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• annual precipitation. Evapotranspiration rates in the region are relatively high <see <br />Tab 7, Hydrologic Description). The infiltration rate of precipitation through the loamy <br />soils and overburden, based on permeability races, is estimated to be slow to moderate- <br />Slow infiltration rates are common for this area and for this climate since the majority <br />of recharge to local aquifers occurs from the gradual infiltration of snowmelt water. <br />Overburden and topsoil handling, reconditioning, and revegetation methods outlined in iab <br />21 (Minesoil Reconstruction) and Tab 22 (Reveget ation Plan) will maximize the potential <br />for establishing reclaimed areas that yield infiltration rates and capacities equal to or <br />greeter than premining soil hydraulic conditions. Since the texture of the replaced <br />topsoil is generally loam to clay loam, the infiltration rate through [he topsoil will be <br />slow to moderate. Deep ripping of final graded spoil where severe compaction exists, <br />followed by topsoil placement and disking or direct haulage of topsoil where practicable <br />will enhance the infiltration potential of the reclaimed materials. <br />Significant ground water discharge to mining pits will be removed by pumping the water to <br />those sediment ponds designed to have the prescribed minimum volume for the 10-year, <br />• 24-hour storm event. Design criteria for the ponds is described in Tab 13 (Facilities), <br />and it includes plans of storage for additional volumes pumped from pits or sumps. <br />Maintenance of available storage capacity in the ponds involves dewatering and sediment <br />removal. <br />Ground Yater Monitoring. Peabody, in conjunction with the USGS, began ground water <br />monitoring at Yoast in the summer of 1980. Additional monitoring wells were installed in <br />1990. Currently [here are 56 ground water moni [oring wells at the Yoast complex. <br />Complete details of ground water monitoring are described in Tab 15, Hydrologic <br />Monitoring Program. Plans [o monitor the extent and magnitude of any mining impacts on <br />the ground water system are described in detail in Tab 18, Hydrologic Reclamation Plan. <br />Cround water monitoring wells will be maintained for the life of the mining operations or <br />until such time as [he CM LRD may agree that they are no longer necessary. AlL ground <br />water monitoring installations will be removed upon completion of the postmining <br />hydrologic monitoring phase of the Hydrologic Monitoring Plan unless they are approved <br />for postmining land uses. <br />• All ground eater date collected from monitoring wells in each future water year will be <br />3 <br />