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• Itpound~ent Leakage The MLRD has expressed concern that excessive leakage will occur recirculating pond. Some leakage is inevitable. However, it ap) will be minimal. It is anticipated that the pond bottoms will be self-sealing. The fines and sediments will settle out of the mie drop to the pond floor. The existing material that was removed i bottoms was laboratory tested and Eound to be a low plasticity c] type which typically exhibits low permeability. Permeability tee conducted on the material, since it had already been disturbed. I this disturbance, lab tests will not yield a reliable approximate will occur in the field. • Operating Level/Freeboard The maximum operating level of the mine operations will be maint three feet below the crest of the pond embankment. Three feet o substantially more than is required to contain the 5-year, 6-hou from the area tributary to the pond embankment. However, the th figure is held to be reasonable in view of embankment stability, and emergency surcharge reasons. As demonstrated in a prior rep amount of runoff over the 150 acre contributory xatershed above is approximately 1.1 acre feet in a 5-year, 6-hour storm event. estimated 800 foot by 200 foot water surface area, the storm eve less than one foot of depth in the ponds, leaving over two verti freeboard. ONSITE DRAINAGE MLRD has expressed concern that not all of the mine slte will ac to the recirculating ponds. A slope study was performed which v all drainage form the mined area in Phase I will flow into the 1' Topography considerations make it virtually impossible to have t. permit area drain into the ponds, and it only necessary to contr the disturbed areas. RunoFE from the disturbed area will be der ponds. When the latter stages of the mine plan are reached, new probably will be required and they will be sized and sited at th Minor sedimentation ponds will be used to collect runoff xaters necessitated by the topography. EIVEH FLOODING MLRD has expressed concerns that embankments in the mine site ma endangered from the 25-year flood of the Middle Fork of the Sout River. As stated in a previous report, the river has a 33.3 squ watershed. This was calculated from the USGS 1:250,000 scale ma includes all areas tributary to the South Platte from its crossi Highway 9 and just south and east of Alma. The 25-year flood wa regression analyses developed by the United States Geological Su :rom the gars that it essentially water and •om the pond iy (CL) of a :s were not cause of ~n of what ned at least freeboard is storm runoff e Eoot ave action t, the e mine area even the occupies 1 feet of drain that entire runoff from tad to the time. be Platte e mile ing and under based on a er. The 25- 3