U.S. Highway 101 / State Route 46 West Interchange

District 05-SLO-101, PM 53 8, 1954.5
District 05-SLO-46, PM R21.5/R22.0
EA 05-451300
SCH Number 2008051102

Initial Study with Mitigated Negative Declaration / Environmental Assessment

Prepared by:
The State of California Department of Transportation

The environmental review, consultation, and any other action required in accordance with applicable federal laws for this project is being, or has been, carried out by the California Department of Transportation under its assumption of responsibility pursuant to 23 U.S. Code 327.

Highway 101 and State Route 46 West

December 2009

General information (PDF) about this document.

Table of Contents

Proposed Project

Chapter 1 (PDF)

  • 1.1 Introduction - 1
  • 1.2 Purpose and Need -7
  • 1.2.1 Purpose - 7
  • 1.2.2 Need - 9
  • 1.3 Alternatives - 11
  • 1.3.1 Build Alternatives - 11
  • 1.3.2 No-Build (No-Action) Alternative - 14
  • 1.3.3 Comparison of Alternatives - 14
  • 1.3.4 Identification of a Preferred Alternative - 23
  • 1.3.5 Alternatives Considered and Withdrawn - 25
  • 1.4 Permits and Approvals Needed - 27

Affected Environment, Environmental Consequences & Avoidance, Minimization & / or Mitigation Measures

Chapter 2 (PDF)

  • 2.1 Human Environment - 30
  • 2.1.1 Land Use - 30
  • 2.1.2 Growth - 40
  • 2.1.3 Farmlands - 42
  • 2.1.4 Community Impacts - 45
  • 2.1.5 Utilities/Emergency Services - 59
  • 2.1.6 Traffic and Transportation/Pedestrian and Bicycle Facilities - 61
  • 2.1.7 Visual/Aesthetics - 69
  • 2.2 Physical Environment - 81
  • 2.2.1 Hydrology and Floodplains - 81
  • 2.2.2 Water Quality and Storm Water Runoff - 85
  • 2.2.3 Geology/Soils/Seismic/Topography - 90
  • 2.2.4 Paleontology - 93
  • 2.2.5 Hazardous Waste Materials - 95
  • 2.2.6 Air Quality - 102
  • 2.2.7 Noise - 116
  • 2.3 Biological Environment - 129
  • 2.3.1 Natural Communities - 129
  • 2.3.2 Wetlands and Other Waters - 143
  • 2.3.3 Animal Species - 147
  • 2.3.4 Invasive Species - 151
  • 2.4 Cumulative Impacts - 153
  • 2.5 Climate Change under the California Environmental Quality Act - 156

Comments & Coordination

Chapter 3 (PDF) - 173

List of Preparers 

Chapter 4 (PDF) - 177

Distribution List

Chapter 5 (PDF) - 181