Document Type: Supplemental EA- Administrative Record Index Field: Environmental Assessment Project Name: Bottom Ash Process Dewatering Facility SEA – Permanent Flow Management System Project Number: 2018-25 GALLATIN FOSSIL PLANT BOTTOM ASH PROCESS DEWATERING FACILITY PERMANENT FLOW MANAGEMENT SYSTEM FINAL SUPPLEMENTAL ENVIRONMENTAL ASSESSMENT Sumner County, Tennessee Prepared by: TENNESSEE VALLEY AUTHORITY Chattanooga, Tennessee December 2019 To request further information, contact: Ashley R. Farless, PE, AICP NEPA Compliance Tennessee Valley Authority 1101 Market Street Chattanooga, TN 37402 E-mail: [email protected] This page intentionally left blank Table of Contents Table of Contents CHAPTER 1 - PURPOSE OF AND NEED FOR ACTION ......................................................... 1-1 1.1 Introduction and Background ......................................................................................... 1-1 1.2 Purpose and Need ......................................................................................................... 1-4 1.3 Decision to be Made ...................................................................................................... 1-4 1.4 Related Environmental Reviews and Consultation Requirements ................................. 1-4 1.5 Scope of this Analysis .................................................................................................... 1-4 1.6 Public and Agency Involvement ..................................................................................... 1-5 1.7 Necessary Permits or Licenses ...................................................................................... 1-5 CHAPTER 2 - ALTERNATIVES ................................................................................................ 2-1 2.1 Description of Alternatives ............................................................................................. 2-1 2.1.1 Alternative A – No Action ................................................................................... 2-1 2.1.2 Alternative B – Closure of the Bottom Ash Pond, Construction of Process Water Basin(s) and Permanent Flow Management System ............................................................................................................... 2-1 2.1.3 Preferred Alternative from the 2017 Bottom Ash Dewatering Environmental Assessment ................................................................................ 2-4 2.2 Comparison of Alternatives ............................................................................................ 2-5 2.3 Identification of Mitigation Measures .............................................................................. 2-5 2.4 Preferred Alternative ...................................................................................................... 2-6 CHAPTER 3 - AFFECTED ENVIRONMENT AND ENVIRONMENTAL CONSEQUENCES .... 3-1 3.1 Air Quality ....................................................................................................................... 3-1 3.1.1 Affected Environment ......................................................................................... 3-1 3.1.2 Environmental Consequences............................................................................ 3-2 3.1.2.1 Alternative A – No Action ...................................................................... 3-2 3.1.2.2 Alternative B – Closure of the Bottom Ash Pond, Construction of a Process Water Basin(s) and Permanent Flow Management System ................................................................... 3-2 3.2 Vegetation ...................................................................................................................... 3-3 3.2.1 Affected Environment ......................................................................................... 3-3 3.2.2 Environmental Consequences............................................................................ 3-5 3.2.2.1 Alternative A – No Action ...................................................................... 3-5 3.2.2.2 Alternative B – Closure of the Bottom Ash Pond, Construction of Process Water Basin(s) and Permanent Flow Management System ................................................................... 3-5 3.3 Wildlife ............................................................................................................................ 3-6 3.3.1 Affected Environment ......................................................................................... 3-6 3.3.2 Environmental Consequences............................................................................ 3-7 3.3.2.1 Alternative A – No Action ...................................................................... 3-7 3.3.2.2 Alternative B – Closure of the Bottom Ash Pond, Construction of Process Water Basin(s) and Permanent Flow Management System ................................................................... 3-7 3.4 Threatened and Endangered Species ........................................................................... 3-8 3.4.1 Affected Environment ......................................................................................... 3-8 Final Supplemental Environmental Assessment i Table of Contents 3.4.1.1 Potentially Occurring Terrestrial Species .............................................. 3-8 3.4.1.2 Species Descriptions .......................................................................... 3-10 3.4.2 Environmental Consequences.......................................................................... 3-11 3.4.2.1 Alternative A – No Action .................................................................... 3-11 3.4.2.2 Alternative B – Closure of the Bottom Ash Pond, Construction of Process Water Basin(s) and Permanent Flow Management System ................................................................. 3-12 3.5 Surface Water and Wastewater ................................................................................... 3-13 3.5.1 Affected Environment ....................................................................................... 3-13 3.5.2 Environmental Consequences.......................................................................... 3-19 3.5.2.1 Alternative A – No Action .................................................................... 3-19 3.5.2.2 Alternative B – Closure of the Bottom Ash Pond, Construction of Process Water Basin(s) and Permanent Flow Management System ................................................................. 3-19 3.6 Groundwater and Geology ........................................................................................... 3-23 3.6.1 Affected Environment ....................................................................................... 3-23 3.6.1.1 Groundwater Quality ........................................................................... 3-24 3.6.1.2 Groundwater Use ................................................................................ 3-24 3.6.2 Environmental Consequences.......................................................................... 3-25 3.6.2.1 Alternative A – No Action .................................................................... 3-25 3.6.2.2 Alternative B – Closure of the Bottom Ash Pond, Construction of Process Water Basin(s) and Permanent Flow Management System ................................................................. 3-25 3.7 Wetlands ...................................................................................................................... 3-25 3.7.1 Affected Environment ....................................................................................... 3-25 3.7.2 Environmental Consequences.......................................................................... 3-26 3.7.2.1 Alternative A – No Action .................................................................... 3-26 3.7.2.2 Alternative B – Closure of the Bottom Ash Pond, Construction of Process Water Basin(s) and Permanent Flow Management System ................................................................. 3-27 3.8 Solid Waste and Hazardous Waste ............................................................................. 3-27 3.8.1 Affected Environment ....................................................................................... 3-27 3.8.2 Environmental Consequences.......................................................................... 3-28 3.8.2.1 Alternative A – No Action .................................................................... 3-28 3.8.2.2 Alternative B – Closure of the Bottom Ash Pond, Construction of Process Water Basin(s) and Permanent Flow Management System ................................................................. 3-28 3.9 Transportation .............................................................................................................. 3-30 3.9.1 Affected Environment ....................................................................................... 3-30 3.9.2 Environmental Consequences.......................................................................... 3-30 3.9.2.1 Alternative A – No Action .................................................................... 3-30 3.9.2.2 Alternative B – Closure of the Bottom Ash Pond, Construction of Process Water Basin(s) and Permanent Flow Management System ................................................................. 3-30 3.10 Noise ...........................................................................................................................