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<br />Cimarron Dredging Environmental Assessment <br /> <br />turbidity are associated with sediments from dredging operations}. The measurements could be <br />used to determine when dredging should cease. A table of trophic conditions could be <br />constructed that would allow for a determination of when turbidity became limiting. We could <br />also look at ways to determine how to manage the dredging process. We could also look at data <br />from other reservoirs to determine appropriate secci-disc depths. <br /> <br />Response: This comment was discussed in greater detail with USGS staff on September 6. 2001. <br />USGS does not expect turbidity to be a major concern as a result of the dredging project. In <br />consultation with CDOW. Reclamation was unable to identify at what level turbidity impacts <br />below Crystal Dam. Reclamation will continue to work with CDOW to monitor water quality <br />effects as a result of the dredging project. <br /> <br />'. <br /> <br />Reclamation will consider collecting turbidity measurements in Crystal Reservoir and the <br />Gunnison River below Crystal as part of its water quality monitoring program. Logistically, <br />using the secci disks is problematic because of limited access. <br /> <br />Comment 3: Sample Sites: Is the site at Crystal South tail bay downstream from the reservoir? <br />Why are you collecting data at the sites upstre:uTI from the Morrow Point footbridge') There is no <br />explanation for the rational behind the sampling network. The site and the Morrow Point <br />footbridge and downstream make sense. <br /> <br />Response: The Crystal South tail bay sampling site is located on the Gunnison River below <br />Crystal Reservoir. The sampling network was developed to monitor water quality changes for <br />this project and to collect baseline data for the proposed Morrow Point drawdown and trash rack <br />cleaning project that will occur in late 2002 or 2003. In discussions with the CDOW, sample <br />sites were selected so that Rec1amation could monitor water quality changes throughout the <br />Aspinall system and see how suspended sediments and other water quality parameters move <br />through the system. The Cimarron River was also included in the sampling network because it is <br />the largest contributor of sediment below Morrow Point and above Crystal. Water Quality data <br />to date is attached for reference in the Appendices. <br /> <br />Comment 4: If there is an impact of the turbidity of the reservoir and downstream. consider <br />dredging every other day to minimize the persistence of any effect. <br /> <br />Response: Dredging every other day is possible if turbidity becomes a problem. The frequency <br />could be even longer if appropriate. <br /> <br />Comment 5: If you are concerned with monitoring effects of the dredging downstream from <br />Crystal, a turbidimeter could be rented and installed at the Gunnison River below the Gunnison <br />Tunnel (or immediately downstream from the Crystal Reservoir) to provide real-time data for use <br />in decision making. Different secci-depth reading could be compared to turbidity data to <br />determine if dredging should continue. <br /> <br />30 <br />