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High Density Residential Areas, Urban Outdoor Recreation Areas & Transportation Corridors

Status and Trend

Interpretation and Commentary

High Density Residential

Status: Somewhat Worse Than Target
Trend: Little or No Change
Confidence: Low

Urban Outdoor Recreation

Status: Somewhat Worse Than Target
Trend: Moderate Decline
Confidence: Low

State Route 28

Status: Somewhat Worse Than Target
Trend: Little or No Change
Confidence: Low

State Route 89

Status: Somewhat Worse Than Target
Trend: Little or No Change
Confidence: Low

State Route 207

Status: Somewhat Worse Than Target
Trend: Little or No Change
Confidence: Low

State Route 267

Status: Considerably Worse Than Target
Trend: Little or No Change
Confidence: Low

State Route 431

Status: Somewhat Worse Than Target
Trend: Little or No Change
Confidence: Low

Click to interpret these icons
  • Relevance - This indicator measures 24-hour noise levels in the High Density Residential and Urban Outdoor Recreation land use categories, and State Routes 28, 207, 267, and 431 transportation corridors in the Lake Tahoe Basin. Noise by definition, is “unwanted sound,” and is therefore a subjective reaction to acoustical energy or sound levels. Due to the rural nature of the communities and the pristine natural areas in the Lake Tahoe Basin, excessive noise levels have the potential to negatively impact community ambiance, one’s recreational experience and wildlife behavior. In recent years, visitors and residents of the Lake Tahoe Basin have expressed concerns about the decline in serenity of their community and their enjoyment of the outdoors due to excessive noise from sources such as on-highway vehicles, off-highway vehicles, over-snow vehicles, watercraft and aircraft(TRPA 2007c).In addition to existing federal, state, and local noise control regulations, an effort to address these noise level impacts, the Tahoe Regional Planning Agency adopted 24-hour noise Threshold Standards, or Community Noise Equivalent Levels (CNEL), for all land use categories, plan areas, and transportation corridors of the Basin.
  • Adopted Standards  - For the High Density Residential and Urban Outdoor Recreation land use categories and State Routes 28, 89, 207, 267 and 431 transportation corridors, noise levels shall not exceed a CNEL of 55 dBA.
  • Indicator - A-weighted Decibel (dBA). The A-weighted decibel measurement is used in evaluating the effects of environmental and industrial noise effects on human health.
  • StatusHigh Density Residential The High Density Residential land use category has fluctuated in and out of attainment since 1991 (Engineering Dynamics 1991; TRPA 1996, 2001). In 2011, an annual mean CNEL value of 52 dBA was measured, ranging from 45 to 62 dBA (TRPA 2011d). A status of “somewhat worse than target” was determined because it was 13% worse than the adopted Threshold Standard.
  • Status Urban Outdoor RecreationSince 1991,the Urban Outdoor Recreation category has also fluctuated in and out of attainment (Engineering Dynamics 1991; TRPA 1996, 2001, 2004). In 2011, an annual mean CNEL value of 50 dBA (range 41 to 59 dBA) for Urban Outdoor Recreation areas was measured (TRPA 2011d). A status of “somewhat worse than target” was determined because it was 7% worse than the adopted Threshold Standard.
  • Status – State Routes 28, 89, 207, 267 and 431- From 1991 to 2011, these transportation corridors were minimally sampled, reporting “non-attainment” at every sampling (Engineering Dynamics 1991; TRPA 1996, 2001). In 2011, annual mean CNEL for these corridors ranged from 56 to 69 dBA, with a single day value range of 56 to 70 dBA (TRPA 2011d). A status of “somewhat worse than target” was determined for State Routes 28, 89, 207, and 431 because they were 4%-22% worse than the adopted Threshold Standard. A status of “considerably worse than target” was determined for Highway 267 because it was 27% worse than the adopted Threshold Standard.
  • TrendHigh Density Residential – The change in CNEL for the High Density Residential land use category between 1991 and 2011 was +0.05 dBA/year or +0.1% indicating a trend determination of “little or no change.”
  • Trend Urban Outdoor Recreation – Since 1991,the change in CNEL for the Urban Outdoor Recreation land use category was +0.08% dBA/year or +0.01% indicating a trend determination of “little or no change.”
  • Confidence
    • Status - 1) Noise monitoring equipment was calibrated according to manufacturers’ specifications, 2) sampled land use units and locations within each land use category were randomly selected and 3) additional sampling effort was deployed in 2011. Because of these measures, confidence in the status was determined to be “moderate.”
    • Trend -  The confidence in the trend for the High Density Residential land use category is “low” for the analysis of 4 data points with a confidence of 21% and a P value of 0.79. The confidence in the trend for the Urban Outdoor Recreation land use category is “low” for the analysis of 5 data points with a confidence of 31% and a P value of 0.69. The confidence in the trend for the State Routes 28, 89, 207, 267 and 431 transportation corridors is “low” with a confidence range of 45-51% and a P value range of 0.49-0.56.
    •  Overall Confidence - The overall confidence for these land use categories and transportation corridors is “low” because there is “moderate” confidence in status and “low” confidence in trend.
  • Human and Environmental Drivers - Anthropogenic noise levels affecting these land use categories and transportation corridors are primarily generated from vehicles, roadway traffic, aircraft, and recreational activity(TRPA 2011c). Othersecondary anthropogenic noise influences include noise attributed to road construction and ambient Basin noise(TRPA 2011c). Natural events such as thunderstorms and wind influence noise levels as environmental drivers(TRPA 2011c).
  • Monitoring Approach – There is currently no established peer-reviewed monitoring plan or protocol for monitoring and evaluating the CNEL indicator. Historical monitoring consisted of gathering a single 24-hour sample per measured plan area. Threshold Standard attainment status was based on a single sample representing a land use type. In contrast to historic monitoring efforts, a more comprehensive CNEL monitoring effort was implemented in 2011. The 2011 monitoring approach was based on recommendations provided by a noise expert (Brown-Buntin Associates, Inc.) and included randomization of land use unit sampling within land use categories, and a replicated and intensified sampling effort that spanned multiple 24-hour periods to improve the characterization of variation in CNEL.
  • Monitoring Partners – Monitoring was conducted by TRPA with land access granted by U.S. Forest Service and the North Tahoe Public Utility District.

Links

 
  • Monitoring Plan
  • Conceptual Model

Map

click map for larger image

A map of High Density Residential, Urban Outdoor Recreation land use category areas, and transportation corridors of State Routes 28, 89, 207, 267, and 431, with monitoring locations (CNEL 55 dBA).

Trend Charts

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High and low single day CNEL values (bar endpoints), with annual mean CNEL in land use categories and transportation corridors having a Threshold Standard of CNEL 55 dBA from 1991 to 2011. Source:  TRPA noise monitoring data, Brown and Buntin Associates, Inc., Engineering Dynamics, Inc.

Additional Info

References

Additional Information

Last Updated on Friday, 26 October 2012 15:00