Final Report South Fork Road Corridor Plan January 2021 OR Benton 482(1) Prepared for: Prepared by: IDIQ Contract No. DTFH7015D00002L Western Federal Lands Task Order No. 690565720F000007 Highway Division South Fork Road Corridor Plan, OR Benton 482(1) TABLE OF CONTENTS 1 INTRODUCTION AND BACKGROUND ............................................................................................................................................ 1 1.1 Study Area ............................................................................................................................................................................ 1 1.2 Historical Construction and Improvement Projects ............................................................................................................ 3 1.2.1 Current and Planned Projects .......................................................................................................................................... 3 1.2.2 Existing Plans and Regulations ......................................................................................................................................... 3 2 TRANSPORTATION SYSTEM .......................................................................................................................................................... 5 2.1 Physical Features and Characteristics .................................................................................................................................. 5 2.1.1 Hydraulics ......................................................................................................................................................................... 5 2.1.2 Bridges ............................................................................................................................................................................. 7 2.1.3 Culverts .......................................................................................................................................................................... 10 2.1.4 Maintenance and Operations ........................................................................................................................................ 12 2.1.5 Roadway Surfacing ......................................................................................................................................................... 12 2.1.6 Access Points .................................................................................................................................................................. 12 2.1.7 Right of Way ................................................................................................................................................................... 12 2.1.8 Utilities ........................................................................................................................................................................... 14 2.1.9 Pedestrian and Bicycle Facilities .................................................................................................................................... 14 2.1.10 Recreational Opportunities ........................................................................................................................................ 15 2.2 Geometric Road Conditions ............................................................................................................................................... 15 2.2.1 Design Criteria ................................................................................................................................................................ 16 2.2.2 Horizontal Alignment ..................................................................................................................................................... 16 2.2.3 Vertical Alignment ......................................................................................................................................................... 17 2.2.4 Sight Distance ................................................................................................................................................................. 17 2.2.5 Clear Zone ...................................................................................................................................................................... 19 2.3 Traffic Control .................................................................................................................................................................... 19 2.4 Traffic Conditions ............................................................................................................................................................... 19 i South Fork Road Corridor Plan, OR Benton 482(1) 2.5 Safety ................................................................................................................................................................................. 20 2.5.1 Safety Trends, Contributing Factors, and Crash Clusters ............................................................................................... 23 2.6 Other Vulnerabilities .......................................................................................................................................................... 25 3 ENVIRONMENTAL SETTING ........................................................................................................................................................ 29 3.1 Physical Environment and Resources ................................................................................................................................ 29 3.1.1 Land Ownership and Land Use....................................................................................................................................... 29 3.1.2 Soil Resources and Prime Farmland ............................................................................................................................... 29 3.1.3 Geologic Hazards ............................................................................................................................................................ 30 3.1.4 Surface Waters ............................................................................................................................................................... 30 3.1.5 Groundwater .................................................................................................................................................................. 33 3.1.6 Floodplains and Floodways ............................................................................................................................................ 33 3.1.7 Wetlands and Waters of the U.S. ................................................................................................................................... 34 3.1.8 Hazardous Substances ................................................................................................................................................... 34 3.1.9 Air Quality ...................................................................................................................................................................... 34 3.1.10 Noise .......................................................................................................................................................................... 34 3.2 Biological Resources ........................................................................................................................................................... 36 3.2.1 Vegetation ...................................................................................................................................................................... 36 3.2.2 Fish and Wildlife ............................................................................................................................................................. 37 3.2.3 Threatened and Endangered Aquatic Species ............................................................................................................... 37 3.2.4 Threatened and Endangered Terrestrial Species ........................................................................................................... 40 3.2.5 Other Species of Concern............................................................................................................................................... 40 3.3 Social and Cultural Resources ............................................................................................................................................ 41 3.3.1 Demographic and Economic Conditions ........................................................................................................................ 41 3.3.2 Recreational Resources .................................................................................................................................................. 42 3.3.3 Cultural and Historic Resources ..................................................................................................................................... 42 3.3.4 Visual Resources ............................................................................................................................................................ 43 ii South Fork Road Corridor Plan, OR Benton 482(1) 4 Economic Drivers and Future Economic Activity and Effects Considered