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I l I I I I I I ~- I I I I I I I I I I Page 3 Chunnel Committee Decembei 2, 199.J Wetlands We have spoken with the wetland consultant for Black Hawk about existing mapping. The existing wetland inventory has been quantified and provides a goal for reestablishing wetlands along the low flow channel. A wetland sub-consultant will be engaged during low flow channel design to coordinate with the landscape architect on plantings, species, etc. 404 Permit Futura has compiled and coordinated the 404 permit application with Sandra Laney of the Corps of Engineers. Background data has been accumulated along with graphic representations necessary for Corps processing. Additional interaction will soon be necessary with the Corps as processing continues. The Hydraulics Section of the Omaha Corps of Engineers Office will be involved in review at the request of the Tri-Lakes Project Office (Sandra Laney and Tim Carey). Hydraulics Section involvement is discussed in more detail under Peer/Colleague Technical Review, below. Hydrology Hydrology analysis, the initial step of all drainage projects was reviewed to determine the scope of design and to anticipate construction difficulties in this narrow, developing corridor. The design discharge recommended is the regulatory value related in the Owen Ayers study completed for Black Hawk in 1981 with a value of 2,400 to 2,600 cIs. FuIlJra had completed a North Oear Creek hydrology study for Gilpin County in 1993 which had a considerably smaller value for the l00-year flood. This was discussed with Becky Davidson early in the project to review the prudence of the lower value in light of theone,third lower construction cost. Ms. Davidson has since spoken with the Federal Emergency Management Agency about design discharge. As noted above, the existing regulatory value (higher value) is recommended for design since it provides a factor of safety . The lower hydrology value has been used as an indicator of snow melt peak flow. Snow melt hydraulics and sediment transport presents different Chunnel performance requirements which have been analyzed. Hydraulics and sediment transport have been analyzed at 500 to 2,200 cIs in 500 cfs increments. The low-flow hydrology study was based on several area stream gages, but concentrated on the following gages: 1. North Oear Creek near Black Hawk, drainage area of 52.2 square miles, four years