Air Quality

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Air Quality

Breathing Freely and Seeing Clearly in the Lake Tahoe Basin

Air quality in the Lake Tahoe Basin is affected by both mobile and stationary sources of air pollution from within and outside the Basin. Air quality issues are important in the Basin because of down slope drainage winds and inversions that hold air pollution close to the surface of the land and lake. These unique conditions require some air quality standards in the Basin to be more strict than state or federal regulations. The objective of the Tahoe Regional Planning Agency´s (TRPA) Air Quality Program is to ensure that concentrations of pollutants that are harmful to human health are held below standards. In addition, the program focuses on visibility and atmospheric deposition processes that affect Lake Tahoe´s famed water clarity.

Air quality directly affects the health of humans and the environment, both indoors and outdoors, and in many different ways. Air pollutants cause negative health effects such as eye irritation and respiratory problems that can become severe. Air pollution can also damage plant leaves and impair photosynthesis for some species. Air quality is not only a health issue, it is also a scenic, economic and water quality issue. Air pollutants, like wood smoke, can stain buildings and homes with soot, create an ugly haze, and some can even erode rock building materials and structures because of their acidity. These impacts lead Congress to pass the Clean Air Act (CAA) in 1970.

The 1970 CAA gave the United States Environmental Protection Agency (EPA) the authority to create and enforce air pollution standards and set emission standards for mobile and stationary air pollution sources. The CAA also required that states meet Ambient Air Quality Standards set by the EPA. Since then, the CAA has been amended to strengthen standards, require State Implementation Plans, include pollutant reduction programs, update procedures, and voice transportation policy goals.

Mobile sources of air pollution, mainly motor vehicles, are one of the most significant sources of pollution in the Tahoe Basin. They emit carbon monoxide (CO), nitrogen oxides (NO_x), hydrocarbons (HCs), particulate matter (PM), and other pollutants.

Stationary sources of air pollution, mainly older wood stoves, emit more particulate matter (PM) and aerosols by using more wood than cleaner Environmental Protection Agency (EPA) approved wood stoves.

Residents of the Tahoe Basin can help reduce the amount of toxins released by wood stoves by burning only dry, seasoned wood and avoiding fresh wood, pine needles, pine cones and paper treated with dyes or metals. TRPA implemented a Wood Heater Retrofit Program in 1993 that requires all wood heaters in any home sold, transferred or conveyed in the Tahoe Basin meet EPA emission standards. Popular, clean alternatives to wood heaters are pellet and gas stoves.

Pollutants from both mobile and stationary sources have the potential to deposit into the lake by the force of gravity, and affect lake clarity. The rate of deposition is greater when a warm layer of air traps pollutants close to the surface of the lake, called a thermal inversion, because the pollutants are concentrated and have time during the inversion to settle out of the air. TRPA adopted environmental thresholds and indicators to monitor the amount of pollutants emitted by both sources of air pollution. Air quality stations are currently measuring the concentrations of pollutants at many locations in the Lake Tahoe Basin. There are many projects and studies being conducted and implemented in the Lake Tahoe Basin designed to reduce air pollution concentrations.

Sources:

		Draft TRPA 2003 EIP Update 
		Draft TRPA 2001 Threshold Evaluation - Chapter 2 Air Quality
		Clean Air Act

Indicators

AQ-1 Carbon Monoxide

Threshold - Carbon monoxide levels shall not meet or exceed the TRPA 8-hour 6.0 parts per million (ppm).

Indicator(s)- The indicative value for attainment of this standard is the second highest CO concentration that is read at the Stateline, CA station (ppm).

AQ-2 Ozone

Threshold- Ozone levels shall not exceed the TRPA 1-hour standard of 0.08 ppm.

Indicator(s)- Attainment is based on the number of 1-hour periods, which equal or exceed the federal, Nevada, or TRPA standard at any of the permanent monitoring sites (unitless), and the number of 1-hour periods that exceed the California standard.

AQ-3 Particulate Matter

Threshold- Particulate matter concentrations shall not exceed the California and Federal standards for 24-hour concentrations (50 and 150 µg/m3, respectively) and the annual average (30 and 50 µg/m3, respectively).

Indicator(s)- Attainment is based on the number of 24-hour periods exceeding the applicable federal or state standards at any permanent monitoring station (unitless) and the annual average PM10 concentration at any monitoring station (g/m3).

AQ-4 Visibility

Threshold- TRPA´s regional and sub-regional visibility standards shall not be violated. In addition, for regional and sub-regional visibility, wood smoke concentrations shall be reduced 15 percent below the 1981 levels for sub-regional visibility. Suspended soil particles shall be reduced 30 percent below the 1981 levels.

Indicator(s)- For regional visibility, visual range is calculated from aerosol data gathered at the D.L. Bliss State Park monitoring site. For sub-regional visibility, visibility is calculated from aerosol data gathered at the Lake Tahoe Boulevard station. For state visibility standards, visual range is calculated from nephelometer data collected at Bliss State Park and Lake Tahoe Boulevard for periods in which relative humidity is less than 70 percent (miles).

AQ-5 Traffic Volume

Threshold- There shall be a 7 percent reduction in traffic volume on the U.S. 50 corridor from the 1981 values.

Indicator(s)- The standard uses the average traffic volume from 4 p.m. to midnight from November through February. Traffic volumes on U.S. 50, recorded at a site immediately west of the intersection of Park Avenue in the City of South Lake Tahoe (SLT), include a count of both directions during an average day. TRPA selected this indicator because the threshold appears in TRPA Resolution 82-11, under the heading “carbon monoxide” and historically this has been the location of the only existing carbon monoxide hot spot in the region, which occurred during the winter months.

AQ-6 Wood Smoke

Threshold- Annual emissions from wood smoke shall be reduced 15 percent from 1981 levels.

Indicator(s)- There are currently no scientifically sound direct measurements for wood smoke; however, indicative aerosol constituents are used to analyze wood smoke trends.

AQ-7 Vehicle Miles Traveled

Threshold- Vehicle Miles Traveled (VMT) shall be reduced 10% below the 1981 levels.

Indicator(s)- Typically, VMT is calculated directly from a traffic model. However, for the purposes of the 2001 Threshold Evaluation, TRPA utilized the 1995 VMT estimate from the TranPlan traffic model, and applied a factor to account for actual increases in traffic volumes from 1995 through 1999. Actual current traffic volumes were closer to the 1995 TranPlan-generated traffic volumes than they were to the 2001 forecasted traffic volumes. A factor was then developed comparing the 1995 model-generated traffic volumes to the current actual volumes. This relationship was then applied to the 1995 VMT estimate to account for increase in traffic in that time period, and estimate the current year VMT.

AQ-8 Particulate Matter

Threshold- Dissolved Inorganic Nitrogen (DIN) load on Lake Tahoe from atmospheric sources shall be reduced by approximately 20 percent of the 1973-1981 annual average.

Indicator(s)- Load is calculated using the annual average concentrations of particulate NO3 at the Lake Tahoe Boulevard air quality monitoring station (....g/m3) and the annual average concentrations of nitrogen dioxide at a Stateline, NV monitoring station. This monitoring station was relocated in 1998; therefore the annual average concentrations from a Sandy Way, SLT station are used to determine attainment.

More information about air quality indicators from the TRPA 2001 Threshold Evaluation

Research

A goal of TIIMS is housing documents about the past, present and future environmental research conducted in the Lake Tahoe Basin. Scientific research conducted by organizations, agencies, and universities aims to detect sources of pollution and discover ways to monitor and ultimately eliminate their impacts. Ongoing research efforts collecting baseline data will help regulatory agencies establish regulations and develop limits and indicators designed to improve environmental health.

In the Basin, the Air Quality Working Group and the Visibility Group strive to increase and maintain communication and collaboration among air quality and transportation interests, and provide technical guidance to the Tahoe Regional Planning Agency (TRPA). The advisory groups identify air quality and transportation efforts that drive the implementation of research needed to meet the objectives of regulatory agencies. Also, these groups assist TRPA in assessing deficiencies in the air quality program´s research, threshold indicators, policies, and other current issues confronting the air quality program.

TRPA staff, in cooperation with the advisory groups, California Air Resources Board, Nevada Department of Environmental Protection, federal and state transportation agencies, local government jurisdictions, stakeholders, and the public, identifies air quality and transportation projects that support air quality programs. Projects are also identified by compiling elements of research and management documents like the Federal Transportation/Regional Transportation Plan for the Lake Tahoe Region (August 2000), the 1992 Regional Transportation Plan/Air Quality Plan, TRPA Community Plans, the Lake Tahoe Air Quality Research Scoping Document (2000), Bicycle Plans, Master Plans, and Environmental Impact Statements.

TIIMS is always searching for more documents to include in this section so please contact tiims@trpa.org with possible links to other air quality research.