MOFFAT COLLECTION SYSTEM PROJECT FINAL ENVIRONMENTAL IMPACT STATEMENT Executive Summary Photo provided courtesy of Denver Water. MOFFAT COLLECTION SYSTEM PROJECT FINAL ENVIRONMENTAL IMPACT STATEMENT Executive Summary Photo provided courtesy of Denver Water. TABLE OF CONTENTS Executive Summary ..................................................................................................................... ES-1 ES.1 Introduction ........................................................................................... ES-1 ES.2 Cooperating Agencies (EIS Chapter 6) ................................................ ES-2 ES.3 Public and Agency Participation (EIS Chapter 6) ................................ ES-3 ES.4 Purpose and Need (EIS Chapter 1) ....................................................... ES-3 ES.4.1 Purpose and Need Statement .................................................. ES-6 ES.5 Alternatives Analysis (EIS Chapter 2) .................................................. ES-7 ES.5.1 Screening................................................................................. ES-7 ES.5.2 Alternatives ............................................................................. ES-8 ES.6 Total Environmental Effects (EIS Chapter 4) ..................................... ES-10 ES.6.1 Reasonably Foreseeable Future Actions, Water- and Land-based Projects and Geographic Boundaries ................ ES-11 ES.6.2 Surface Water........................................................................ ES-13 ES.6.3 Water Quality ........................................................................ ES-18 ES.6.4 Channel Morphology ............................................................ ES-20 ES.6.5 Groundwater ......................................................................... ES-23 ES.6.6 Vegetation ............................................................................. ES-24 ES.6.7 Riparian and Wetland Areas ................................................. ES-24 ES.6.8 Wildlife ................................................................................. ES-24 ES.6.9 Special Status Species ........................................................... ES-24 ES.6.10 Aquatic Biological Resources ............................................... ES-25 ES.6.11 Air Quality ............................................................................ ES-26 ES.6.12 Recreation ............................................................................. ES-26 ES.6.13 Land Use ............................................................................... ES-26 ES.6.14 Visual Resources ................................................................... ES-27 ES.6.15 Socioeconomics .................................................................... ES-27 ES.6.16 Other Resources .................................................................... ES-28 ES.7 Moffat Project Effects (EIS Chapter 5) .............................................. ES-28 ES.7.1 Environmental Pool .............................................................. ES-28 ES.7.2 Surface Water........................................................................ ES-29 ES.7.3 Water Quality ........................................................................ ES-38 ES.7.4 Channel Morphology ............................................................ ES-40 ES.7.5 Groundwater ......................................................................... ES-43 ES.7.6 Geology ................................................................................. ES-44 ES.7.7 Soils....................................................................................... ES-45 ES.7.8 Vegetation ............................................................................. ES-46 ES.7.9 Riparian and Wetland Areas ................................................. ES-47 ES.7.10 Wildlife ................................................................................. ES-50 ES.7.11 Special Status Species ........................................................... ES-53 ES.7.12 Aquatic Biological Resources ............................................... ES-55 ES.7.13 Transportation ....................................................................... ES-56 ES.7.14 Air Quality ............................................................................ ES-57 ES.7.15 Noise ..................................................................................... ES-57 ES.7.16 Recreation ............................................................................. ES-58 ES.7.17 Land Use ............................................................................... ES-61 Table of Contents ES-i TABLE OF CONTENTS ES.7.18 Visual Resources .................................................................. ES-62 ES.7.19 Cultural/Historical/Paleontological Resources ..................... ES-65 ES.7.20 Socioeconomics .................................................................... ES-67 ES.7.21 Hazardous Materials ............................................................. ES-71 ES.8 Mitigation ........................................................................................... ES-71 ES.8.1 Explanation of Appendix M in the Final EIS ....................... ES-71 ES.8.2 Concurrent Planning Documents Relevant to Mitigation in the Final EIS ..................................................................... ES-72 List of Tables Table ES-1 Comparison of Average Annual Flows, Reservoir Outflows, and Diversions at Key Locations .......................................................ES-33 Table ES-2 Total Permanent Impacts to Wetlands, Other Waters of the U.S. and Riparian Areas ............................................................................ES-48 Table ES-3 Total Temporary Impacts to Wetlands, Other Waters of the U.S. and Riparian Areas ....................................................................ES-48 Table ES-4 Direct Impacts to Wildlife Habitat in Gross Reservoir Study Area by Alternative ...........................................................................ES-51 Table ES-5 Direct Impacts to Wildlife Habitat at the Leyden Gulch Reservoir Site ....................................................................................ES-52 List of Figures Figure ES-1 Public and Agency Participation Key Dates .......................................ES-1 Figure ES-2 Denver Water’s Collection System .....................................................ES-4 Figure ES-3 Total Annual Denver Water System Demand Versus Supply .............ES-6 Figure ES-4 Rivers Evaluated for the Moffat Project ............................................ES-17 ES-ii Table of Contents Executive Summary ES.1 INTRODUCTION In 2003, the City and County of Denver, acting by and through its Board of Water Commissioners (Denver Water) notified the United States (U.S.) Army Corps of Engineers (Corps) of its intent to apply for a Department of the Figure ES-1 Army Permit (Section 404 Permit), pursuant to Public and Agency Participation Section 404 of the Clean Water Act (CWA), to place Key Dates fill material in jurisdictional waters of the U.S., including wetlands. The fill would be for the construction of a water storage facility associated with developing additional water supplies. The Corps determined that an analysis of the significant natural and human environmental effects of the proposed Moffat Collection System Project (Moffat Project or Project) and reasonable range of alternatives was necessary to provide for full public disclosure and to aid in decision-making. The Proposed Action and action alternatives would result in direct impacts to wetlands and other waters of the U.S. The Proposed Action would result in 1.95 acres of permanent and 0.12 acre of temporary impact to wetlands, in addition to 3.53 acres of permanent and 0.49 acre of temporary impact to other waters of the U.S. This action requires authorization from the Corps under Section 404 of the CWA. This Environmental Impact Statement (EIS) was prepared in accordance with the National Environmental Policy Act of 1969, as amended, (NEPA) and the Corps’ regulations for implementing NEPA (33 Code of Federal Regulations [CFR] 325, Appendix B). This EIS has also been formulated to address the information requirements of the Section 404(b)(1) Guidelines (40 CFR 230). The Corps, Omaha District, Regulatory Branch, is the lead Federal agency responsible for preparing the EIS. The Corps is assisted by a team of third-party contractors led by URS Corporation, working under the direction of, and in cooperation with, the Corps in accordance with December 17, 1997 guidance from the Corps Chief of Engineers regarding preparation of an EIS. Figure ES-1 provides a graphic representation of the key public and agency participation dates for the Project. Information contained in the EIS serves as the basis for a decision regarding issuance of a Section 404 Permit. It also provides information for local and State agencies having jurisdictional responsibility for affected resources. Executive Summary ES-1 Executive Summary This Final EIS for the proposed Moffat Project was revised significantly based on comments and additional information received from agencies and the public since publishing the Draft EIS in October 2009. New studies were conducted for water quality, channel morphology, groundwater, riparian and wetland areas, aquatic biological resources, and socioeconomics. Although the Final EIS was updated in many areas in response to