 2 to 2.5 feet in this area. The grove contains a low to moderate density of mature trees. No young cottonwoods or wetlands exist, so the roots for the trees tap into deeper groundwater. The grove is immediately adjacent to the river. Groundwater levels beneath the grove may be supported by the river. For these reasons, it is believed that the projected shadow will not negatively affect this cottonwood grove. #10 Effects of proposed operation on conveyance of water in ditches. Little Dry Creek runs along the west side of the proposed amendment area. No mining will occur within 50 feet of the creek. Slurry walls for the mining cells east of the creek will be