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IRIS <br />MITIGATION AND DESIGN, INC. <br />Environmental Consulting <br />IRIS MITIGATION AND DESIGN, INC. <br />3450 W. 32 Avenue, 2nd Floor <br />Denver, Colorado 80211 <br />Phone: 720 - 272 -1985 <br />bleisure@irismitigation.com <br />Comment 4: Regarding impacts to the Preble's, to what extent will the cutoff wall <br />hamper /prevent movement of the mouse up and down stream? Given the road, grouted riprap <br />slope, etc. how will the mouse move through? This may relate what restoration of temporarily <br />impacted areas at the wall site will occur and how fast. Hopefully the boulders can be set in <br />grout and filled between with gravel /with dirt that can support vegetation. I hate grout to the top <br />if not necessary. Likewise riprap can be staked with willow. <br />Response 4: The cutoff wall itself should not hamper /prevent movement of the Preble's up and <br />downstream as the wall will be flush with what will be existing upland grade once installed. The <br />upstream side of the cutoff wall will have a concrete drop down into the riparian area and creek, <br />much as the existing concrete drop off now due to the existing culvert beneath the existing <br />unpaved road crossing of the creek. Although the unpaved road will remain open for on -going <br />mine related purposes, it will remain closed to outside access as it is part of the restricted mine <br />area. The road will not be used more than it has been historically used as the Phase 3 site <br />cleanup will be completed almost entirely downstream of the road crossing. <br />The unpaved road will not impact movement of the Preble's as it will be restored as an unpaved <br />road crossing and will be seeded with the native upland seed mix and mulched. A portion of the <br />road will be replaced with grouted boulders that extend downgradient into the creek. These <br />boulders will be 42" in size and will be grouted only one half to two thirds of the way up each <br />boulder. This will leave between 14" and 24" gaps between the boulders with no grout. We <br />propose to place soil between the boulders across the restored road access and down across both <br />sides of the channel. Boulders within the 10 foot wide channel bottom will not receive soil as <br />any creek flows above approximately 11 -12 gps will overtop the system and flow down the <br />channel. These flows are expected mainly in the spring but will flush any placed soil /seed <br />downstream. However, the gaps between boulders in this location will allow for invertebrate, <br />amphibian, reptile, and small mammal movement between boulders in the channel bottom. <br />The boulders which will have dirt placed in gaps (majority of the grouted boulder area) will also <br />be seeded with the native upland seed mix by broadcast seeding at twice the recommended rate. <br />Seeding the areas between the boulders will assist in revegetation of the grouted boulder area and <br />creation of a vegetated movement corridor for the Preble's and other species. <br />In addition, we propose to bury all riprap along the riparian area downstream of the grouted <br />boulders and within the upland area just downgradient of the cutoff wall. Buried riprap will have <br />6" of topsoil placed and be seeded /mulched or have erosion control fabric installed once seeded. <br />These areas will revegetate and allow for improved Preble's movement up and downstream. <br />Schwartzwalder Mine Phase 1 Page 9 October 2011 <br />Response to USFWS Comments <br />