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<br /> <br />and commends the applicant for their intentions of preserving and revitalizing jurisdictional <br />wetlands and riparian zones/vegetation within and adjacent to the proposed permit area. In <br />response (and in conformance with Rule 6.4.5(1)), the Division requests that the operator <br />consider and respond to the following recommendations: <br />A) Discharging of alluvial groundwater captured from dewatering operations if done in a manner <br />simulating "flood irrigation" to the wetlands/riparian zone may help recharge these azeas more <br />effectively than discharging directly to St. Vrain Creek from one or several discharge points. The <br />location of the discharge point(s) could be several or multiple locations at the fringe of the <br />wetlands/riparian zone rather than at the Creek. This would be particularly beneficial toward <br />maintaining the health of the existing wetlands/riparian habitats during critical times of the year <br />(April-June) when the water table would naturally be at or near the surface. (The applicant has <br />stated on page l7 that in an unaltered creek system, periodic flooding regenerates cottonwood <br />communities by scouring the bare mineral soils and simultaneous prolonged high water level at <br />the time of Cottonwood seed dispersal). <br />B) To be effective, a tree monitoring program should include such details as how the trees will be <br />evaluated (parameters), when will they be evaluated (frequency), what are the conditions that <br />characterize the trees as being "stressed", and how will mitigation measures be applied, ie: how <br />much water is needed to relieve the stress and for what length of time will the water be applied. <br />Also, the monitoring program should be designed to detect early signs of tree stress as opposed to <br />signs of tree "shock" when they may not be able to recover even with significant mitigation <br />measures. <br />C) Peizometers, if placed in strategic locations and monitored at regular intervals, may be very <br />beneficial in detecting significant fluctuations in the water table due to dewatering operations and <br />may help identify sensitive locations requiring mitigation. Baseline water level measurements <br />would certainly help characterize the hydrologic conditions needed in order to preserve the <br />existing wetland/ripazian vegetation. <br />D) Based on the aquifer characteristics, maximum depth of excavation expected, maximum rate <br />of dewatering or drawdown expected, and maximum area to be dewatered at any one time, the <br />applicant should be able to predict a cone of depression for each of the phases to be mined which <br />will define the lateral and vertical extent of hydrologic impacts expected due to dewatering. <br />Such a prediction can be used to help define strategic locations for monitoring points and can <br />also be used to help define whether multiple dischazge points to the wetland areas/riparian zones <br />might be needed rather than a single or a few dischazge point to St. Vrain Creek. <br />E) Tn the unfortunate event of tree mortality, a commitment to replace dying or dead trees at a <br />ratio of at least 1:1 (2:1 preferred) will help ensure preservation of the existing woody vegetation. <br />3. The applicant states on pages l3 & 14 that Aggregate will install a dewatering trench around <br />the area to be mined before mining commences, and that this water will be pumped into a settling <br />pond and then discharged into St. Vrain Creek. In accordance with Rules 6.4.4(c)&(f) the <br />Division requests that you provide a revised copy of the Mine Plan Map to show the location(s) <br />