2021-12-29_PERMIT FILE - M2021009 (9)

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38 for additional details on plant growth medium. Deep organic litter composed of pine needles and tree debris does exist in isolated and north facing areas between the ground surface and shallow solid bedrock. Therefore, the permeability potential into the bedrock is limited. When removed and where possible, this surficial broken bedrock and forest litter material will be directly placed on the graded surfaces of WRL providing both coarse rock and growth medium, will be temporarily stored as reclamation materials on the processing pad, or will be used as backfill material following mining. 8. Page G-4 (middle of page) discusses "the channel bottom created by the embankment slope where it intercepts the natural grade on either side." The applicant should explain why this "channel"is not a designed ditch. This explanation should include estimated flows using the SCS Method or other method used in standard practice of stormwater engineering. Alternatively, designs for WRL side ditches (including hydrology and hydraulics calculations) should be included in the application, and these structures should be shown on map G-2 and other applicable maps. The WRL slope, in its entirety, was designed to act as a steep channel and thus the rock cap size was selected using the PADER method of selecting riprap in an armored channel. This was done using SEDCAD software; the appropriate output reports from SEDCAD are included in the revised Appendix G-1. Exhibit G figures show a typical cross section of the WRL slope to communicate the design approach. Appendix G-1 also contains flow data generated using the NRCS Technical Revision-55 Urban Hydrology for Small Watersheds methodology. Peak discharge was calculated using the Graphical Peak Discharge approach in the NRCS methodology. 9. map G-1 contains a statement that the "quarry floor drains offsite via road." Given this, more details for the road drainage at the south end are required. If appropriate, include flow calculations, a design for a roadside ditch and any other related structures, and a discussion on how this flow will be managed to prevent erosion on the undisturbed area adjacent to the road. Please refer to the response to question 49 of the Division's Preliminary Adequacy Review. Additionally, the revised permit narrative and Exhibit C maps provide more detail regarding hydrologic structures. 10. A text box on map G-2 states that the riprap for the buttresses at the bottom of the WRL was sized for 100-year flows. However, Exhibit G does not provide calculations for riprap size or for other design parameters for these buttresses. The applicant needs to provide this information. The riprap and WRL SEDCAD design reports can be found in Appendix G-1. Additionally, the revised permit narrative and Exhibit C maps provide more detail on riprap size determinations. 11. On map G-2 there appears to be an error with symbology. The buttress on the east side of the WRL is indicated, but there is no symbol for a buttress on the west side. Reference to a buttress has been removed. December 2021 32 Lewicki&Associates