PERMIT COMPLIANCE FILING Permittee: Permit Type: Project Location: Docket No: Permit Section: Date of Submission : Black Oak Wind,, LLC LWECS Site Permit Stearns County IP6853/WS-10-1240 and IP6866/WS-11-831 Site Permit Section 6.6 Noise December 20, 2016 [Revised] Black Oak Wind, LLC ( Black Oak ) respectfully submits this revised filing in compliance with Section 6.6 of the Site Permits issued for the Black Oak Wind Farm and Getty Wind Project: The Permittee shall submit a proposal to the Commission at least fourteen (14) days prior to the pre-operation compliance meeting for the conduct of a post-construction noise study. Upon the approval of the Commission, the Permittee shall carry out the study.. The study shall be designed to determine the operating LWECS noise levels at different frequencies and at various distances from the turbines at various wind directions and speeds.
FINAL POST-CONSTRUCTION NOISE STUDY METHODOLOGY Black Oak Getty Wind Farm Stearns County, Minnesota November 29, 2016 Prepared for: Black Oak Wind, LLC Prepared by: HDR Engineering, Inc. 701 Xenia Avenue South, Suite 600 Minneapolis, MN 55416
TABLE OF CONTENTS INTRODUCTION... 3 MEASUREMENT METHODS... 3 INSTRUMENTATION... 3 DATA COLLECTION... 4 MEASUREMENT LOCATIONS... 5 DATA PROCESSING AND REPORTING... 8 CONCLUSION... 11 TABLES Table 1. Summary of Monitoring Locations... 7 FIGURES Figure 1. Noise Monitoring Locations... 6 Figure 2. Time History... 9 Figure 3. Comparison of Spectral Sound Pressure Levels Onsite and Offsite... 9 Figure 4. Hourly L 10 Sound Levels vs. MPCA Noise Limits... 10 Figure 5. Hourly Time History vs. Wind Speed... 11 2
Introduction Black Oak Wind, LLC is constructing the Black Oak Getty Wind Farm in Stearns County, Minnesota. The generation facility is located south of Minnesota Route 28 and west of U.S. Highway 71. The Project will operate 39 Vestas V110 2.0 MW wind turbines. This postconstruction noise study methodology, prepared by HDR Engineering, Inc. (HDR), was designed in consultation with Energy Environmental Review and Analysis staff. The intent of the post-construction measurements is to determine the noise levels at different frequencies and at various distances from the operating turbines. The post-construction noise modeling is also intended to provide a basis for comparison with the noise modeling that was performed prior to construction. Additional information of interest includes the comparison of postconstruction noise levels to baseline (pre-construction) noise levels to determine the potential incremental increase in environmental noise associated with the Project and a comparison of measured noise to the Minnesota Pollution Control Agency (MPCA) noise regulations. Measurement Methods Equipment, measurement settings, and data collected for the post-construction noise measurements will be consistent with MPCA requirements outlined in the Measurement Procedure for Non-Impulsive Noise, designated by the MPCA as method NTP-1, and the Minnesota Department of Commerce, Energy Facility Permitting Guidance for Large Wind Energy Conversion System (LWECS) Noise Study Protocol and Report. The post-construction measurement methods will also be consistent with the pre-construction measurement methods described in HDR s Pre-Construction Noise Measurements Draft report dated May 13 th, 2016. Instrumentation The instrumentation to be used on the Black Oak Getty Wind post-construction noise monitoring includes the following: Digital sound level meters. Environmental microphones and preamplifiers, complete with large wind screens and bird spikes. Anemometers or other devices to measure wind speed at each location. A minimum of three Edirol R09 digital audio recorders (it is not necessary to continuously record audio at each location; the resolution of the measurement data will be sufficient to identify anomalies that need to be removed from the data). Pelican cases used to store the sound level meters and audio recorders. Large tripods to hold each microphone/preamplifier and each RM Young anemometer. The Black Oak Getty Wind post-construction noise measurements will utilize sound level meters with 1/3 octave band filters capable of measurement from the 12.5-Hz to 10,000-Hz bands. The sound level meters will meet the requirements of ANSI S1.4 Type 1 (precision). The sound level meters and analyzers are calibrated regularly by an independent laboratory using 3
standards traceable to the National Institute of Standards and Technology. The sound measurement systems, including microphones, preamplifiers, and sound level meters, are also adjusted to a reference level traceable to the National Institute of Standards and Technology, using a handheld calibrator meeting ANSI S1.40 and IEC 60942, Class 1 Sound Calibrator standards. The sound level meters are calibrated and adjusted in HDR s office prior to transportation to the measurement site. Calibration checks are performed in the field before the first measurement and after completion of the series of measurements. At least three measurement locations will include continuous or triggered audio recording. The audio files will allow the review of actual noise events that influenced noise monitoring results. Through this review, extraneous noise events may be identified. All measurement locations will also include anemometers to measure microphone-height wind speeds. The measured microphone-height wind speeds will identify periods with potential wind interference on the microphone. Data Collection The post-construction noise measurements will collect data as follows: The sound level meters will continuously integrate sound pressure level measurements and store data every hour on the hour. The microphones will be installed approximately five to six feet above the ground. The microphones will be placed at least 20 feet away from large reflective surfaces (i.e. buildings, walls, signs, etc.). The sound level meters will be programmed to store the un-weighted 1/3 octave band L eq and the A-weighted L eq 1, L 10, L 50, and L 90 2 on an hourly basis per the Minnesota Department of Commerce guidance protocol. The sound level meters will also store a more detailed time history, which will be used to calculate the C-weighted L eq, L 10, L 50 and L 90 on an hourly basis. The anemometers will measure the wind speed and direction at the microphone height. This data will be stored every hour on the hour. The digital audio recorders will continuously record an audio file of the entire monitoring duration. HDR proposes to selectively listen to the audio files. This may allow the exclusion of anomalous, spurious noise events due to precipitation, interference, disturbances (i.e. tampering with the equipment), etc. 1 The L eq represents a constant sound that, over the specified period (i.e. one hour), has the same acoustic energy as the time-varying sound. 2 The L 10, L 50, and L 90 are the noise levels exceeded 10 percent, 50 percent, and 90 percent of the hour, respectively. 4
Onsite meteorological data will be measured at hub height using a Project meteorological tower. Figure 1, below, shows the location of the meteorological tower that measures hub-height wind speeds. Operational data for wind turbines in use during the noise measurements will be included with the report. A log of precipitation events occurring during the measurement period will be obtained from the nearest weather station (which will be identified in the report). Monitoring will occur during a minimum of seven continuous days, and will begin within two weeks of the anniversary starting date of the pre-construction noise measurements per the Minnesota Department of Commerce guidance protocol. The pre-construction noise measurements began on September 14 th, 2015, so the post-construction noise measurements will begin between August 31 st and September 28 th of 2017. HDR expects winds to vary and produce a range of turbine operating conditions during the post-construction noise measurement period. The seven-day measurement duration may also be extended if it appears that a representative range of conditions did not occur. For example if weather patterns include periods of high wind or precipitation that last several days, then HDR will recommend that the measurement duration be extended. Similarly HDR will review the operational data and meteorological data to confirm that the study has measurement results in each wind speed bin. By virtue of their nature, unattended noise measurements have some inherent risks that also may merit extending the measurement period. The MPCA recommends that measurements be limited to periods without precipitation and when wind speeds at the microphone are below 11 mph to limit wind distortion. Therefore, HDR will process the measured data to identify the subset of data that fulfills this requirement; the post-construction noise monitoring report will present the raw unprocessed data and this subset of data. The data subset will be used in the remainder of the analysis. Measurement Locations Post-construction noise levels will be measured at five locations: four locations inside the Project area ( onsite ) and one outside the Project area ( offsite ). Figure 1 depicts the proposed monitoring locations. 5
Figure 1. Noise Monitoring Locations 6
Monitoring locations ML1, ML2, ML3, and BG5 were used in the pre-construction noise monitoring study. ML1 was predicted to experience the highest level of Project-related noise based on pre-construction noise modeling of wind turbine noise emissions completed in 2015 prior to the pre-construction noise measurements. ML1 was not the nearest residence to a proposed turbine, but it had the highest Project-related noise level due to proximity to several turbines. During the pre-construction noise measurements, it was determined the modeled residential receptor at ML1 was located on a barn instead of the house. The noise model was revised in 2016, which included relocating the residential receptor at ML1 from the barn to the house. This relocation reduced the modeled noise level by about 1 db, so the residential receptor at ML1 was no longer predicted to experience the highest level of Project-related noise. Instead, the highest predicted noise level at a residence is expected to occur in the southwest corner of the Project area between turbines 28 and 29. This location will be included in the post-construction noise measurements as ML4. Table 1 summarizes the selected monitoring locations including the distance from each monitoring location to the nearest turbine location; each monitoring location is located at a receptor (a residence). Table 1. Summary of Monitoring Locations Monitoring Location Parcel ID Distance to Nearest Turbine, m ML1 11.06688.0000 487 ML2 27.16603.0000 511 ML3 34.22843.0000 780 ML4 27.16699.0000 374 BG5 34.22833.0000 2295 Description Preconstruction monitoring location in the eastern portion of the Project area Preconstruction monitoring location in the western portion of the Project area Preconstruction monitoring location in the northern portion of the Project area Highest predicted Project sound level at a noise-sensitive receptor Preconstruction background location approximately 1.4 miles north of the nearest turbine The noise monitoring locations were chosen based on their distance from primary noise sources and representation of the rural Project area. Black Oak Wind, LLC will obtain permission from landowners to conduct monitoring at each of the proposed locations discussed in this filing. While it is anticipated that landowner permission will be granted, if any landowners object to hosting monitoring equipment, Black Oak Wind, LLC will provide the Department of Commerce with a map and explanation of equivalent substitute locations. ML1, ML2, ML3, and ML4 are representative of residences in different portions of the Project area. They are also representative of residences at varying distances and directions from turbines. Additionally, ML4 is representative of the predicted worst-case receptor. ML4 is predicted to experience the highest level of Project-related noise based on the pre-construction noise modeling of wind turbine noise emissions. 7
BG5 is representative of onsite residences, but without noise contributions from turbines. Measurements at BG5 and the four onsite measurement locations will be performed concurrently. Measured noise levels from BG5 will be compared to results from the preconstruction noise monitoring study to evaluate any potential changes in baseline noise conditions. Measured noise levels from BG5 and the pre-construction noise monitoring study will then be used to identify changes in noise due to the Project. Data Processing and Reporting The post-construction noise study for the Black Oak Getty Wind Farm will create two data sets: data set one will include the entire measurement duration and data set two will be the subset that is valid for comparison with the MPCA noise standards. Based on the requirements of the MPCA and the Department of Commerce, data set two will not include hours with: An average microphone-height wind speed equal to or greater than 11 miles per hour; A precipitation event; An average hub-height wind speed below the Vestas V110 2.0 MW wind turbine cut-in speed of 3 m/s or above the cut-out speed of 20 m/s; or, An extraneous noise event, such acoustical staff onsite for measurement equipment checks. Noise monitoring data will be expressed as un-weighted spectral data, and A-weighted and C- weighted L eq, L 10, L 50, and L 90. The noise monitoring data will also be compared to wind speed data to identify how measured noise levels vary with wind speed. The report will identify measurements of precipitation (in units of mm) that occurred during during post-construction noise measurmeents. Measurement data will be presented in the form of text, tables, and figures. The following are samples of the figures that will be used to present the monitoring data. Figure 2 depicts a sample of a detailed time history graph. A similar graph will be developed for data set one. Figure 2 presents the A-weighted and C-weighted hourly L eq in comparison to average wind speeds. 8
Sound Pressure Level, db 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00 0:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 9:00 10:00 11:00 12:00 13:00 Hourly Leq Wind Speed, m/s Figure 2. Time History 100 90 80 70 60 50 40 30 20 10 10 9 8 7 6 5 4 3 2 1 A-weighted, dba C-weighted, dbc Unweighted, db Wind Speed, m/s 0 0 Time Figure 3 is an example of how un-weighted spectral data will be presented on a 1/3 octave band basis. The 1/3 octave band analysis will be conducted for ML4 and BG5, which represent the residence predicted to experience the highest Project-related noise levels and the background measurement location, respectively. Figure 3. Comparison of Spectral Sound Pressure Levels Onsite and Offsite 80 70 60 50 40 30 20 Onsite Off-site 10 0 Frequency, Hz 9
Sound levels measured in the Project area will also be compared to the MPCA noise standards. Figure 4 is an example of the format that will be used to depict the hourly L 10 and L 50 in comparison to the MPCA daytime and nighttime noise standards. Figure 4. Hourly L 10 Sound Levels vs. MPCA Noise Limits Post-construction A-weighted and C-weighted hourly L 10, L 50, and L 90 data will also be compared to measured wind speeds using a format similar to Figure 5. The top of the vertical lines indicate the L 10 and the bottom of the vertical lines indicate the L 90. This figure depicts hourly sound distributions in comparison to average wind speeds. 10
00:00 01:00 02:00 03:00 04:00 05:00 06:00 07:00 08:00 09:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00 Sound Pressure Level, dba Wind Speed, mph Figure 5. Hourly Time History vs. Wind Speed 60 60 50 50 40 30 20 10 40 30 20 10 L10 L50 L90 Leq Wind 0 0 Hour The post-construction noise assessment report will also include a comparison of measurement results with calculated (modeled) noise levels. Conclusion The post-construction noise methodology is designed to quantify noise levels in the vicinity of the Black Oak Getty Wind Farm. The methodology was designed in consultation with Energy Environmental Review and Analysis staff. 11