DRAFT ENVIRONMENTAL ASSESSMENT Pipestem Dam
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DRAFT ENVIRONMENTAL ASSESSMENT Pipestem Dam Safety Modification Study Stutsman County, North Dakota U.S. Army Corps of Engineers Northwestern Division Omaha District TABLE OF CONTENTS 1.0 INTRODUCTION .................................................................................................................... 4 1.1 Project Location .................................................................................................................... 4 1.2 Project Description................................................................................................................ 5 1.3 Dam Safety Risk Management ............................................................................................. 7 1.4 Purpose and Need for the Federal Action ............................................................................. 8 1.5 Authority ............................................................................................................................... 8 1.6 National Environmental Policy Act Scoping ........................................................................ 8 2.0 ALTERNATIVES................................................................................................................... 10 2.1 Alternative Development .................................................................................................... 10 2.1.1 RMP 2A - Stepped Chute Structure with Stilling Basin .............................................. 11 2.1.2 RMP 2B - Stepped Chute Structure with Stilling Basin (Lowered Spillway Channel)11 2.1.3 RMP 3 - Stepped Chute Structure with Stilling Basin and Grade Control Structures . 12 2.1.4 RMP 4 - Stepped Chute Structure with Stilling Basin and Concrete/RCC Lining ...... 13 2.1.5 RMP 6 - Nonstructural/Operational Measures ............................................................ 14 2.2 Alternatives Carried Forward ............................................................................................. 14 2.2.1 No-Action Alternative ................................................................................................. 15 2.2.2 Refined RMP 2A.......................................................................................................... 15 3.0 ENVIRONMENTAL ANALYSIS ......................................................................................... 19 3.1.1 Climate and Climate Change ....................................................................................... 19 3.1.2 Geology ........................................................................................................................ 20 3.1.3 Air Quality ................................................................................................................... 21 3.1.4 Water Quality ............................................................................................................... 21 3.1.5 Wetlands ...................................................................................................................... 22 3.1.6 Vegetation .................................................................................................................... 24 3.1.7 Fisheries ....................................................................................................................... 25 3.1.8 Wildlife ........................................................................................................................ 26 3.1.9 Threatened and Endangered Species ........................................................................... 27 3.1.10 Cultural Resources ..................................................................................................... 32 3.1.11 Recreation .................................................................................................................. 32 3.1.12 Socio-Economics and Environmental Justice ............................................................ 33 3.2 Cumulative Impacts ............................................................................................................ 35 4.0 COMPLIANCE WITH ENVIRONMENTAL LAWS AND REGULATIONS .................... 37 Pipestem DSMS Draft EA U.S. Army Corps of Engineers April 2019 Omaha District i 5.0 REFERENCES ....................................................................................................................... 40 List of Figures Figure 1.1: Pipestem Dam Vicinity Map ........................................................................................ 4 Figure 1.2: Pipestem Dam Location Map ....................................................................................... 5 Figure 1.3: Pipestem Dam Project Features .................................................................................... 6 Figure 1.4: Looking down the spillway from near the Reservoir ................................................... 6 Figure 1.5: Downstream end of spillway where it drops into the Pipestem channel ...................... 7 Figure 2.1: RMP 2A: Stepped Chute Structure with Stilling Basin ............................................. 11 Figure 2.2: RMP 2B – Stepped Chute Structure with Stilling Basin (Lowered Spillway Channel) ....................................................................................................................................................... 12 Figure 2.3: RMP 3 – Stepped Chute Structure with Stilling Basin and Grade Control Structures ....................................................................................................................................................... 13 Figure 2.4: Stepped Chute Structure with Stilling Basin and Concrete/RCC Lining ................... 14 Figure 2.5: Refined RMP 2A Conceptual Plan View ................................................................... 16 Figure 2.6: Refined RMP 2A Chute Structure and Stilling Basin Conceptual Profile ................. 17 Figure 2.7: Refined RMP 2A Left Training Dike Conceptual Cross Section .............................. 17 Figure 2.8: Proposed Stockpile and Haul Road Location ............................................................. 18 Figure 3.1: Wetlands near Pipestem Dam ..................................................................................... 23 Figure 3.2: Range of the Piping Plover in North Dakota .............................................................. 28 Figure 3.3: Whooping Crane Sightings in North Dakota ............................................................. 29 List of Tables Table 1.1: Pipestem Dam downstream communities ...................................................................... 8 Table 2.1: Final Array of Risk Management Plans....................................................................... 10 Table 3.1: Stutsman County 2017 Population .............................................................................. 33 Table 3.2: Stutsman County 2017 Racial and Ethnic Composition.............................................. 34 Table 3.3: Stutsman County 2017 Gender and Demographics ..................................................... 34 Table 3.4: Stutsman County 2017 Income and Poverty Levels .................................................... 35 Table 3.5: Past, Present, and Foreseeable Actions........................................................................ 35 Pipestem DSMS Draft EA U.S. Army Corps of Engineers April 2019 Omaha District ii List of Acronyms BA Biological Assessment CEQ Council on Environmental Quality cfs Cubic Feet per Second DSMR Dam Safety Modification Report DSMS Dam Safety Modification Study DSOG Dam Senior Oversight Group EA Environmental Assessment EIS Environmental Impact Statement ER Engineer Regulation ESA Endangered Species Act FONSI Finding of No Significant Impact FRM Flood Risk Management FWAC Future Without Action Condition IDF Inflow Design Flood IEPR Independent External Peer Review IES Issue Evaluation Study IRRM Interim Risk Reduction Measure LPD Local Project Datum NEPA National Environmental Policy Act O&M Operation and Maintenance OMRR&R Operation and Maintenance, Repair, Replacement, and Rehabilitation NDGFD North Dakota Game and Fish Department NEPA National Environmental Policy Act PA Periodic Assessment PAR Population at Risk PED Preconstruction Engineering and Design PFM Potential Failure Mode PFMA Potential Failure Mode Analysis PMF Probable Maximum Flood QRA Quantitative Risk Assessment RMP Risk Management Plan SPRA Screening for Portfolio Risk Analysis SQRA Semi-Quantitative Risk Assessment STRL Societal Tolerable Risk Limit TRG Tolerable Risk Guideline TSP Tentatively Selected Plan USACE U.S. Army Corps of Engineers USBR U.S. Bureau of Reclamation USFWS U.S. Fish and Wildlife Service WAPA Western Area Power Administration WCM Water Control Manual WRDA Water Resources Development Act Pipestem DSMS Draft EA U.S. Army Corps of Engineers April 2019 Omaha District iii 1.0 INTRODUCTION The U.S. Army Corps of Engineers (USACE), Northwestern Division, Omaha District has prepared this draft Environmental Assessment (EA) to evaluate the potential environmental, cultural, and socioeconomic impacts of alternatives based on the Pipestem Dam Safety Modification Study (DSMS). The purpose of the DSMS is to identify and recommend a Risk Management Plan that reduces risk of erosion of the emergency spillway. This EA has been prepared in accordance with the National Environmental Policy Act (NEPA) of 1969 and the Council of Environmental Quality’s Regulations (CEQ) (40 CFR 1500-1508), as reflected