Pagosa Springs San Juan/Delores River Div 7 Response Letter

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r analysis,and in combination with goals and requirements expressed by the Town of Pagosa Springs and feedback from the public meeting 'that was held,the phase II design was created. The proposed improvements will provide a deep center channel that will act to pass sediment,woody debris and ice down the main channel. The drops in this main channel will create scour pools that have been shown to increase over-winter habitat. The elevated wings and added boulders will provide velocity barriers and large eddy habitat. Furthermore,the addition of rock structures, un-grouted scoured rock toe armoring, and un-grouted rock bank work will greatly enhance the interstitial habitat within the reach . These structures were chosen over more traditional structures,such as W- structures, because they are permanent,require no maintenance with the exception of minimal maintenance and adjustment after the first flow year, and because they represent a habitat and safety improvement over other forms of in-stream structures, An inspection of the new IJ-structure highlights its stability even afier the near record continuous high flows seen this spring. These structures will provide the recreational amenitylthat the Town of Pagosa Springs desires throughout this reach—for both fishing and boating. I would also like to address Mr. Dorsey's concern item by item: I. hem 11.1 71w use of concrete grout in streams is generally considered to negatively impact streams and associated aquatic life. The use of concrete grout to stabilize river features established a negative precedent. We do not wish to see the use of groat become commonplace. 777e cumulatiw impact on trout fisheries in rivers around the sate could be considerable, (We understand and support ACOE's interim policy that includes concrete as a toxin and limits its use in rivers without coffer dams in place.). would like to first note that this project is not a precedent for the use of concrete in the streambed. There are hundreds if not thousands of grouted dam,diversion, drop structures,bridge abutments, walls and other projects which have already usd concrete in the streanibed. In particular I would note the 2005 USACE project in Pueblo,CO in which similar grouted drop structures such as these were used to create a fish passage structure up a 14 foot concrete diversion dam. Mr. Dorsey's claim that the careful use of grout is"generally considered to negatively impact streams and associated life" lacks substantiation. I have discussed the use of grout in theses structures with Mr. Ken Jacobsen of the USACE in Grand Junction. He said there is no policy preventing the proper use ofgrout in these structures. Other recently USACE approved grouted drop structure projects include Clear Creek in Lawson, St Vrain River in Lyons,the Gunnison River in 1 Of note is that input from the public meeting was based specifically on improvements made during phase 1. Improvements suggested for phase II were based on the overwhelming support of this structure at this meeting. It is further of note that the primary recreational structures suggested for Phase U are situated only in highly urbanized areas. Other habitat structures are recommended in more passive areas. Mr.Dorsey's concern with regard to the grouted nature()lour rock structures are addressed later in this document.