2013-01-25_REPORT - M1992069 - Laserfiche WebLink

Home Browse Search

2.0 Requirements Special Condition G of the originally issued permit stated that the "wetlands must be determined to be viable and self - sustaining by the Corps of Engineers" and that "the criteria for success is the dominance of native herbaceous wetland species ". Although this language does not appear in Condition G as changed in the permit amendment, this is the basis upon which compensatory mitigation for this project is being evaluated to determine success. Evaluations of completed mitigation areas appear in Appendix 1, Evaluation of Wetlands, by Walsh Environmental Scientists and Engineers, dated January 17, 2012. 3.0 Summary Data Summary data and photos are included in Appendix 1. 4.0 Maps Figure 2 of Appendix 1 shows the location of the project site and the final constructed compensatory wetland mitigation areas, upland and pond areas. 5.0 Conclusions and Recommendations As noted above and in Appendix 1, the long -term effects of the June 15, 2010 flood event on the developing wetlands are still unknown, particularly when coupled with additional pit inundation in 2011. As flood conditions worsened again in June 2011 due to significant run- off and heavy rain, City of Greeley and Boyd Freeman Ditch Co. diverted flood water from the river through the ditch and into the F Street site in order to prevent further damage to the F Street site as well as surrounding and downstream properties. This controlled diversion did not have the severe impact of the 2010 flood but it did fill both ponds and inundated Area A wetland to water levels higher than would be expected under normal conditions when groundwater in the area stabilizes to pre - mining levels. In early August, 2011, Boyd Freeman Ditch Co. began pumping down the water level at the site in order to allow repair of the ditch and slope damage that had occurred in 2010. This work was completed early in 2012 and water levels are at or near what they were prior to the 2010/2011 flood events. With continued de- watering at the adjacent mining operation north of this site, it is not expected that the water level will increase again until those dewatering activities cease. While some mitigation areas of the site have been negatively impacted by these events, it appears that other areas of the site may have benefited from these flood events; however, any long -term impacts or benefits not only remain uncertain but are likely to change again as pre- flood conditions return due to the dewatering activities discussed above. Until the site Aggregate Industries -WCR 4 F Street Mine Site - 2011 Annual Report (File # 199280589) ■