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Mr. Darry Ferguson -3- February 18, 1993 1. Division Ditch No. 1 - since the gravel pit will mine through this ditch, it must be relocated and redesigned for the appropriate storm event. 2. Verify that the East Collection Ditch can handle any additional runoff associated with the 33 acres of new disturbance from the gravel pit operations, if any. 3. Portions of the West Collection Channel are within the boundaries of the gravel pit operations and may be disturbed. Additionally, portions of the 33 acres to be disturbed will flow into the ditch, therefore, the ditch designs will have to be reevaluated and the ditch changed as necessary. 4. The permanent channel realignment will have to be redesigned for the 3.75 inch 100 year event. 5. The Division cannot find the calculations to derive flow for 30.0 cfs and 43.75 cfs for the West Fill and East Fill Downdrains. Please provide this information and update if necessary. 6. verify that Sediment Pond No. 2's emergency spillway can safety pass the 25 year event storm of 2.80 inches and that there will still be one foot of freeboard above level of the increased flow. If not, please submit new designs. 7. Since Pond 1 will receive an additional 33 acres of disturbed flow from the gravel pit operations, and due to the changes in the event storms, please recalculate all design parameters for Pond 1. Additionally, according to the Pond 1 as built drawings, the north end of the pond has an elevation o 6790.2 and the elevation of the emergency spillway rock channel is 6789.5 Even without water flowing, there is not 1 foot of freeboard above the emergency spillway as required by the regulations. Please address this matter as well during the redesign of Pond 1. The Division is aware that once the pit becomes operational, that water to the pond will be controlled by pumps, however, until the pit is actually retaining water the pond must completely contain the 10 year event and safely pass the 25 year event with 1 foot of freeboard above the 25 year event level. 8. The sediment control map does not adequately show how water flowing off of the explosives pad reaches pond 2. Please clarify this.