Relevance

This indicator measures regional visibility and the distance that the human eye can see. It is measured by using a reconstructed light extinction (bext) value, which is derived from an equation that combines measured concentrations of several gasses and particles. The equation is corrected for humidity and natural “background” light scattering. Bext is summarized by “average visibility days” (50th percentile values) and “worst visibility days” (90th percentile values) for each year, followed by calculating the 3-year running average. This threshold standard has been adopted to protect regional visibility and air quality.

Human and Environmental Drivers

Particulate matter in the atmosphere is the primary driver of visibility impairment because of the optical properties and long retention times in the air. The main sources of particulate matter in the basin are residential and wildfire smoke, and entrained roadway dust. Effective motor vehicle tail pipe emission controls, residential wood combustion controls, appropriately managed prescribed burning, and road dust emission control aid in improving regional visibility conditions. There is uncertainty related to visibility condition in the future due to predicted increases in frequency and intensity of wildfires in the western U.S.

EIP Action Priorities

• Build and Enhance Trail Networks

  Bicycling, walking, and other forms of active transportation are important methods of travel that promote healthy lifestyles, improve air quality.

• Build and Enhance Transit Systems

  Comprehensive and coordinated bus and shuttle transit system that provides seamless around the lake service.

• Implement Prescribed Fire

  Prescribed fire and fire used for ecological benefit can reduce smoke exposure from large high intensity fires.

• Reduce Hazardous Fuels

  Reduce hazardous fuels and proactively manage forests to improve ecosystem resilience and reduce wildfire smoke.

EIP Indicators

• Miles of Pedestrian and Bicycle Routes Improved or Constructed

  Since 1997 EIP partners have collectively constructed or improved 198 miles of pedestrian and bicycle routes reducing the number of vehicle trips.

• Miles of Street Sweeping

  Since 2009 EIP partners have swept more than 91,000 miles of roadways within the Tahoe Basin reducing fine sediment particles from roadways entering the air and water.

• Non-Compliant Wood Stoves Removed or Retrofitted

  This EIP performance measure tracks removal of polluting wood stoves to reduce local air pollution for human and ecosystem health.

Example EIP Projects

• Purchase of High-Efficiency Sweepers - City of South Lake Tahoe

  To help increase sub-regional visibility, programs have been put in place for increased street sweeping such as the purchase of high-efficiency street sweepers.

Local and Regional Plans

• Climate Adaptation Action Portfolio

  Reducing emissions improves air quality.

• Tahoe Climate Resilience Action Strategy 2022

  Addressing emissions is core climate resilience strategy.

• Tahoe-Truckee Plug-in Electric Vehicle Readiness Plan

  This plan focuses on infrastructure for plug-in electric vehicles within the Tahoe-Truckee Region because they play a critical role in reducing the GHG emissions of vehicles.

Monitoring Programs

• Sub-Regional Visibility Monitoring

  Visibility monitoring data are collected, analyzed, and reported by the IMPROVE (national Interagency Monitoring of Protected Environments) network using nationally accepted protocols.

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