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d. Section Thru Spillway: The designed riprap layer is 1.5 thick on the embankment slope and for <br />some distance downstream before the thickness is reduced to 0.75 feet. Please provide a distance <br />dimension for each of the two riprap blanket thicknesses. <br />Response - Requested dimensions have been provided <br />e. Section Thru Spillway: No cross- sections perpendicular to the flow direction are provided. Please <br />provide lateral cross- sections through the embankment and through the run out downstream to <br />enable an evaluation of flow containment. <br />Response - A typical section has been added to the plans for the requested locations. <br />f. Diversion Dike, Section B -B; The bottom channel width is required to evaluate hydraulic stability. <br />Please provide a minimum bottom with dimension and a maximum side slope (e.g., 311:1V) on the <br />inside of the diversion dike. <br />Response - Dimensions have been added to the section. <br />g. Channel Data - Slope: The maximum slope is listed as 0.120 ft/ft. The Plan View shows a reach <br />with a 12.71% slope. This also appears to be the narrowest reach (refer to Comment 5.f). Please <br />revise the calculations to reflect the steeper design slope. <br />Response - Upon examination intended grading had not been properly annotated. Drawing labels <br />and calculations are now current. <br />h. Channel Data - Manning's n: The value of 0.028 appears too high for bare soil and too low' for <br />nprap. Please provide rationale for the selection of 0.028. Note flow velocities exceeding 5.0 fps <br />will require a discussion on armoring/erosion protection. <br />Response - Value of 0.028 was chosen from typical channel design charts and represents a earthen <br />channel with rubble sides/gravelly channel. This appeared to be the best fit among the <br />examples listed in the reviewed criteria as the dikes and berms will be constructed using neutral <br />mine waste rock <br />i. Detention Pond Volume: The columns are not labeled. DRMS assumes these columns are (from left <br />to right) "Elevation ", "Area (sq. ft.) ", "Cumulative Volume (cu. ft) ", and "Cumulative Volume (cu. <br />ft) ", respectively. Please label the columns. Also, DRMS assumes one cumulative volume is <br />obtained using average end area the other is obtained using the frustum of a cone or pyramid. <br />Please select only one volume to display to avoid confusion. <br />Response - Per DRMS request the headings have been added to the stage storage chart and the a set <br />of volumes has been eliminated <br />9. Exhibit LJ -3 - Designs, calculations and methodology. <br />a. Orepad Detention: The topography between the Orepad Pond and the decline is not clear. Please <br />provide some designs (e.g., minimum channel depth, width, side slopes, etc.) for the conveyance <br />structure to demonstrate this channel has the capacity to pass the 100 -year, 24 -hour peak flow to <br />the decline. <br />Response - Design dimensions and calculations have been added to the plan sheet <br />