tahoemonitoring.org

  • Increase font size
  • Default font size
  • Decrease font size
Home People Soundscape

Low Density Residential & Rural Outdoor Recreation Areas

Status and Trend

Interpretation and Commentary

Low Density Residential

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

Rural Outdoor Recreation

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 Low-Density Residential and Rural Outdoor Recreation land use categories 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, the Tahoe Regional Planning Agency adopted 24-hour noise Threshold Standards, or Community Noise Equivalent Levels (CNEL), for all land use categories and plan areas of the Basin.
  • Adopted Standards  - For the Low Density Residential and Rural Outdoor Recreation land use category noise levels shall not exceed a CNEL of 50 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.
  • StatusLow Density Residential The Low Density Residential land use category has fluctuated in and out of attainment since 1991 (Engineering Dynamics 1991; TRPA 1996, 2001, 2004). In 2011, an annual mean CNEL value of 52 dBA was measured, ranging from 45 to 58 dBA (TRPA 2011d). A status of “somewhat worse than target” was determined because it was 16% worse than the adopted Threshold Standard.
  • Status Rural Outdoor RecreationSince 1991,the Rural Outdoor Recreation land use category has reported “non-attainment” for 3 sampling periods (Engineering Dynamics 1991; TRPA 1996, 2001). In 2011, an annual mean CNEL value of 49 dBA (range 48 to 54 dBA) for Rural Outdoor Recreation areas was measured (TRPA 2011d). A status of “somewhat worse than target” was determined because the indicator was 8% worse than the adopted standard.
  • TrendLow Density Residential – The change in CNEL for the Low Density Residential land use category between 1991 and 2011 was +2.4 dBA/year or +0.5% indicating a trend determination of “little or no change.”
  • Trend Rural Outdoor Recreation – Since 1991,the change in CNEL for the Rural Outdoor Recreation land use category was +0.01% dBA/year or +0.01% indicating a trend determination of “little or no change.”

Click here for more information...

  • Confidence
    • Status - Even though 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 to improve inferences about the population of these land uses, and 3) additional sampling effort was deployed in 2011, a documented and peer-reviewed protocol for CNEL monitoring does not exist. Consequently, the confidence in the status was determined to be “moderate,” and the spatial and temporal characterization of CNEL across these land use types.
    • Trend -  The confidence in the trend for the Low Density Residential land use category is “moderate” for the analysis of 5 data points with a confidence of 82% and a P value of 0.18. Resulting from the analysis of 4 data points, the confidence in the trend for the Rural Outdoor Recreation land use category is “low” with a confidence of 2% and a P value of 0.98.
    •  Overall Confidence - The overall confidence for the Low Density Residential land use category is “moderate” because there is a “moderate” confidence in both status and trend. The overall confidence for the Rural Outdoor Recreation land use category 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 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 randomized 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 the U.S. Forest Service.

Links

 
  • Monitoring Plan
  • Conceptual Model

Map

click map for larger image

A map of Low Density Residential and Rural Outdoor Recreation land use category areas in the Basin, with monitoring locations (CNEL 50 dBA).

Trend Charts

You need to upgrade your Flash Player
 
High and low single day CNEL values (bar endpoints), with annual mean CNEL in land use categories having a Threshold Standard of CNEL 50 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 Wednesday, 19 September 2012 14:16