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�%COLORADO LEGACY LAND <br /> NNNIFTEARAL WSIO MARY TABLE <br /> COMMENT NO. COMMENT RESPONSE TO COMMENT <br /> Please include the approved permit boundary on any The requested revision has been made to Sheet 1. The area shown <br /> 1 maps/exhibits of the site(Sheets 1 and 3). on Sheet 3 is within the permit boundary,which is not shown at <br /> this scale. <br /> Letter-Drainage Design. The area draining to the contact between the NWRP and native <br /> The primary difference appears to be the proposal to convey slope is 4.1 acres. The runoff from this area will continue to flow <br /> runoff from the contributing area north of the North Waste Rock as it historically has; sheet flowing down the hillside until it <br /> Pile(NWRP)to Ralston Creek in a pipe rather than an open intersects the access road,then it will flow down the road and into <br /> 2 channel. The Table 1 summary does not address runoff draining Ralston Creek <br /> to the contact between the NWRP and native slope directly <br /> upgradient of the NWRP. This area is estimated to be on the <br /> order of five acres. Please discuss how direct runoff from this <br /> area will be conveyed past around the NWRP. <br /> Letter-Hydraulic Design. Most grade changes have been removed. The 2% slope at the <br /> No discussion is provided on the hydraulic performance of the bottom of the 30-inch pipe is intended to reduce water velocity and <br /> proposed pipe.There are considerable grade changes in the aid in energy dissipation. High velocities will prevent particles <br /> vertical alignment(varying between 29%and 2%).Is this from settling in the system. <br /> designed to function under pressure flow conditions or open <br /> channel flow? How will lodged tree branch or other debris affect The system is designed to work under open channel flow,however <br /> flow conditions? Where would surcharge resulting from a due to the possibility of a concurrent high tailwater elevation in <br /> plugged pipe go? A flow and energy gradient profile would be Ralston Creek and the energy loss in the bottom manhole, high <br /> very helpful. precipitation events could transition the system to pressure flow. <br /> A bolt-down lid at the lower manhole is specified on Sheets 3 and <br /> 4 to secure the manhole during this possible scenario. <br /> 3 Tree branches and large debris will not enter the pipe due to the <br /> trash rack at the headwall. Any sediment or debris that does enter <br /> the system be carried through the system. <br /> If outlet conditions (concurrent high flows in Ralston Creek) <br /> submerge the pipe and lead to pressure flow conditions,water will <br /> back up the 30-inch pipe; thus, the bolt-down lid. Water would <br /> continue to flow through the system and be contained within the <br /> pipe. <br /> See Sheet 4 for the Hydraulic Grade Line(water surface elevation) <br /> and Energy Grade Line in the pipe system. <br /> PAGE 2 OF 7 <br />