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Mr. William T. Davis - 2 - June 7, 1989 It is recommended that the operator not place fixed structures or topsoil stockpiles within the anticipated flood plain of a 10 year-24 hour precipitation event in Engleville Gulch. The flood plain should be defined (See comments under Rule 2.04.7.2 this letter) and avoided in order to minimize the potential for unnecessary property loss or enforcement actions should a flood cause failure of sediment control facilities or destruction of topsoil stockpiles. It is mentioned in the narrative under Section 2.05.3(1) and (2) of the application that the building of a new access road to the TY towers in the south 1/2 of Section 29 is to occur after reclamation of the Phase 2 mining and completed independent of the permit. A clearer statement is required to tine effect that the road will not be moved until all surface coal mining reclamation obligations have been completed and the final inspection and procedures required by Rule 3.03.2 have been satisfied. Under this section, a road is proposed to access the sediment pond but is not illustrated on Exhibit P. All anticipated roads should be designated and illustrated. Designs should comply with Rules 4.03.1, 4.03.2, or 4.03.3 as appropriate. Paragraph 3 of this section of the application states no alteration or relocation of a natural drainageway is expected. This statement conflicts with the operator's apparent plan to mine the channel of Engleville Gulch. Differences between this and other statements in the application should be resolved. Rule 2.05.4 The operator must provide detailed designs and calculations to show the final Engleville Gulch Channel configuration and demonstrate its stability. These must include a post-mining longitudinal profile, post-mining channel cross sections, velocity and erodability calculations, riprap calculations if erosive velocities are expected, and peak flow calculations for 10-year-24 hour and 100 year-24 hour storm events correlated to channel and flood plain morphometry. - The statement on page 5 of Section 2.05.3(1) and (2) that'"all water generated within the pit areas will be channeled into the sediment pond" should be revised to indicate all disturbed area drainage will be routed thru a sediment control system as is required by Rules 4.05.2(1) and 4.05.2(4). Topsoil piles for example are considered disturbed areas whose drainage must also be controlled.