2019-04-03_REVISION - C1981038 (5)

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1313 Sherman Street, Room 215, Denver, CO 80203 P 303.866.3567 Please provide a quantitative analysis (such as a SEDCAD model ) or a qualitative discussion to show that the profile of the reconstructed channel will remain stable. Potential elements of the discussion could include:  A description of the channel bottom. For example, if the channel is bedrock, there is no potential issue with bed erosion.  Examples of where this approach has worked in other drainages. This could include details such as the slope of the other drainage, documentation showing that flows are similar to East Roatcap Creek, and documentation that the other drainage incurred large events without failure. The plan for the reconstructed East Roatcap Creek must be in line with Rule 4.05.4(4), which address restoration of stream channels after diversion (in this case the diversion was a culvert). As this rule states, the channel and floodplain dimensions need to approximate the premining configuration and blend with the undisturbed drainage above and below the reclaimed reach. If little or no documentation is available regarding premining conditions, the adjacent reaches should pro vide an acceptable proxy. 2. It appears that the East Roatcap Creek Channel Profile that is drawn on the revised version of Map 8A-19 is only the endpoints of the channel reach. Please provide a more detailed profile showing elevati ons every 100 feet (at least). Map 8A-19, revised 3/14/2019, is adequate. However, as BRL addresses item No. 1 (above), additional detail may be needed on this map.. 3. BRL submitted a letter from the U.S. Army Corps of Engineers with the TR64 application for inclusion in Volume 8A. Based upon this letter, the Corps of Engineers approved a stream channel reconstruction plan that includes 1000 cubic yards of riprap. However, BRL’s December 5, 2018, adequacy response to the Division states that riprap will not be placed in the channel reconstruction. Has the Corp of Eng ineers approved this change to the NWP50? Please provide documentation that the Corps pf Engineers has approved that change to the plan. BRL provided a copy of the approved U.S. Corps of Engineers permit no. SPK-2017- 00894 with the March 19, 2019. Submittal of this approved permit addresses the Division’s concern.