Laserfiche WebLink
IRIS <br />MITIGATION AND DESIGN, INC. <br />Environmental Consulting <br />IRIS MITIGATION AND DESIGN, INC. <br />3450 W. 32nd Avenue, 2nd Floor <br />Denver, Colorado 80211 <br />Phone: 720 - 272 -1985 <br />bleisure @irismitigation.com <br />Lastly, we currently propose to install approximately 1,000 willow stakes upstream of the cutoff <br />wall in the previously undisturbed riparian area. This 0.09 acre area will revegetate and we will <br />plant approximately 40 riparian trees after Phase 2 construction for further riparian area <br />reconstruction. The upland areas around the cutoff wall will be restored after the wall is installed <br />(within a month) and the upland areas will be re- seeded and planted with upland trees and <br />shrubs. <br />Comment 5: That brings me to another concern. The upstream cutoff wall will largely dewater <br />the downstream reach. I know they are committing to irrigation of dewatered areas during the <br />project. It seems that since this may last 5 -10 years, there should be monitoring of these areas to <br />see if the dewatering /irrigation is having an adverse impact. I didn't see this described. I will <br />leave it to you to suggest what frequency and type of monitoring should take place. <br />On site we were told that the upstream cutoff wall would remain post project, probably notched <br />in some way to pass flows. But it will then be discharging alluvial water from upstream at the <br />surface. What impact will this have on alluvial groundwater downstream? I'm not sure any, but <br />it seems that there would at least be some effect during dry seasons and immediately downstream <br />of the cutoff wall. This potential impact (or reason why there isn't one) needs to be explained for <br />Phase 1 since this is when the wall is being permitted. <br />Response 5: The riparian corridor downstream of the proposed upstream cutoff wall will be <br />irrigated as proposed in the original BA packet. This stretch of riparian area will be monitored <br />during the growing season (mid May through September) each year until the creek flow is re- <br />established through this area. The stretch of creek will be monitored monthly through the <br />growing season through the establishment of one meter square plots along the corridor (10 plots <br />total). The plots will include at least one tree, several shrubs, and herbaceous understory as <br />feasible. Data will be collected on number of species, type of species, and inventory of health of <br />each species. The health of the trees, shrubs and understory will be assessed and photographed <br />over time. Any deterioration in the health or vigor of the plant species indicating possible dry <br />conditions will intensify irrigation efforts until the plants return to previous healthy conditions. <br />All data collected from the plots (including photographs) will be kept in an annual log for the <br />year. Yearly trends will be studied to determine whether irrigation efforts are sufficient for <br />riparian area health. Irrigation efforts will be adjusted annually based on these trends. <br />The Phase 1 cutoff wall will have minor impact on alluvial groundwater recharge downstream of <br />the cutoff wall once creek flow is restored back into the area (after Phase 3) for a variety of <br />reasons. The main reason is that the soil and underlying alluvium in this location is very <br />permeable and therefore quickly recharges. In addition shallow bedrock (6 -19 feet in depth) <br />ensures that the permeable alluvium will readily recharge surface discharge down into the <br />Schwartzwalder Mine Phase 1 Page 10 October 2011 <br />Response to USFWS Comments <br />