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  NWO-2017-01961-DEN
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NWO-2017-01961-DEN

Posted: 11/7/2017

Expiration date: 12/7/2017


Purpose

For purposes of definition under Section 404, the basic project purpose is stream channel improvement.  The overall project purpose is to establish a stable low-flow channel within Greenwood Gulch to improve conveyance through the project reach and reduce the flood risk to adjacent infrastructure.

           

Impacts and Mitigation

The project would result in permanent impacts along approximately 1,850 linear feet of Greenwood Gulch, which includes 0.033 acre of stream and 2.13 acres of wetland impacts.  Compensatory mitigation for permanent wetland and stream channel impacts is proposed at a 1:1 ratio, and consists of a combination of banking and on-site in-kind mitigation.  The proposed project would result in an increase of approximately 1,545 linear feet of stream channel within the project area. 

Following are the approximate quantities of fill that would be permanently placed within waters of the U.S., including wetlands:

 

  • 95 cubic yards of Type VL soil riprap

  • 719 cubic yards of Type M soil riprap

  • 60 cubic yards of Type VH soil riprap

  • 1,755 cubic yards of Type M void-filled riprap

  • Grouted boulder drop structure with 36-inch boulders (330 square yards)

     

    On-site mitigation will include establishing 1.92 acres of wetlands in the project area along the Greenwood Gulch channel.  The remaining 0.21 acre of wetland impacts will be mitigated through the purchase of credits from a Corps approved mitigation bank. 

    To accomplish the on-site mitigation component, the bank full channel section of the constructed/realigned channel of Greenwood Gulch would be planted with wetland sod, plugs, and native riparian seed.  Temporarily disturbed upland areas would be planted with a native seed mix following completion of construction.