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_ check dams, repair of existing check dams, rip rap, adjustment of diversion ditch entries, or construction of additional diversion ditches above the permanent drainageway which is eroding. Limited segments of select drainageways may have rip-rap placed as a preventative measure, in conjunction with the repair program. The exception to the usual permanent drainageway repair program involves the channel improvements established as a result of the Postmining Topography Permit Revision. Six channels have been designated for improvements. These channel segments are denoted on Map 28-3, Existing and Potential Permanent Drainageway Locations. The specific design criteria for the channels are explained in further detail within the Postmining Topography Permit Revision. In general, the repaired channel segment will include an upstream and downstream transition area at the points where the repaired channel will course into the existing permanent drainageway. All channel repair areas will be lined with a granular filter before rip-rap is applied. Rip-rap will consist of rock ranging from 27 to 6 inches spherical diameter. The ratio of the rock • sizing is dependent on the particular channel being repaired. Repair involving permanent channels will be completed in conjunction with the usual rill and gully repair program. All work will be finalized prior to October 31. A seventh channel segment has been designated for improvement near the Overburden Stockpile #1, below the junction of PG 61-1a and PG 9/10-1 to a point above Pond A. The location of the repair area is shown on diagram TR 93-35 on page 28-101a). The repair area will be re-configured, lined with a granular filter, and have rip- rap placed. Rip-rap will consist of rock ranging from 3-15 inches in diameter, with rock sizing dependent upon the distribution type being used. •TR 93-35 28_~D Revised 6/22/93