NAPA RESOURCE CONSERVATION DISTRICT Pope Creek Weed Management Project Initial Study/Mitigated Negative Declaration December 2019 For accessibility assistance with this document, please contact the Napa County Resource Conservation District (NCRCD) at 707-252-4189, fax to 707-252-4219, or through the California Relay Service by dialing 711. This document includes complex figures and tables that may be difficult to interpret using an assistive device such as a screen reader. NAPA RESOURCE CONSERVATION DISTRICT Pope Creek Weed Management Project Initial Study/Mitigated Negative Declaration Prepared for: Napa County Resource Conservation District 1303 Jefferson Street, Suite 500B Napa, California 94559 Prepared by: Horizon Water and Environment, LLC 266 Grand Avenue, Suite 210 Oakland, California 94610 Contact: Ken Schwarz (510) 986-1851 December 2019 Horizon Water and Environment. 2019. Pope Creek Weed Management Project Initial Study/Mitigated Negative Declaration. December. (HWE 18.032) Oakland, CA. TABLE OF CONTENTS Chapter 1 Introduction .................................................................................................... 1-1 1.1 Introduction ................................................................................................... 1-1 1.2 Project Location ............................................................................................. 1-1 1.3 Intent and Scope of this Document ............................................................... 1-3 1.4 Organization of this Document ...................................................................... 1-3 1.5 Impact Terminology ....................................................................................... 1-4 Chapter 2 Project Description .......................................................................................... 2-1 2.1 Project Background ........................................................................................ 2-1 2.2 Project Purpose and Objectives ..................................................................... 2-1 2.3 Species Targeted for Vegetation Management and Control ......................... 2-2 2.3.1 Tamarisk ............................................................................................. 2-2 2.3.2 Arundo ................................................................................................ 2-2 2.3.3 Tree of Heaven ................................................................................... 2-3 2.3.4 Himalayan Blackberry ......................................................................... 2-3 2.4 Weed Management Strategies and Techniques ............................................ 2-3 2.4.1 Chemical Control ................................................................................ 2-4 2.4.2 Mechanical Control ............................................................................ 2-5 2.4.3 Biological Control................................................................................ 2-5 2.5 Implementation Strategy and Restoration .................................................... 2-6 2.5.1 Management Unit A ........................................................................... 2-6 2.5.2 Management Unit B ......................................................................... 2-21 2.5.3 Management Unit C ......................................................................... 2-21 2.5.4 Management Unit D ......................................................................... 2-21 2.5.5 Management Unit E .......................................................................... 2-22 2.5.6 Management Unit F .......................................................................... 2-22 2.6 Monitoring and Adaptive Management ...................................................... 2-25 2.6.1 Maintenance and Monitoring .......................................................... 2-25 2.6.2 Adaptive Management ..................................................................... 2-25 2.6.3 Timing of Work ................................................................................. 2-25 2.6.4 Staging and Access ........................................................................... 2-26 2.6.5 Best Management Practices ............................................................. 2-26 Pope Creek Weed Management Project December 2019 Initial Study/Mitigated Negative Declaration v Napa County Resource Conservation District Table of Contents 2.7 Equipment .................................................................................................... 2-38 2.8 Required Permits and Approvals ................................................................. 2-38 Chapter 3 Environmental Checklist .................................................................................. 3-1 3.1 Aesthetics ....................................................................................................... 3-5 3.1.1 Regulatory Setting .............................................................................. 3-5 3.1.2 Environmental Setting ........................................................................ 3-6 3.1.3 Discussion of Checklist Responses...................................................... 3-7 3.2 Agriculture and Forestry Resources ............................................................... 3-9 3.2.1 Regulatory Setting .............................................................................. 3-9 3.2.2 Environmental Setting ...................................................................... 3-10 3.2.3 Discussion of Checklist Responses.................................................... 3-11 3.3 Air Quality .................................................................................................... 3-13 3.3.1 Regulatory Setting ............................................................................ 3-13 3.3.2 Environmental Setting ...................................................................... 3-16 3.3.3 Discussion of Checklist Responses.................................................... 3-17 3.4 Biological Resources .................................................................................... 3-21 3.4.1 Regulatory Setting ............................................................................ 3-22 3.4.2 Environmental Setting ...................................................................... 3-24 3.4.3 Discussion of Checklist Responses.................................................... 3-25 3.5 Cultural Resources ....................................................................................... 3-33 3.5.1 Regulatory Setting ............................................................................ 3-33 3.5.2 Environmental Setting ...................................................................... 3-36 3.5.3 Discussion of Checklist Responses.................................................... 3-38 3.6 Energy .......................................................................................................... 3-43 3.6.1 Regulatory Setting ............................................................................ 3-43 3.6.2 Environmental Setting ...................................................................... 3-44 3.6.3 Discussion of Checklist Responses.................................................... 3-44 3.7 Geology, Soils, and Seismicity ...................................................................... 3-47 3.7.1 Regulatory Setting ............................................................................ 3-48 3.7.2 Environmental Setting ...................................................................... 3-49 3.7.3 Discussion of Checklist Responses.................................................... 3-50 3.8 Greenhouse Gas Emissions .......................................................................... 3-53 3.8.1 Regulatory Setting ............................................................................ 3-53 3.8.2 Environmental Setting ...................................................................... 3-54 3.8.3 Discussion of Checklist Responses.................................................... 3-55 3.9 Hazards and Hazardous Materials ............................................................... 3-57 Pope Creek Weed Management Project December 2019 Initial Study/Mitigated Negative Declaration vi Napa County Resource Conservation District Table of Contents 3.9.1 Regulatory Setting ............................................................................ 3-57 3.9.2 Environmental Setting ...................................................................... 3-58 3.9.3 Discussion of Checklist Responses.................................................... 3-58 3.10 Hydrology and Water Quality ...................................................................... 3-61 3.10.1 Regulatory Setting ............................................................................ 3-62 3.10.2 Environmental Setting ...................................................................... 3-64 3.10.3 Discussion of Checklist Responses.................................................... 3-65 3.11 Land Use and Planning ................................................................................. 3-71 3.11.1 Regulatory Setting ............................................................................ 3-71 3.11.2 Environmental Setting ...................................................................... 3-73 3.11.3 Discussion of Checklist