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Aircraft

Status and Trend

Interpretation and Commentary

Aircraft (80dBA Departures/Arrivals)

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

Click to interpret these icons
  • Relevance - This indicator measures noise originating from aircraft take-offs and landings at the City of South Lake Tahoe Airport. From the early 1960s to the early 2000s, Lake Tahoe Airport supported flights into and out of South Lake Tahoe from a variety of commercial airline companies. Over the years, commercial flights at the Lake Tahoe Airport have fluctuated with varying frequency with no commercial service occurring since 2001. Since 2001, the Airport has supported aircraft-related operations for one helicopter sightseeing business, occasional military training touch landing exercises, emergency services, and privately-owned recreational flights only. Aircraft generated noise is most frequently recorded during summer months (June through September) with most exceedances occurring during 2 special area events (i.e., annual celebrity golf tournament, annual air show). Single Noise Event Threshold Standards adopted by TRPA were established to protect quality of life for residents and visitor, and to reduce noise-related impacts to wildlife.
  • Adopted Standards  - During the hours of 8 a.m. and 8 p.m. single noise events generated by aircraft shall not exceed 80 dBA Lmax (maximum decibel level in a single event) for arrivals and departures. During the hours of 8 p.m. and 8 a.m., the single event standard shall not exceed 77 dBA Lmax for aircraft arrivals and departures.
  • Indicator - A-weighted Decibel (dBA).
  • Status – Between 2008 and 2010,The South Lake Tahoe Airport regularly provided quarterly and annual airport noise reports to TRPA (CSLT 2008; CSLT 2009; CSLT 2010). These reports documented the number of single noise events exceedances by aircraft recorded at any of the six Lake Tahoe Airport noise monitoring locations. Based on data from the Airport, single noise events for aircraft were out of attainment with the no-exceedance standard for each year noise monitoring was conducted by the Airport (2008-2010), recording 82 exceedance in 2008 (mean = 13.7/monitoring site), 218 exceedances in 2009 (mean = 36.3/monitoring site), and 200 exceedances in 2010 (mean = 33.3/monitoring site). The average daily per monitoring site rate of exceedances at sites monitored by the Airport was 0.037 exceedances per day (1 exceedance every 26.7 days) in 2008, 0.099 exceedances per day (1 exceedance every 10 days) in 2009, and 0.091 exceedances per day (1 every 10.9 days) in 2010. Aircraft noise monitoring conducted by TRPA at an additional site outside the Airport monitoring program from 2009-2011, observed 3 exceedances in 2009, 7 exceedances in 2010, and 5 exceedances in 2011(TRPA 2011c). The average daily rate of exceedances at the site monitored by TRPA was 0.086 exceedances per day (1 exceedance every 11.7 days) in 2009, 0.171 exceedances per day (1 exceedance every 5.8 days) in 2010, and 0.085 exceedances per day (1 every 11.8 days) in 2011. Overall, the exceedance rate for the Airport averaged 0.095 exceedances per day or 1 exceedance every 12.8 days (equal to 35.8 days/year). Based on the most current results from TRPA monitoring efforts (2011), noise standards were exceeded on average 29.4 days/year or 6.8% of the days within a year), the Region was determined to be “somewhat worse than target.”

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  • Trend Trend in overall exceedance rate was determined to be “moderate decline” based on combined data collected at Barton Beach and Airport sites (2008 to 2011). A simple linear regression test indicated that trend in exceedance rate calculated from airport monitoring effort showed an increasing trend of 0.59/day/year, however, this trend was not statistically significant (Airport - R2=0.638, P = 0.411). There was no trend in exceedance rate recorded at the Barton Beach site (R2=0.25, P=0.667). The trend in overall average exceedance rate (exceedance rate averaged over all monitoring sites between 2008 and 2011) indicated an increase in exceedance rate of 0.021/day/year. However this was not statistically significant (R2=0.352, P=0.406) probably due to small sample size (n=4 years) and inter-annual variation in exceedance rate.

Confidence

  • Status – There is “moderate” confidence in the current status because although TRPA data were collected according to methods prescribed in TRPA’s Shorezone Noise Monitoring Program (and reviewed by a noise expert), procedures for the Airport Monitoring Program are different than those used by TRPA. TRPA noise monitoring equipment is regularly calibrated, and sample design and effort is documented (TRPA 2009).
  • Trend – The confidence in the trend in overall exceedance rate for all sites combined was determined to be “low” because the R2 value was less than 0.5 and the P value was greater than 0.4 per rules established for this evaluation (see Methodology chapter).
  • Overall Confidence - The overall confidence was determined to be “low” because there was low confidence in the trend determination.
  • Human and Environmental Drivers - The primary factors influencing single noise event exceedances are aircraft type and frequency of flight(California Department of Transportation 2007). Additional factors influencing aircraft noise levels include wind, temperature, cloud cover, fog, topography, vegetation and man-made barriers such as homes and other buildings. Thermal inversions, a common occurrence in the Basin(TIMMS 2011a), have the same effect on noise as does cloud cover (California Department of Transportation 2007).
  • Monitoring Approach – Lake Tahoe Airport monitored noise at six sites in the vicinity of the Airport (see map above) following an approved monitoring protocol. In order to match noise events to aircraft operations, radio transmissions between air traffic controllers in the air traffic control tower are matched to the noise event by date and time. All exceedances are documented and categorized in quarterly and annual noise reports to TRPA. The Barton Beach aircraft noise monitoring site was located in the shorezone of Lake Tahoe, approximately 0.2 miles from Lake Tahoe Airport. While the Airport monitoring sites generally have the ability to document aircraft noise on a year-round basis, data recorded at the Barton Beach site was limited to June through September, sampling a total of 135 days (approximately 3,240 hours). All exceedances at the Barton site were individually reviewed and analyzed by a trained noise technician.
  • Monitoring Partners – City of South Lake Tahoe and TRPA. The California Tahoe Conservancy provided access to their lands for monitoring.

Links

 
  • Monitoring Plan
  • Conceptual Model

Map

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A map of South Lake Tahoe Airport (dark north - south line) relative to noise monitoring sites (numbered dots), and TRPA's aircraft noise monitoring site at Barton Beach (red marker).

Trend Charts

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Overall average number of aircraft generated single noise event exceedances/day (exceedance rate) reported by City of South Lake Tahoe Airport (2008 to 2010), and at Barton Beach measured by TRPA (2009 to 2011). Overall exceedance rate ranged from 0.037/day (1 exceedance every 26.7 days) in 2008 to 0.171 (1 exceedance every 5.8 days) in 2010. Source: City of South Lake Tahoe Airport, TRPA noise monitoring data.

Additional Info

References

Additional Information

Last Updated on Friday, 26 October 2012 15:33