Shiloh III Draft EIR Volume II Part 4

LT3

#5 #6

Figure 3: Location of Long Term measurement site LT3 in the western region of the project area along with numbers assigned to each residence considered minute increments over the course of the measurements. At the time the sound level meters were installed, the wind was gusting to about 2.5 to 5 m/s and most WTG’s in the vicinity of the sites were operating. Similar conditions were observed when the meters were removed on Tuesday, the 17th.

Measurements at the LT1 site were at a location about 1000 feet to the west of Azevedo Road and 0.85 miles south of SR 12 near Residence #18 (Figure 4). The hourly noise level data for the measurement period is presented in Figure 5. The Leq levels for the three full days of testing in the 24-hour periods beginning at midnight produced CNEL

11 values of 48 to 49 dBA. This range falls below these measured for other wind energy projects which had ranged from 56 to 74 CNEL. This is likely due to two different potential sources of noise. This location is setback from Azevedo Road which is larger than it has been in the previous long term Residence #18 noise measurements. This location is also somewhat protected from the prevailing wind by the local terrain. As a result, the trends in the L50 and LT1 L90 noise levels bear little resemblance to the wind speed measured at the nearby met tower at a height of 10m (Figure 6). This lack of correlation is further demonstrated with the data are Figure 4: Location of LT1 near cross-plotted where no consistent Residence # 18 increase in noise level is noted with increased wind speed (Figure 7). As

80 Leq L( 1) L(10) L(25) L(50) L(90)

40 Sound Pressure dBALevel, 35

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 :00 :0 :00 :0 :00 :00 :0 :00 :0 :0 :0 :00 :0 :00 :0 :0 :00 8:0 0:0 3 6:0 9 2:0 8 1 0 3:00 6 9:0 5:0 1:0 0 3:0 6 9:0 5:0 0:00 3 6:0 9 2:0 12 15 1 21 1 15 1 2 12 1 18 2 12:00 1 18:00 21 1 11/13 11/14 11/15 11/ 16 11/17 Time of Day Figure 5: Noise Levels measured at LT1 for November 13, 2009 through November 17 discussed in the appendices of previous reports8,9, this is atypical of sites that are more exposed to the prevailing winds. Figure 7 also indicates that the average L50 was measured to be about 40 dBA while the L90 background noise was about 1 to 2 dB less. These data also give some evidence of influence of SR 12 which may be the limiting factor in the daytime noise levels.

12 55 Wind Speed L(90) L(50) 50

5 Wind Speed,m/s& Sound PressureLevel. dBA 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 :0 :00 0 :00 0 :0 0 0 :0 :0 00 0 0 :0 00 :0 :00 :0 00 :0 8 1 0: 3 6: 9 1: 0:00 3 6:00 9 : 0: 3:00 6 9:00 : :0 0 3:00 6 9 : 12 15 :001 2 12: 0015: 18 :002 12 15: 0018 : 21 :00 12 15:0 018 21 :00 12:0 015 11/15 11/ 13 11 /14 Time of Day 11/16 11 /17

Figure 6: L50 and L 90 noise levels at LT1 plotted with wind speed data over the measurement period (10 minute intervals)

y = 0.16x + 39.32 60 R2 = 0.01

L(50) Sound Pressure Level, dBA Level, Pressure Sound L(50) 30

20 0 1 2 3 4 5 6 7 8 9 10 11 12 13 Wind Speed, m/s

Figure 7: L90 noise levels at LT1 plotted versus wind speed data over the measurement period (10 minute intervals) The second long-term measurement location at LT2 was located along Montezuma Hills Road about ¾ mile west of the intersection with Emigh Road and immediately west of Residence #20 (Figure 8). The noise data for LT2 are presented in Figure 9. At this location, the only option available at the time the measurements began was to secure the sound level meter to a utility pole very close to Montezuma Hills road. For this reason, the Leq levels used in the CNEL calculation are dominated by the intermittent vehicular noise on Birds Landing Road. This can be inferred from the L1 data (noise level

13 exceeded 1% of the time) which is often 30 to 40 dB greater than either L90, L50, or even L25 levels. This means there are quite short duration events occurring, but with high noise level. Given the general noise environment in the Birds Landing area and close proximity of the measurement location to the road, these are undoubtedly due to individual vehicle passbys which reach typically 80 to 85 dBA or more LT2 at this distance. Even though these events are of short duration, their Residence #20 levels are sufficiently high relative to the background levels that the energy average (Leq) level for the time Figure 8: Location of LT1 near period is governed by these isolated Residence # 20 events. As a result, the CNEL values, which range from about 58 to

85 Leq L( 1) L(10) L(25) L(50) L(90) 80

40 Sound Pressure dBALevel, 35

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 :00 :0 :00 :0 :00 :00 :0 :00 :0 :0 :0 :00 :0 :00 :0 :0 :00 8:0 0:0 3 6:0 9 2:0 8 1 0 3:00 6 9:0 5:0 1:0 0 3:0 6 9:0 5:0 0:00 3 6:0 9 2:0 12 15 1 21 1 15 1 2 12 1 18 2 12:00 1 18:00 21 1 11/13 11/14 11/15 11/ 16 11/17 Time of Day Figure 9: Noise Levels measured at LT2 for November 13, 2009 through November 17 63 dBA at this measurement location, are elevated due the close proximity of the microphone to the road. At farther distances from the road, the level of these events will be reduced. To obtain a noise level estimate at a distance representative of nearby Residence #18 which is offset from the road by approximately 50 ft, a 12 dB reduction can be assumed corresponding to two doublings of distances from the microphone location. The estimated CNEL values would then be in the range of 46 to 51 dBA. On November 16th, elevated background noise levels occurred between 3 and 6 am as

14 indicated by the L90 and L50 levels. On the morning of the following day, these higher levels did not occur although elevated levels did occur after 10 am. The cause could not be determined, however, they are not related to wind speed measured at the met tower in this region of the project (Figure 10). Similar to site LT1, LT2 displayed no correlation to wind speed, however, this was location also quite sheltered from the prevailing winds. In comparison to LT1, the L90 levels are lower on average by about 5 dB at LT2. This maybe due to decreased influence of SR 12 on the background noise levels at this

65 Wind Speed L(90) L(50) 60

Wind Speed, m/s & Sound Pressure Level. dBA Level. Pressure Sound m/s & Speed, Wind 5

0 0 0 0 0 0 0 0 0 0 0 0 0 0 :00 00 :00 :0 :0 00 :00 :0 :0 :0 :0 :00 00 :0 :0 1: 0:0 0 3 6: 00 9 5 8: 0 3:0 0 6 9:00 2 5:0 8:0 0 1:0 0:0 0 3 6: 00 9 5: 1:0 0:0 0 3 6:0 9 12 15:0018:002 12:001 1 21:00 1 1 1 2 12 1 18:0 2 12:0015:00 11/13 11 /14 11/ 15 11/16 11/ 17 Time of Day

Figure 10: L 50 and L90 noise levels at LT2 plotted with wind speed data over the measurement period (10 minute intervals) location which was both further away from the highway and more shielded by LT3 hills in that direction.

As was the case for LT2, the sound level meter at the third long-term measurement location was alongside Honker Bay Road on a utility pole just west of Residence #1 (Figure 11). This location was about ½ mile west of Olson Road and about 475 yards south of SR 12. Existing WTG’s were in the vicinity of this location, one line starting approximately ½ mile to the northwest, and another line Residence #1 approximately 0.8 miles to the southwest. The noise data at this site (Figure 12) only indicated the influence Figure 11: Location of LT3 near of local traffic events on Honker Bay Residence # 1 Road (similar to LT2) during a few

15 85 Leq L( 1) L(10) L(25) L(50) L(90) 80

40 Sound Pressure Level, dBA Level, Pressure Sound 35

0 0 0 0 0 0 0 0 0 0 0 0 0 0 00 0 :00 00 0 0 :00 00 :0 :0 :0 :00 00 0 :0 :0 : : 0: 3:00 6 9:00 : 0:00 3: 6:00 9 : 0 3:00 6 9:00 5 : 0: 3 6:00 9 15 18 21 :00 12:0 15 18: 0021 : 12 :0015:0 18 21: 00 12 1 18:0 21 12: 00 11/13 11/14 11/15 11/16 11/ 17 Time of Day

Figure 12: Noise Levels measured at LT2 for November 13, 2009 through November 17 time intervals during the measurement period. For a majority of the time, the range of the L90 and through L1 levels was relatively small, 10 dB or less, and L90 were considerably higher than either LT1 or LT2 indicating more constant noise at LT3. The CNEL values calculated from the hourly Leq levels and ranged from 66 to 68 dBA falling more in the range of values measured previously in the Montezuma Hills region. However, from the cross-plot of L90 noise level versus wind speed (Figure 13), there appears to be virtually no correlation with wind speed (i.e. R2=0.07) although there is an upward trend with

y = 1.07x + 44.21 2 70 R = 0.07

L(90) Sound Pressure Level, dBA Level, Pressure Sound L(90) 30

20 0 1 2 3 4 5 6 7 8 9 10 11 12 13 Wind Speed, m/s

Figure 13: L90 noise levels at LT3 plotted versus wind speed data over the measurement period (10 minute intervals)

16 increased wind speed. At this location, potential sources of the background noise include traffic on SR 12, construction on SR 12, existing WTGs, and wind-induced background noise as this site is less protected from prevailing wind than the other two locations.

NOISE ASSESSMENT

The noise assessment consists of four elements. The first is a review of the noise performance of the wind turbine generators currently being considered for the project. The next element is the estimation of noise levels based on the proposed site plans. The third element is the assessment of the predicted levels relative to the appropriate regulations and guidelines. Finally, different mitigation strategies are discussed.

Wind Turbine Noise Performance

At this time, the Shiloh III Wind Project is considering the use of one of three different wind turbine generators. These are the Vestas V90 2.0 MW, the REpower MM92 2.0 MW, or the Liberty 2.5 MW. All three wind turbine generator designs are of an upwind configuration avoiding some of the low frequency concern regarding older, downwind turbines. The acoustic performance data available from the three potential suppliers is somewhat different. For the Vestas and REpower units, overall A-weighted sound power levels are available in 1 m/s increments from 4 to 9 m/s. Typical of many WTGs of this size, operation begins once the wind speed reaches 4 m/s while at speeds of 8 m/s or greater, the sound power level remains almost constant with speed. The overall levels for these units as a function of speed are presented in Figure 14. For the Liberty WTG, the

108 Vestas V90 2.0 MW 107 Repower MM92 2.0 MW 106 Liberty 2.5 MW 105 104 103 102 101 100 99 98 Sound Power Level (dBA) Level Power Sound 97 96 95 94 012345678910111213141516 Wind Speed, m/s Figure 14: Overall A-weighted sound power levels for the Vestas, REpower, and Liberty WTGs as a function of wind speed sound power level is only reported at the International Standard IEC 61400-1110 procedure test speed of 8 m/s. In order to estimate sound levels for the Liberty WTG as function of wind speed, a speed profile similar to that of the REpower WTG is assumed

17 level shifted 1 dB higher as reflected by the difference in level provided at 8 m/s (Figure 14). For the REpower WTG, octave band sound power levels are available at the reference speed of 8 m/s and are shown in Figure 15. For the Vestas WTG, octave band

110 Vestas V90 2.0 MW

105 Repower MM92 2.0 MW Liberty 2.5 MW

100

85 Sound Power Level (dBA)

75 31.5 63 125 250 500 1000 2000 4000 8000 Octave Band Center Frequency, Hz

Figure 15: A-weighted Octave band sound power levels for the Vestas, REpower, and Liberty WTGs at a wind speed of 8 m/s spectra were estimated from data available for the V90 3.0 MW unit offset by the difference in overall A-weighted sound power level at 8 m/s for the two WTGs. For the Liberty WTG, the spectra were estimated by offsetting that of the REpower by 1 dB. In assessing the noise produced by the project, the octave band data are used to determine propagation losses due to atmospheric attenuation and overall C-weighted levels for comparison to the County requirements. The sound power level as a function of wind speed is used to calculate predicted CNEL values as determined from actual wind speed distributions measured in the Birds Landing area and to evaluate the audibility of the WTG noise relative to wind induced background noise. The tonality of the three units under consideration is not known, however, most modern WTGs of this type do not produce prominent tones under normal operation.

Using the spectral data of Figure 15, the overall C-weighted sound power levels at 8 m/s were calculated to be 114.4 dBC for the Vestas unit, 114.5 dBC for the REpower, and 115.5 dBC for the Liberty. These levels are about 10 dB greater than the corresponding A-weighted level at 8 m/s shown in Figure 14. Typically a difference of 20 dB or more between the A & C-weighted is the threshold of concern for low frequency noise relative to A-weighted levels7. Low frequency noise from any of the turbines will be well below any of the regulations or guidelines if the A-weighted sound levels are achieved.

Steady Noise Level Estimation

As sound spreads out from a noise source, the underlying physics of sound propagation determines that the sound will reduce by 6 dB for each doubling of distance away from

18 the source. In addition to this expected attenuation, other phenomena can create even more excess attenuation. Given the long propagation distances between some of the wind turbine generators and residences, the effects of excess sound attenuation due to atmospheric absorption were incorporated into the calculated levels based on the measured and assumed octave band spectra of Figure 15. Some amount of this absorption is present at all times although it will vary somewhat with temperature and humidity. For a region like Montezuma Hills with rolling hills and grassland, significant excess attenuation can also be created by the barrier effect in between a wind turbine generator and a receptor and by sound propagation over the acoustically soft ground. On the other hand, this excess attenuation can also be reduced by temperature gradients and/or wind speed gradients. These latter two effects are not constant with time and can only be estimated with detailed data. As a result, the excess attenuation at any location and time can vary from none to some large amount. For estimating the noise levels resulting from the wind turbine generators in the Montezuma Hills, it was assumed that the excess attenuation was zero. For downwind noise receptors, this assumption is reasonable in that when the wind is blowing, the wind will diffract the sound downward defeating any positive effect of excess attenuation by shielding of the hills and reflection from the soft ground. For upwind receptors, the wind will diffract sound upwards creating more excess attenuation. Thus, a very conservative approach is to assume no excess attenuation and just consider 6 dB per doubling of distance away from the noise source as the only attenuation beyond atmospheric absorption. To account for some reflection from ground, it was assumed that 70% of the sound striking the ground was reflected. This is also a very conservative assumption for grassland and plowed fields. Under these assumptions, the resultant estimations define the highest potential noise levels and are greater than what would be expected most of the time. Implied in the analysis of the wind turbine generator noise is the assumption that turbines radiate sound uniformly in all directions. Data from other, similar size wind turbine generators in use in the Birds Landing area suggests this is a reasonable assumption, as does the IEC Standard8 for sound power determination. Using this assumption along with the 70% ground reflection, the steady sound pressure level 1000 feet from a single wind turbine generator operating at the reference wind speed of 8 m/s is calculated to be 44.2 dBA for the Vestas WTG, 45.2 dBA for the REpower, and 46.2 dBA for the Liberty.

The first step to assessing the noise impact of the Shiloh III Wind Project on residential receptors in and around the project was to calculate the steady noise levels based on the maximum sound power at 8 m/s for comparison to the 44 dBA criterion. This was done using the site plans shown in Figure 2 and 3. Residences #4 through #6, #10, #12 through #15, #17 and #21 were dropped from impact consideration as they were all at least 0.6 miles away from the closest WTG and could not possibly approach the 44 dBA steady noise level criteria. For the remaining residences, the sound pressure level from each individual, adjacent wind turbine generator was calculated for each specific residence. The total noise level was then calculated by summing the contribution of the individual turbines until the turbines were too distant (more than 4000 ft) to add more to the total sound level. The results of these calculations are presented in Figure 16 for steady A-weighted noise levels long with the 44 dBA continuous criterion derived from the Solano County Standard. For eight of the residences (#1-3, #11, #13, and #18-20), the levels exceed the 44 dBA criterion for all three of the WTGs under consideration. For Residence #9, the criteria is only exceeded for the Liberty WTG and then only by 0.5 dB. To evaluate the low frequency concerns, the C-weighted levels at each residence

60 Vestas V 90 2.0 MW REpower MM92 2.0 MW 55 44 dBA Continuous Liberty 2.5 MW Level Criterion

Overall Sound Pressure Level, dBA Level, Pressure Sound Overall 35

30 1 2 3 7 8 9 11 13 16 18 19 20 Residence Number Figure 16: Calculated steady overall A-weighted noise levels for all residences approaching or exceeding the 44 dBA criteria were estimated in the same manner as was done for the A-weighted levels. These are presented in Figure 17 along with the 64 dBC equivalent continuous criterion. In this case, all of the residences for all three WTG options are below the criterion.

70 Vestas V 90 2.0 MW 64 dBC Continuous REpower MM92 2.0 MW Level Criterion Liberty 2.5 MW 65

Overall Sound Pressure Level, dBC Level, Sound Pressure Overall 45

40 1 2 3 7 8 9 11 13 16 18 19 20 Residence Number

Figure 17: Calculated steady overall C-weighted noise levels for all residences approaching or exceeding the 64 dBC criteria

20 CNEL Estimation

The above analysis determines the highest possible steady noise levels based on operation at wind speeds producing the maximum sound power output. From Figure 14, it is seen that sound power for the various WTGs does vary considerably with wind speed below 8 m/s. In addition, the wind speed itself varies considerably over a 24-hour period and from day to day. Another means to assess the noise impact of the Shiloh III Wind Project is to provide a more explicit estimation of the expected CNEL and compare it to the 50 dBA criterion. To refine the calculation of CNEL actual, yearly average wind speed distributions can be used instead of the assumed 85% average operational scenario. For the Birds Landing area, the yearly distribution of the wind speed for the hours corresponding to the daytime, evening, and nighttime hours used to determine CNEL are shown in Table 3. This distribution can be used to determine the percentage of time within each CNEL period that each of the three wind speed groupings occur as shown in Table 4. For the 0 to 3.9 m/sec bracket, the wind turbine generators would not be

Table 3: Yearly average wind speed distributions for the Montezuma Hills area expressed in CNEL day, evening, and night time periods

Time Period Wind Speed (m/s) 7 am - 7 pm 7 pm - 10 pm 10 pm - 7 am 24 hour total 0-3.9 10.0% 1.7% 4.5% 16.2% 4-7.9 17.7% 2.8% 9.2% 29.6% 8-25 22.3% 8.0% 23.9% 54.2% Percent of 24 hours 50.0% 12.5% 37.5% 100.0%

Table 4: Yearly average wind speed distributions for the Montezuma Hills area within each CNEL time period

Time Period Wind Speed (m/s) 7 am - 7 pm 7 pm - 10 pm 10 pm - 7 am 0-3.9 20.0% 13.6% 11.9% 4-7.9 35.3% 22.4% 24.4% 8-25 44.7% 64.0% 63.7% total 100.0% 100.0% 100.0% operating and, hence, would produce no noise. For the other two speed brackets, the generators would be operating and the sound power source levels as a function of wind speed can be used to estimate an acoustic mean noise level in each bracket. For this purpose, sound power level versus wind speed data for each of the three WTGs are used (Figure 14). The mean level is determined as the acoustic energy average over the speed bracket. The results of this calculation are given in Table 5.

As an example of this approach, the continuous level for a wind speed of 8 m/sec is 46.2 dBA for Residence #1. The noise levels corresponding to the 0 to 3.9 m/sec, 4 to 7.9 m/sec, and 8 to 25 m/sec wind speed brackets are then 0, 43.0, and 46.2 dBA, respectively. Using the wind speed percentages in the Tables 3 and 4, the equivalent Leq for each CNEL time period can be determined by performing an energy average for the

21 Table 5: Sound power levels for the acoustic mean energy within each wind speed bracket for each WTG under consideration

Mean Overall Sound Power Level, dBA Wind Speed (m/s) Vestas REpower Liberty 0-3.9 0.0 0.0 0.0 4-7.9 101.9 101.8 102.8 8-25 104.0 105.0 106.0 period weighted by the fractional distribution. After this is done for each time period, the CNEL can be determined through the normal calculation process. For Residence #1 and the REpower WTG, this yields a CNEL value of 51.6 dBA. The CNEL values for each residence and each WTG option are presented in Figure 18 along with the 50 CNEL

65 Vestas V 90 2.0 MW

REpower MM92 2.0 MW CNEL 50 60 Liberty 2.5 MW Criterion

Overall Sound Pressure Level, dBA Level, Sound Pressure Overall 40

35 123789111316181920 Residence Number Figure 18: CNEL values calculated using annual average wind speed data and WTG sound power level as a function of wind speed criterion level. For the CNEL values determined by this method, only Residences #1, #2, #13, and #18-20 exceed the criterion for all three WTGs. For Residences #3 and #11, the 50 CNEL limit is exceeded for both REpower and Liberty WTGs. In comparing Figures 18 and 16, it will be noted that there is a constant offset between the steady noise levels and the CNEL value from residence to residence for each WTG type. Applying this offset relative to 50 dBA CNEL yields equivalent steady levels of 44.4 dBA for the Vestas WTG, and 44.6 dBA for the REpower and Liberty. These slight differences are due to small differences in sound power level versus wind speed profiles (Figure 14). Another way of stating this is that if the predicted steady level at a residence is 44.4 dBA or less for Vestas WTG, then the 50 dBA CNEL criteria will be met based on the average wind speed distributions. Similarly, if the REpower and Liberty are 44.6 dB or lower at given residence, the 50 dBA criteria will be meet for those WTGs.

In previous analysis of the noise produced by wind energy projects in the Montezum Hills area8,9, the CNEL from wind induced background noise has been estimated based

22 the above distribution of wind speed for more open areas. As noted in the LT1 and LT2 data discussion, for some residences in the Shiloh III project this may not be applicable due to sheltering from the winds measured on nearby met towers. For the open cases, the wind induced background noise has been estimated from the linear relationship between L50 and wind speed as shown in Figure 16. Using these data and the same process as was done for wind turbine generators, a CNEL of 55.9 dBA was calculated for the wind induced, background noise based on the yearly average wind data.

Lower Frequency and Infrasonic Considerations

Lower frequency and infrasonic noise generation levels are typically not available from the wind turbine supplers. In the absence of such data for WTGs under consideration, data from an existing Vestas V80 1.8 MW in the Birds Landing area was evaluated for lower frequency and infrasonic noise. The measured octave band spectra for the V80 unit are compared to the three candidates for the Shiloh III Project in Figure 19 and are shown to be similar to the others in the range for 63 to 1000 Hz. As a result, data for the Vestas V80 1.8 MW was assumed to be representative of the other WTGs down to lower frequencies and was considered in more detail.

110 Vestas V90 2.0 MW Repower MM92 2.0 MW 105 Liberty 2.5 MW Vestas V80 1.8 MW

100

85 Sound Power Level (dBA)

75 31.5 63 125 250 500 1000 2000 4000 8000 Octave Band Center Frequency, Hz

Figure 19: Measured A-weighted Octave band sound power levels for an installed Vestas V80 1.8 MW unit compared to reported levels for the Vestas V90 2.0 MW, REpower, and Liberty WTGs at 8 m/s

The Vestas V80 1.8 MW unit was measured as part of the High Winds wind energy project in May, 2003. One-third octave band noise levels from 2 to 200 Hz are shown in Figure 20 with the WTG operating and not operating for a wind speed of 7.2 m/s for sound pressure levels projected to 1000 ft using the sound propagation model described previously. At this distance, the WTG produces a steady A-weighted level of 44.8 dB. Also displayed in this plot are the criteria the used by Kern County and disturbance threshold used in the UK. Relative the Kern County criteria, the measured level are 9 to 15 dB lower with the biggest difference occurring at the lowest frequencies. Relative to

85 Operating 80 Not Operating 75 Kern Co Limits UK Disturbance 70

50 Sound Pressure Level, dB Level, Pressure Sound 45

2 4 5 8 0 5 5 2.5 .15 6.3 1 16 20 2 40 50 63 80 60 3 12.5 31.5 100 12 1 200 1/3 Octave Band Center Frequency, Hz Figure 20: Measured one-third octave band noise levels for a WTG operating and not operating as installed in Montezuma Hill wind energy project similar in sound power level to those WTGs considered for Shiloh III the UK threshold, the measured levels are well below the criteria at the lowest frequencies (2 to 40 Hz) while from 50 to 125 Hz, they below or equal to the threshold. From 4 to 40 Hz, the measured levels are also below the audibility threshold7. Figure 20 also indicates that the difference between the WTG operating and not operating at a wind speed of 7.2 m/s. Below 50 Hz, whether the WTG is operating or not has no effect on the measured noise levels.

Assessment of Estimated Noise Levels

The criteria for assessing noise impact in Solano County come from both the Solano County General Plan and the zoning regulations of the Solano County Code. In the Public Health and Safety Chapter, Leq limits of 55 dBA and 50 dBA are set in outdoor residential spaces for day and nighttime, respectively. Lmax limits are also established, however, given the steady noise levels produced by WTGs throughout their upper operating range, these are not approached if the Leq requirements are met. Since WTGs operate in both the day and nighttime, the nighttime limit of 50 dBA is appropriate for comparing the predicted, steady noise levels (Figure 16). Although argumentative, if it is assumed that the noise produced by the WTGs is a “recurring impulsive sound”, the nighttime limit would be lowered to 45 dBA for the immediate vicinity of the residences.

In the Resources Chapter of the Solano County as well as the zoning regulation of the Solano County Code, the requirement is that CNEL 50 contour of the wind energy project not extend to residential areas or to individual residential structures. Applying this criterion to the resultant predicted noise levels given in Figure 18, there are a number of combinations of WTG options and residences that exceed this requirement. The cases where one or more combination is above 50 dBA CNEL are summarized in Table 6 with

24 difference in level for the prediction and criterion. As noted previously, these range from ½ to 5 dB. In regard to lower frequency noise, from Figure 17 it is seen that the predicted C-weighted levels are 6 dB below the 64 dBC limit used by Alameda County indicating no lower frequency impact based on that criterion. In regard to the Kern County limits, based on the results of an existing WTG noise at lower frequency, the estimated levels for the Shiloh III project will be at least 5 dB below these requirements if the overall A-weighted level is maintained to be 44.7 dBA or lower. That is, the levels shown in Figure 20 correspond to a steady level of 44.7 dBA and hence if the steady level were even 49.7 dBA, the low frequency requirement would still be met. In regard to the UK disturbance threshold, these levels would also be met at all frequencies if the overall A-weighted level is at or below 44.7 dBA. Thus any mitigation applied to achieve the A- weighted requirements will also assure that any low frequency criteria are also met.

In addition to the Solano County regulations, the appropriate CEQA criteria should also be considered. The first of these is whether or not the predicted levels exceed the local regulations. From Table 6, it is seen that this occurs for as many as eight residences in the project area. The second criterion is whether project noise levels will produce a

Table 6: Amount of noise reduction (in dB) required to achieve the 50 dBA CNEL limit for each residence in excess of the limit

Residence # Wind Turbine Generator 1 2 3 1113181920 Vestas V 90 2.0 MW 0.8 2.9 0.4 2.5 2.6 3.2 REpower MM92 2.0 MW 1.6 4.0 0.8 0.6 1.2 3.3 3.4 4.0 Liberty 2.5 MW 2.6 4.7 1.8 1.6 2.2 4.3 4.4 5.0 substantial permanent increase in ambient noise levels. For those locations where the existing CNEL values are above 50 dBA, the increase in noise level will be less than 3 dB if the noise is mitigated to the level in the county zoning requirement. For areas below 50 dBA, the impact would not be significant unless the existing levels were below 45 dBA thus producing a 5 dB or more increase in level. From the long-term noise acquired in this study and the analysis of wind-induced background noise in locations susceptible the prevailing wind conditions, none of the existing levels are known to be below a CNEL of 45 dBA. As a result, no significant CEQA noise impact would be expected for wind turbines for any of the project options under this criterion as long as the zoning regulation requirement is met.

In regard to low frequency and infrasonic noise, the levels expected from the Shiloh III project are expected to be well above any of the available criteria. Based on the results of Figure 20 and the ensuing discussion, the wind turbines do not exhibit any potential to generate high levels of infrasonic noise either at the residences in the direct vicinity of the project or at greater distances.

Mitigation Alternatives

From the above analysis, the primary objective of mitigation strategies is reduce the values in Table 3 to 0 dB or less, that is, for the predicted CNEL levels to be 50 dBA or

25 less. To achieve the noise reductions, mitigation falls into the categories of: 1.) reducing the noise of the source (WTG’s); 2.) modifying the path between the source and receiver; 3.) modifying the receiver.

Mitigation through measures applied to the source in this project would mean either using WTG’s producing less noise or limiting the operation of some WTG’s on a 24 hourly basis. Of the WTGs under consideration for the Shiloh III project, selecting the Vestas unit would have the most positive effect on reducing the source levels and the predicted noise levels at the residences. The 2 dB lower levels for this WTG would mean that only 6 residences would have CNEL levels over 50 dBA. As a result, fewer other mitigation measures would be required. Another alternative to address the source levels would be to pursue options with the WTG suppliers that produce to lower noise levels. Some of these suppliers do offer such configurations; however, these may result in reduced electrical power output. Such options may have an ongoing impact on the total power produced by the wind energy project or require the use of additional WTGs. Theoretically, a third source level alternative may be limiting operating time individual WTGs such that the noise level meet a 50 CNEL limit for any 24 hour period. Because of the nighttime penalty, this would most likely mean curtailing operation in the nighttime hours based on the number of hours of operation during the daytime. However, determining when and for how long operation should be curtailed would be very problematic, particularly with respect to not loosing electrical power arbitrarily.

Mitigation by altering the path between the WTG’s and residences may be more feasible in terms of not decreasing electrical power output. Path mitigation is typically achieved by inserting barriers or by increasing distance. Lowering levels by placing barriers between the source and the receiver, however, would not be effective in this case because of the height of the WTG’s, the hilly terrain, and the potential for the prevailing wind to negate any barrier effectiveness through sound diffraction effects. The second path related mitigation method is increasing the distance between the WTG sources and the residential receivers. For a single WTG, increasing the separation between it and a receiver by a factor of two would reduce the received sound level by 6 dB. However, when multiple receivers are in vicinity of the residence, relocating more than one or two WTGs may be necessary to affect reductions of even a couple of dB. To reduce the accumulated level, relocating those WTGs closest to any given residence will provide the biggest reduction with least amount of disruption of the site plan. Because the relocation scenarios are virtually limitless and the fact that one WTG may have a significant, but differing amount of contribution to more than one residence, optimizing the siting for noise can be a somewhat iterative process.

In order to illustrate how the plan may be optimizing for Shiloh III as well as identify the most significant contributors to the noise at the residences exceeding 50 dBA CNEL, scenarios for each residence and each of the three WTGs under consideration were developed. This was done in an iterative process also. It was attempted to relocate WTGs to an unspecified location 3000 ft away. If the 50 dBA criterion was not achieved with a smaller number of relocations, then 4000 ft was used, and finally 5000 ft. The larger distances are necessary when the limit can not be achieved because the number WTGs in the range of 3000 ft are too great to all be feasibly relocated. The results of this analysis are provided in Table 7. As would be expected from the relative difference in sound power production and the results shown in Figure 18, use of the Liberty WTG

26 would require the most relocations while the Vestas unit would be the least. For residences through #13, the number of affected WTGs is fairly well contained. For the last three, Residences #18 through #20, numerous relocations are needed to achieve 50 dBA. In these cases, the residences are surrounded by more than 180º with a number of WTGs at closer distances.

Table 7: Wind turbine generators that could be considered for relocation to achieve the 50 dBA CNEL limit for each residence in excess of the limit

Wind Turbines Required to Be Moved to meet 50 CNEL Residence # Vestas REpower Liberty 1 A12 or A13 A12 or A13 A12 and A13 2 B18 and B19 B18, B19, and B20 B18, B19, and B20 3 B18 or B19 B18 and B19 11 C25 C25 and C33 13 C43 C43 C41* and C43* 18 C37*-C39* and C42* C37*-C39*, C42* and C37**-C44** C44* 19 F5*, F6*, F8*, E10*, and F5*, F6*, F8*, E10*, F5**- F8**, E10**, E11**, E11* E11*, C40*, E6*, and E8* C40**, E6**, and E8**

20 E13-E16 and E21-E23 E13*-E16*, E21*, and E13**-E16** and E21**- E23* E23** * 4000 ft away **5000 ft away

The third method of mitigation is addressing of the receiver. One approach to this is the consideration of the interior noise levels due to the project inside the residential structures. It should be noted that only exterior noise requirements are specified in the Solano County Zoning Regulations for wind energy projects. In the Solano County General Plan, the Health and Safety Element sets 35 dBA as the maximum allowable interior noise level for interior residential spaces with the windows and doors closed. From Figure 16, the continuous, steady-stats exterior levels for all residences and WTGs are 50 dBA or less. Achieving a corresponding interior continuous level of 35 dBA would require an exterior to interior noise reduction of at least 15 dB. Based on previous residential noise reduction measurements made in the Birds Landing area on both newer and older structures, such reduction is likely. The newer structures with better sealed windows were found to produce noise reductions of about 22 to 26 dB with the windows closed based on a typical WTG noise spectrum. For older structures, the noise reductions ranged from 19 to 26 dB depending on the amount of glass area and whether the windows had been replaced at some time. Based on these data, the residences affected by the Shiloh III WTGs would more than achieve the 35 dBA standard.

In the Solano County Zoning Regulations for wind energy projects, a second approach to addressing the received noise levels from the Shiloh III project is allowed. This is to obtain noise waivers from the property owners consenting to the construction of one or more turbines that would produce exterior noise levels at their residence exceeding the

27 County limits once the WTGs become operational. To implement this approach, prior to beginning of construction for turbines locations that would result in levels exceeding the 50 dBA CNEL or 44 dBA steady noise level criteria at residences nos. 1, 2, 3, 11, 13, 18, 19, and 20, Shiloh III shall provide the County with written waivers from the property owners.

Under this latter approach of receiver based mitigation, there is also less sensitivity to changes in the WTG site plan unless new specific residences are identified as being above the criteria. In a site plan revision that occurred after the above analysis, the number of WTGs was reduced from 65 to 59 WTGs with some units actually being closer to some of the already impacted residences in the eastern portion of the plan. The western portion of the plan remained unchanged. Under this revision, the estimated noise levels increased for a total of five residences all of which were identified as exceeding the criteria under the previous plan. The affected residences and increase in level are shown in Table 8. Corresponding to Figure 16 of for the original site plan, the sound levels at

Table 8: Increase in noise level (dB) produced by latest WTG site plan revision

Residence # 11 13 18 19 20 1.7 0.7 2.1 4.5 0.8 the residences exceeding the 44 dBA steady criterion and affected by the 59 WTG site plan are shown in Figure 21 along with the criterion. The noise reductions required at

65 Vestas V 90 2.0 MW 44 dBA Continuous Level Criterion 60 REpower MM92 2.0 MW Liberty 2.5 MW

Overall Sound Pressure Level, dBA Level, Pressure Sound Overall 35

30 11 13 18 19 20 Residence Number

Figure 21: Calculated steady overall A-weighted noise levels for residences affected by the 59 WTG unit site plan and approaching or exceeding the 44 dBA criteria

28 each of these same residences necessary to achieve the CNEL 50 criterion are presented in Table 9 which is analogous to results shown in Table 6 for the original site plan. Mitigation by use of noise waivers remains unchanged from that identified for the previous site plan.

Table 9: Amount of noise reduction (in dB) required to achieve the 50 dBA CNEL limit for each residence affected by the 59 WTG unit site plan

Residence # Wind Turbine Generator 11 13 18 19 20 Vestas V 90 2.0 MW 1.7 1.1 4.6 7.1 4.0 REpower MM92 2.0 MW 2.3 1.9 5.4 7.9 4.8 Liberty 2.5 MW 3.3 2.9 6.4 8.9 5.8

REFERENCES

1 Information on Levels of Environmental Noise Requisite to Protect Public Health and Welfare with an Adequate Margin of Safety, U.S. Environmental Protection Agency, Washington, D.C., March 1974, p. 29. 2 Guidelines for Preparation and Content of Noise Elements in General Plans, California Department of Health Services, Office of Noise Control, 1976. 3 Health and Safety Element – Seismic Safety, Safety, Noise, Solano County General Plan, County of Solano, May, 1977. 4 Zoning Regulations, the Code of Solano County, Solano County Department of Environmental Management, Chapter 28 5 Standard Conditions of Approval for Wind Farm Permits, Item 16, Alameda County, May 1998. 6 Development Standards and Conditions, Section 19.64.140, Chapter 19.64 Wind Energy (WE) Combining District, Title 19 Zoning, the Ordinance Code of Kern County, California, June 15, 2006. 7 R. O’Neal, R. Hellweg, and R. Lampeter, “A Study of Low Frequency Noise and Infrasound from Wind Turbines”, prepared by Epsilson Associates, Inc. for NextEra Energy Resources, LLC, 700 Universe Blvd., Juno Beach, FL, Report No. 2433-01, July 2009. 8 Shiloh II Wind Plant Project Final and Draft Environmental Impact Reports, Noise Technical Report available at: http://www.co.solano.ca.us/resources/ResourceManagement/11%20Appendix%20F.pdf 9 Montezuma Wind Project Draft & Final Environmental Impact, Noise Technical Report available at: http://www.co.solano.ca.us/resources/ResourceManagement/Montezuma/Volume%20II %20-%20Appendices/08%20-%20Appendix%20F%20-%20Noise.pdf. 10 International Electrotechnical Commission, “Wind Turbine Generator Systems- Part 11: Acoustic Noise Measurement Techniques”, IEC 61400-11, IEC, Geneva Switzerland, 2002.

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Appendix F Engineering Report Concerning the Effect of Microwaves Upon Nearby FCC Licensed Facilities

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ENGINEERING REPORT CONCERNING THE EFFECT UPON NEARBY FCC LICENSED RF FACILITIES DUE TO THE CONSTRUCTION OF A WIND TURBINE FARM In SOLANO COUNTY, CALIFORNIA “SHILOH III”

enXco Development Corp.

December 9, 2009

By: B. Benjamin Evans, P.E. Evans Associates 210 South Main Street Thiensville, WI 53092 262-242-6000 PHONE 262-242-6045 FAX www.evansassoc.com

Shiloh III Wind Project

ENGINEERING REPORT CONCERNING THE EFFECT UPON NEARBY FCC LICENSED RF FACILITIES DUE TO THE CONSTRUCTION OF SHILOH III WIND TURBINE FARM In SOLANO COUNTY, CALIFORNIA

enXco Development Corp.

I. INTRODUCTION

This engineering report describes the results of a study and analysis to determine the locations of federally-licensed (FCC) microwave and fixed station radio frequency facilities that may be adversely impacted as a result of the construction of enXco wind turbines in the Shiloh III project area in Solano County, California. This document describes impact zones and any necessary mitigation procedures, along with recommendations concerning individual wind turbine siting. All illustrations, calculations and conclusions contained in this document are subject to on-site verification1.

Frequently, wind turbines located on land parcels near RF facilities can cause one or more modes of RF impact, and an iterative procedure may be required to minimize adverse effects. This procedure will ensure that disruption of RF facilities either does not occur or, in the alternative, that mitigation procedures will be effective. The purpose of this study is to facilitate the siting of turbines to avoid unacceptable impact to FCC licensed RF facilities.

The wind turbines proposed will be up to 124.7 meters above ground level to the tip of one blade at the 12:00 position. The wind turbine farm occupies a land parcel near the intersection of State Highways 12 and 113, about 15 miles southeast of Fairfield, California.

Using industry standard procedures and FCC databases, a search was conducted to determine the presence of any existing microwave paths crossing the subject property, as well as other RF facilities within or adjacent to the identified area. enXco plans to construct 65 turbines on the Shiloh III area. The project area and turbine layout are shown on Figure 1.

1 The databases used in creating the attached tables and maps are generally accurate, but anomalies have been known to occur. An on-site verification survey is suggested as part of the due diligence process.

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Figure 1 - Shiloh III Property and Turbine Locations with Microwave Paths

The FCC database search revealed 66 microwave links that traverse the search area indicated by the red outline in Figure 1. In addition, several land mobile base stations and broadcast stations within and near the property have been identified. The locations of these microwave paths and fixed station facilities are shown in the detailed maps of the figures below.

The attached profiles and maps were generated based upon the operating parameters of the FCC- licensed stations as contained in the FCC station database.

The following analysis examines the pertinent FCC licensed services in the area for impact. This analysis assumes that all licensed services have been designed and constructed according to FCC requirements and good engineering practice. If this is not the case, the impacted facility must share responsibility with the wind turbine developer for the costs of any mitigation measures2.

2 For instance, some microwave paths may have insufficient ground clearances as they are presently configured.

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Figure 2 below shows the RF facility detail for the western portion of the proposed site (active sites only):

Figure 2 - Western Detail (Active Facilities Only)

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Figure 3 below shows the RF facility detail for the central portion of the proposed site (active sites only):

Figure 3 - Central Detail (Active Facilities Only)

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Figure 4 below shows the RF facility detail for the eastern portion of the proposed site (active sites only):

Figure 4 - Eastern Detail (Active Facilities Only)

II. ANALYSIS OF MICROWAVE LINKS

An extensive analysis was undertaken to determine the likely effect of the new wind turbine farm upon the existing microwave paths, consisting of a Fresnel x/y axis study and a z-axis (height) evaluation. The microwave path is overlaid on the USGS topographic base maps attached, and is also available as overlays for the GeoPlanner™ program files.

Important Note: Microwave path studies are based upon third party and FCC databases that normally exhibit a high degree of accuracy and reliability. Although Evans performs due diligence to ensure that all existing microwave facilities are represented, we cannot be responsible for database errors that may lead to incomplete results. However, should such situations occur, Evans would perform an engineering analysis at no additional cost to determine

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how any additional or modified facilities can be accommodated or, if wind turbine structures are already built, determine a method to re-direct the offending beam path. It is recommended that a consultant visit the site to visually check for anomalies.

For this microwave study, Worst Case Fresnel Zones (WCFZ) were calculated for each microwave path (see Figure 1, Table 1). The mid-point of a microwave path is the location where the widest (or worst case) Fresnel zone occurs. Possible geographic coordinate errors must be added to the Fresnel zone clearance numbers3. The radius R of the Worst Case Fresnel Zone, in meters, is calculated for each path using the following formula:

where D is the microwave path length in kilometers and FGHz is the frequency in gigahertz.

In general, the WCFZ is defined by the cylindrical area whose axis is the direct line between the microwave link endpoints and whose radius is R as calculated above. This is the zone where the siting of obstructions should be avoided.

Evans Associates has identified 13 active microwave paths that could potentially be impacted by turbines in the project area. These are tabulated below in Table 1:

Lat Site Long Site Lat Site Long Site Xmit Rcv Ele WCFZ Nearby ID Call 1 1 2 2 Ele m m (m) Turbines* 2 KMT32 38.39547 122.1 38.15936 121.7058 831.5 38.7 21.96 3 KMT49 38.39406 122.0988 38.17028 121.81 829.1 50.3 52.71 B16,B17,B18 8 WLL763 38.02989 122.0023 38.15973 121.7061 195.7 56.1 14.45 E13,E14 C24,C26, C27, 9 WLR685 38.15964 121.7061 38.18908 121.8152 56.1 88.4 8.45 C35, C37, F6 10 WLR685 38.15964 121.7061 37.93936 121.488 62.2 37.1 14.83 11 WLR685 38.15964 121.7061 38.02989 122.0023 56.1 195.7 14.50 E13,E14 12 WLS839 38.40878 122.1105 38.15659 121.6916 883 22.2 60.46 14 WLU612 38.29897 121.9991 38.16514 121.7266 285 51.2 14.11 15 WMN679 38.16514 121.7268 38.29897 121.9991 51.2 285 14.06 16 WNEO800 38.09297 121.8855 37.9427 121.8852 18.2 589.8 10.83 17 WNEO802 37.9427 121.8852 38.09297 121.8855 589.8 18.2 10.87 C24,C26, C27, 18 WPJE264 38.18908 121.8152 38.15964 121.7061 88.4 56.1 8.42 C35, C37, F6 19 WPJE265 37.93936 121.488 38.15936 121.7058 37.1 62.5 14.78 C24,C26, C27, 20 WPOT974 38.15945 121.7061 38.18908 121.8153 48.1 91.4 6.23 C35, C37, F6 C24,C26, C27, 21 WPOT975 38.18908 121.8153 38.15945 121.7061 91.4 48.1 6.50 C35, C37, F6 22 WPTP325 38.15936 121.7058 38.39547 122.1 38.7 831.5 22.25 23 WQFQ892 38.17028 121.81 38.39406 122.0988 50.3 829.1 52.61 B16,B17,B18

3 Many microwave facilities were built before accurate methods were available to establish exact geographic coordinates (such as GPS). It is not unusual for database errors of up to 4 or 5 seconds to occur, which can effect the positioning of critical turbines located near Fresnel paths.

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Lat Site Long Site Lat Site Long Site Xmit Rcv Ele WCFZ Nearby ID Call 1 1 2 2 Ele m m (m) Turbines* 24 WQJL310 38.17122 121.8461 38.12577 121.8346 68.2 120.7 5.88 25 WQJL311 38.02125 121.9878 38.12577 121.8346 179.5 92.4 14.16 26 WQJL312 38.12577 121.8346 38.02125 121.9878 92.4 179.5 13.99 27 WQJL312 38.12577 121.8346 38.17122 121.8461 120.7 68.2 5.75 28 KBK64 37.9427 121.8852 38.39961 121.9213 597.4 49.7 24.36 29 KEZ84 38.40322 122.108 37.92603 121.2749 852 44.2 31.77 30 KEZ93 37.92603 121.2749 38.40322 122.108 44.2 852 31.39 31 KMD34 37.8813 121.9155 38.57572 121.4977 1179.5 85 30.62 32 KMD35 38.57575 121.4977 37.8813 121.9155 85 1179.5 30.90 35 KNF41 37.9427 121.8852 38.52572 121.3883 597.4 40.2 29.36 36 KNG36 38.39961 121.9213 37.9427 121.8852 49.7 597.4 24.85 37 KNG40 38.52572 121.3883 37.9427 121.8852 40.2 597.4 29.58 39 WAL352 38.58433 121.4772 37.81131 121.8036 42.7 778.7 31.41 40 WBB723 38.41406 122.1149 37.93464 121.2374 853.4 13.7 85.59 42 WGX449 37.89325 121.9002 38.54322 121.4291 1090.3 29.6 53.44 43 WGX450 38.54322 121.4291 37.89325 121.9002 29.6 1090.3 54.06 45 WHO968 38.28544 121.8338 37.88214 122.2338 35.7 553.3 26.62 46 WHO968 38.28544 121.8338 37.88269 122.2208 12.8 579.4 26.44 47 WHY635 37.88277 122.2208 38.24722 121.5019 587.1 -- 28.30 E24 49 WKL76 37.81131 121.8036 38.58433 121.4772 783.3 42.7 31.79 50 WLB208 37.88269 122.2208 38.28544 121.8338 579.4 12.8 25.90 51 WLS839 38.40878 122.1105 37.98908 121.2863 883 21 82.52 52 WLS856 37.98908 121.2863 38.40878 122.1105 21 883 82.92 60 WPOQ470 37.8927 121.8991 38.265 121.4911 1108.8 -- 17.91 61 WPOT265 37.88172 121.9191 38.60625 121.4431 1128.5 33.5 30.94 62 WPZU838 38.60917 121.5556 37.88158 121.9191 36.6 1101.1 30.70 63 WPZU839 37.88158 121.9191 38.60917 121.5556 1101.1 36.6 30.54 65 WQAP211 37.88158 121.9191 38.60917 121.5556 1101.1 36.6 30.24 66 WQHV882 38.60917 121.5556 37.88172 121.9191 36.6 1107.5 32.88

Table 1 – Active Microwave Links in/near Shiloh II Project Area

Yellow = Potential impact; please verify coordinates on-site and notify microwave licensee. * The yellow turbines shown in this column according to this analysis do not encroach on a microwave WCFZ, but nevertheless are close enough to a path to warrant further impact assessment requiring a land survey of the path endpoints.

Additional details on the above microwave links are shown in the following figures.

Microwave links whose status is listed as “cancelled” (“C”) or “expired” (“E”) are not included in Table 1 and have not been evaluated for turbine impact.

If the endpoints of the microwave links are located exactly according to their FCC licenses, none of the proposed turbines as they are currently sited will have an impact on any active microwave path. Impact is defined as non-penetration of the Worst Case Fresnel zone. For the turbines that are within 100 meters of the WCFZ of a microwave path (indicated in yellow in Table 1), it is recommended that the geographic coordinates and heights of the microwave antennas be determined by a land surveyor.

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It should be noted that earth station satellite links have not been included in this study.

In some cases, a turbine may be in the microwave path, but is well below the microwave beam. These situations are not indicated in Table 1.

The details for each turbine that is near a microwave path are identified below:

Turbine B164

4 As with all of these detailed figures, the clearance shown is dependent upon verification of endpoint coordinates and antenna heights.

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Turbine B17

Turbine B18

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Turbines E13 (background) & E14

Turbines C26 & C24 (behind and to left of C26)

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Turbines C27, C35 and C37

Turbine F6

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Turbine E24

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III. ANALYSIS OF FIXED RADIO FACILITIES

There are 20 licensed land mobile stations identified from the FCC’s database that fall within the search area (within two miles beyond the project boundary). They are shown in Table 2 following: Height Predicted Freq Call Sign Latitude Longitude AGL Turbine License Name MHz. (m) Impact WQHG573 38.14778 121.8148 38 None 464.5875 Nextera Energy WSL759 38.15103 121.7069 17 None 154.92 California State KAW894 38.15936 121.7058 34 None 154.28 Solano County KAW894 38.15936 121.7058 15 None 154.28 Solano County KME452 38.15103 121.7069 18 Not Significant 155.49 CSI KNDJ357 38.15103 121.7069 18 Not Significant 154.83 WNST617 38.10603 121.701 20 None 47.08 California State WPRH524 38.22028 121.8681 19.8 None 462.5 Radio Licensing WNLZ654 38.2163 121.8486 8 None 151.22 California State KMA712 38.16409 121.7313 20 Low: F6,F7,F8 48.72 Hess Communications Corp KGV368 38.16436 121.7072 11 None 155.085 Solano County WNGP414 38.09297 121.8869 4 None 169.475 California State WPDE295 38.20492 121.8911 13 None 161.355 Bay Elec Railroad WPGR390 38.16047 121.6938 13 None 811.7375 California State KNCY382 38.14186 121.7016 12 None 152.975 Mayhood Ranches WPKN375 38.15492 121.6911 7 None 154.755 CSI Telecom WNGR827 38.15103 121.7069 12 None 467.95 Sacramento Cty KNJ85 38.15936 121.6861 4 None 169.575 California State WPXE984 38.18917 121.8153 26.8 None 851.1625 Nextel Of Cal WPYI546 38.17361 121.6753 38.4 None 851.0375 Nextel Of Cal

Table 2 – Non-Broadcast Fixed RF Facilities in and near Shiloh III Area

According to the presently available information, only one of the facilities tabulated above will be within significant impact range of the planned turbines (highlighted above). Turbines F6, F7 and F8 surround land mobile facility KMA712, and could combine to result in a minor amount of time-variance to the HF (low frequency) carrier. It is suggested that notification be made to this licensee. Land mobile facilities listed as cancelled or expired have not been evaluated for possible turbine impact.

The maps of Figures 2, 3 and 4 detail the locations of the land mobile facilities in and near the Shiloh III property. A close-up of station KMA712 and the surrounding turbines is shown in Figure 5.

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There can be occasional instances of service areas being disrupted by rotating turbine blades in the path between the transmitter and receiver of the land mobile or public safety facility, but this is not expected to be a significant problem in this case.

Figure 5 – Land Mobile Station KMA712 and Turbines F6-F8

Other Fixed Location Facilities

It is recommended that cellular and PCS antennas be searched for during the physical site visits, since many of the antennas are not individually tabulated in the FCC records.

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IV. ANALYSIS OF BROADCAST FACILITIES

4.1 AM Stations

A search of the FCC’s database revealed no AM facilities within the required notification distance of 3 kilometers beyond the project area boundaries. In fact, there are no AM facilities within 40 kilometers of the center of the turbines. The AM radio station nearest to the project area is KTKZ in Sacramento. The KTKZ transmitter site is about 40 kilometers from the nearest planned turbine.

There should therefore be no reasonable expectations of disruptions in transmitted radiations on the AM band due to the presence of the turbines. Occasionally, depending upon ground conditions, local AM receivers may experience slight signal changes due to local effects, but such anomalies are not recognized by the FCC or the standards of good engineering practice.

4.2 TV Broadcast Facilities

The rotating blades of a wind turbine have the potential to disrupt over-the-air broadcast TV reception within a few miles of the turbine, especially when the direct path from the viewer’s residence is obstructed by terrain. This is manifest in an analog TV picture by a flickering or tearing of the image in time with the blade rotation, which is caused by signals reflected by the blades arriving at the viewer’s TV antenna at the same time as the direct signal. This is known as “multipath interference.” However, as turbine manufacturers have replaced all-metal blades with blades constructed of mostly nonmetallic materials5, this effect has been reduced. Also, the new generation of digital TV receivers is better equipped to deal with multipath interference (which is manifested by “pixilating” or “freezing” of the digital picture) than analog TV sets, as special circuitry is employed to suppress the reflected signal. Occasionally, however, multipath interference from one or more turbines can cause video failure in digital TV receivers, especially if the receiver location is in a valley or other place of low elevation.

The authority to transmit analog TV signals ended on June 12, 2009. For this reason, analog facilities have not been considered in these analyses. The TV facilities listed in Table 3 have been identified as placing a predicted FCC primary service signal over all or most of the turbine area.

5 Modern turbine blades are usually constructed from glass-reinforced plastic (GRP), although they usually contain some metal for strengthening, balance and grounding.

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Network Power Ant. Height Distance Azimuth Off-Air Call Sign Channel City of License Affiliate (KW) (m HAAT) (km) (°T) Quality KVIE-DT (CP) PBS 9 Sacramento 33 596.8 26.3 61.7 Good KXTV (CP) ABC 10 Sacramento 34.5 611.9 25.2 69.2 Good KTNC-DT (CP) Estrella TV 14 Concord 40 962 33.5 202.8 Good KMAX-TV CW 21 Sacramento 850 581.2 27.2 64.4 Good KOVR-TV CBS 25 Stockton 760 591 25.2 69.2 Good KTFK-DT (CP) TeleFutura 26 Stockton 850 595 25.2 69.2 Good KCRA-DT NBC 35 Sacramento 1000 462 25.5 67.5 Good KTXL-DT (CP) Fox 40 Sacramento 950 601 26.3 61.7 Good K45HC (Xlator) -- 45 Sacramento 150 - 27.2 64.4 Fair KQCA-DT MyNetworkTV 46 Stockton 600 580 27.2 64.4 Good KSPX-DT ION 48 Sacramento 1000 489 27.2 64.4 Good KGO-DT (CP) ABC* 7 San Francisco 23.8 519 74.9 233.2 Fair KNTV-DT NBC* 12 San Jose 103.1 376.6 78.6 228 Fair KUVS-DT Univision 18 Modesto 500 555 91.8 92.6 Poor KOFY-DT Ind 19 San Francisco 383 418 74.9 233.2 Fair KTSF Ind 27 San Francisco 500 403.4 78.6 228.1 Poor KPIX-DT CBS* 29 San Francisco 1000 401 74.8 233.2 Fair KQED PBS* 30 San Francisco 777 437 74.9 233.2 Fair KMTP-DT (CP) Ind 33 San Francisco 500 496 74.9 233.2 Poor KRON-DT (CP) MyNetworkTV* 38 San Francisco 1000 511.7 74.9 233.2 Fair KCNS-DT Ind 39 San Francisco 1000 428 74.9 233.2 Fair KKPX-DT ION* 41 San Jose 1000 418 78.5 228.1 Poor KCSM-DT PBS* 43 San Mateo 536 428 74.9 233.2 Poor KTVU (CP) Fox* 44 Oakland 400 512 74.9 233.2 Poor KBCW CW* 45 San Francisco 400 446 74.9 233.2 Poor

Table 3 – Digital TV Stations to Serve Project Area * Network Duplicated

Solano County is split between the Sacramento-Stockton-Modesto CA and San Francisco- Oakland-San Jose, CA Designated Market Areas (DMA) according to Nielsen Media Research. However, it is evident that the Shiloh III area is served primarily by the Sacramento and Stockton stations, since their transmitters are much closer than those of the San Francisco and Oakland stations.

There is some possibility of video disruption of Sacramento-area and San Francisco-area TV signals at residences in and near the project boundary, especially those that have to point their outdoor antennas through the turbine area (NE for Sacramento, SW for San Francisco), or that utilize “rabbit ear” antennas, or older DTV receivers. Most of this effect should be dissipated for locations up to 2 to 3 miles of a turbine, but some residual problems could be noted for DTV receivers that are located below the grade level at the turbine base. For those TV stations for

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which off-air reception is labeled as “Good” in Table 3, approximately 10% of receiver locations may be affected to some extent within 3 miles of a large turbine. The usual effect is intermittent “pixilation” or freezing of the digital TV picture. This estimate is based upon Evans’ experience with similar turbine farms.

In the opinion of this consultant, the number of instances of turbine disruption to over-the-air TV could be relatively numerous but should be manageable. Mitigation would consist of the installation of a rooftop high-gain antenna in the nominal case, and providing a satellite receive dish or cable hookup in the worst case.

According to this engineer’s calculations, there are about 2,240 households within an area likely to be affected. Based on the 10% criteria described previously, and conservatively estimating that 50% of the households rely on over-the-air TV programming, it is most likely that up to 112 HDTV receiving locations may be affected. Mitigation costs would be approximately $200 per location for an upgraded outdoor antenna, or $600 per year per location for a satellite or cable subscription.

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4.3 FM FACILITIES

The full-service FM stations listed in Table 5 place a predicted primary signal over most or all of the turbine area.

Freq. City of Power Ant. Height Dist. Azimuth Call Sign Format (MHz) License (KW) (m HAAT) (km) (°T) KEAR Religious 88.1 Sacramento 8.4 303 25.5 67.5 KQED News/talk 88.5 San Francisco 110 387 78.5 228.4 KXPR Classical 88.9 Sacramento 50 150 26.6 61.5 KLRS Christian contemp. 89.7 Lodi 2.5 487 26.3 61.7 KVHS Active/New rock 90.5 Concord .41 137 24.9 234.5 KRVH Christian 91.5 Rio Vista .05 31 6.5 95.2 KASK Religious 91.5 Fairfield .075 198 26.3 312.5 KKDV Adult contemp. 92.1 Walnut Creek 3 24 39.9 223.8 KRZZ Regional Mexican 93.3 San Francisco 47 150 57.3 212.4 KPFA Div. mus., pub. affairs 94.1 Berkeley 59 405 51.3 230.4 KYLD Urban contemp. 94.9 San Francisco 3 369 78.5 228.4 KUIC Adult contemp. 95.3 Vacaville 149 617 38.9 312.5 KBWF Country 95.7 San Francisco 6.9 393 78.5 228.4 KOIT Adult contemp. 96.5 San Francisco 24 480 74.9 233.2 KISQ Oldies 98.1 San Francisco 75 309.6 72.5 241.9 KSOL Spanish, Mexican regional 98.9 San Francisco 6.1 409 74.9 233.2 KVYN Adult contemp. 99.3 St. Helena 6 79 56.9 301.6 KMVQ Rhythmic adult contemp. 99.7 San Francisco 40 396 78.5 228.2 KIOI Adult contemp. 101.3 San Francisco 125 354 78.5 228.4 KDFC Classical 102.1 San Francisco 33 319 72.5 241.9 KBLX Adult contemp., news 102.9 Berkeley 6.6 393 78.5 228.3 Adult contemp., jazz fusion, KKSF 103.7 San Francisco 7.2 461 74.9 233.2 new age KFOG Rock 104.5 San Francisco 7.1 459 74.9 233.2 KITS New rock alternative 105.3 San Francisco 15 366 78.5 228.3 KMEL Christian 106.1 San Francisco 69 393 78.5 228.4 KSTN Spanish 107.3 Stockton 8.1 491 37.6 181.4 KSAN Classic rock 107.7 San Mateo 8.9 354 78.5 228.3

Table 4 – FM Stations Serving Project Area

Most of the stations located less than 70 kilometers from the turbine area should continue to be receivable without a significant impairment. Because of the “capture effect” supported by the “discriminator” in FM receivers, disruptions to these facilities are not expected. Although the received signal may vary with the blade rotation at some receive locations in the immediate area, good quality FM receive radios will most likely factor out such time-varying signals.

Some problems can be expected with respect to the San Francisco stations, if they have listeners in the turbine area. In those relatively few cases where significant impact is caused, home FM radios could be connected to the rooftop TV receive antennas to pull in a stronger direct signal.

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V. CONCLUSIONS

1. The Shiloh III turbines as they are presently sited clear the known licensed microwave paths as described in the FCC database. However, further verification, via land survey, is recommended for several microwave links that are close to turbine sites. Any turbines that are determined to cause blockage should be moved.

2. According to the FCC database, there are no known licensed land mobile transmitting sites within the immediate vicinity of any of the turbines. However, one facility may be slightly impacted because of a cascaded effect due to three wind turbines (KMA712). The licensee, Hess Communications Corporation, should be notified of the construction of the nearby turbines. Other land mobile operations will likely not be adversely affected, provided that their transmitters are located exactly as per their FCC licenses.

3. Based upon FCC database information, no significant impact is expected to the reception of most FM broadcast facilities. A few receive locations may experience signal fluctuations in time with the blade rotors with respect to the turbine array, but the receiver automatic gain control should be able to manage these variations. In a few cases, it might be necessary to reconfigure radio antennas using outside TV antennas.

4. Direct over-the-air reception of some full-power digital TV stations may be disrupted, requiring mitigation to up to 112 households as detailed in Subsection 4.2.

5. Mitigation measures are expected to be available for all broadcast reception anomalies, with satellite or cable service and/or receiver upgrades providing the worst-case solution.

Respectfully Submitted,

B. Benjamin Evans, P.E. RF Impact Consultant

December 9, 2009

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Appendix G Shadow Flicker Study

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Shadow Flicker Study for the Shiloh III Energy Project

CSRP0026-A

CONFIDENTIAL

December 8, 2009

Prepared for:

enXco, Inc. 700 La Terraza Blvd Suite 200 Escondido, CA 92025

DNV Global Energy Concepts Inc. 1809 7th Avenue, Suite 900 Seattle, Washington 98101 USA Phone: (206) 387-4200 Fax: (206) 387-4201 www.globalenergyconcepts.com www.dnv.com Shadow Flicker Study for the Shiloh III Wind Energy Project CSRP0026-A

Approvals

December 8, 2009 Prepared by Hugh Turnbaugh Date

December 8, 2009 Reviewed by Sarah J. Meyer Date

Version Block Version Release Date Summary of Changes A December 8, 2009 Original

DNV Global Energy Concepts Inc. i December 8, 2009 Shadow Flicker Study for the Shiloh III Wind Energy Project CSRP0026-A

Table of Contents

EXECUTIVE SUMMARY ...... 1 INTRODUCTION...... 2 BACKGROUND ...... 2 SHADOW FLICKER...... 2 IMPACTS...... 4 MODELING METHODOLOGY...... 5 RESULTS ...... 8 CONCLUSIONS ...... 11

DNV Global Energy Concepts Inc. ii December 8, 2009 Shadow Flicker Study for the Shiloh III Wind Energy Project CSRP0026-A

List of Figures

Figure 1. Illustration of the Impact of Relative Elevation on Shadow Flicker...... 4 Figure 2. Cloud Cover Data Locations Relative to Shiloh III Project Site...... 7 Figure 3. Shiloh III Hub-Height Wind Rose (Percent of Time) ...... 8 Figure 4. Shadow Contour Map of Shiloh III Wind Project...... 9

List of Tables

Table 1. Shadow Flicker Frequency of the REpower MM 92 – 2 MW...... 4 Table 2. Reference Cloud Cover and Sunshine Probability for Shiloh III ...... 7 Table 3. Potential Shadow Flicker Impact Summary ...... 10 Table 4. Potential Shadow Flicker Impact Along State Route 12 ...... 11

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Executive Summary

DNV Global Energy Concepts Inc. was retained by enXco, Inc. to conduct a Shadow Flicker Study of the Shiloh III wind energy project (the Project), which is proposed for 65 wind turbines within the Montezuma Collinsville Wind Resource Area. This report summarizes only the shadow flicker impacts related to these 65 turbines.

Shadow flicker caused by wind turbines is defined as alternating changes in light intensity due to the moving blade shadows cast on the ground and objects (referred to as receptors), including windows at residences. Shadow flicker associated with wind turbines can cause disturbances to residents if the orientation of the home and the turbine are such that the residence experiences significant periods of shadow flicker impact.

Shadow flicker from wind turbines is affected by several factors including season, time of day, surrounding terrain and obstacles (including vegetation), cloud cover, distance from the turbine(s), turbine size, and wind speed and direction.

The WindPRO modeling software package was used to assess the shadow flicker impact for the area surrounding the Project, including adjacent residences. Of the 21 near-by residences identified by enXco and evaluated in the model, 18 are expected to experience shadow flicker impacts. The maximum impact at these residences is estimated to be 97 hours of shadow flicker annually at the Rogales residence.

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Introduction

DNV Global Energy Concepts Inc. (DNV-GEC) was retained by enXco, Inc. to conduct a Shadow Flicker Study of the Shiloh III wind energy project (the Project).

The Project is located approximately 50 miles (80 km) southwest of Sacramento, California, and 64 miles (102 km) northeast of San Francisco, California. The Project will consist of 65 REpower MM 92 2.0-MW turbines – 57 with a hub height of 78.5 m and 8 with a hub height of 68.5 m.

In certain situations the flickering shadow effect created by the wind turbine blades moving across the sun can disturb residences located in the vicinity of the wind farm. This study explains the shadow flicker effect with regard to wind turbines and presents results of an impact analysis carried out for the residences in the vicinity of the Project.

Background

Shadow Flicker Shadow flicker caused by wind turbines is defined as alternating changes in light intensity due to the moving blade shadows cast on the ground and objects (referred to as receptors), including windows at residences. Shadow flicker typically occurs when a receptor is in a position where the wind turbine blades interfere with low-angle sunlight (i.e., the turbine blades pass through the path between the sun and the receptor). Shadow flicker associated with wind turbines can cause disturbances to residents if the orientation of the home and the turbine are such that the residence experiences significant periods of shadow flicker.

The shadows cast by wind turbines will vary with several factors including season, time of day, surrounding terrain and obstacles, cloud cover, distance from the turbine(s), turbine size, and wind speed and direction. These factors can impact the number of hours that a given receptor will experience shadow flicker as well as the intensity of the shadow flicker which is defined as the relative contrast between the presence and absence of a shadow at a given location.

The height of the sun in the sky varies by season, as does the time and location at which it rises and sets. In the winter, the sun rises late in the southeast, travels in a low arc across the southern sky in the northern hemisphere, and sets early in the southwest. Because it is so low in the sky, it casts longer shadows. In the summer, the sun arcs through the sky at its highest angle, and casts the shortest midday shadows. However, in the summer, the sun also rises earliest and sets latest, and covers a wider range of directions, from the northeast around the south to the northwest. Therefore, the summer sun casts shadows that span a broader direction range than in other seasons, and its early sunrise and late sunset create shadows earlier in the morning and later in the evening than in other seasons.

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The lateral extent of the blade shadow depends on wind direction, as the wind turbines yaw to face into the wind during operation. For example, during westerly winds, the turbine rotor will face to the west, and a relatively small shadow would be cast on a receptor if the sun is in line with the plane of the rotor, as it is at midday in the winter (sun from the south and lower in the sky). In these cases, the rotor shadow will be in the shape of a narrow ellipse and virtually no shadow flicker will be observable. However, when the sun is low in the sky and perpendicular to the rotor plane, a larger area of moving blade shadows will be cast on the ground. In these cases, the ellipse will be wider. Generally, a southern or northern wind will have minimum shadow impact because the widest shadows would be cast at midday when shadows are also the shortest (closest to the wind turbine) due to the sun’s position high in the sky. Conversely, the greatest potential for shadow flicker impact occurs when winds come from the east or west early or late in the day. Additionally, shadow flicker does not occur when the turbines are not spinning. Therefore, when wind speeds are below the operating range for the turbine, shadow flicker is non-existent.

The size of the wind turbine and the relative position of the turbine relative to the receptor have a significant impact on shadow flicker. A larger rotor diameter obviously results in a larger area within which the blades will cast a shadow. Additionally, the portion of the blade that passes between the sun and the receptor will have varying impacts on the intensity of the shadow flicker due to the variation in width of the wind turbine blade from the widest point near the hub to the narrowest point at the tip. As viewed from the same location, a larger section of the blade will cover a greater portion of the sun than a smaller section of the blade resulting in a higher intensity shadow (greater reduction in the amount of light reaching the receptor). Shadows become less sharp (more diffuse) as distance increases between the shadow-casting object and the receptor. When considering shadows cast by objects at a long distance from the receptor, at a sufficient distance no noticeable shadow forms at all because the object does not significantly block the sun’s light. Instead, light diffracts (or bends) around the edges of the object, and the object itself appears relatively small compared to the apparent size of the sun. The elevation of a receptor relative to the turbines impacts the angle at which the sun is shaded at that location. For example, if the receptor is located at a lower elevation than the turbine, the position in the sky at which the sun would cause shadow flicker at the receptor is higher relative to that for a receptor located at the same elevation as the turbine. This is illustrated in Figure 1 below. In Figure 1, the sun must be in Position A to cause shadow flicker at House A, whereas the sun must be in Position B to cause shadow flicker at House B. At Position A, the sun is higher in the sky and more intense than at Position B resulting in more intense shadow flicker.

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Figure 1. Illustration of the Impact of Relative Elevation on Shadow Flicker

Shadow flicker is strongest when the sun is not obscured by clouds. Shadows may still be cast on cloudy days; however, they are much more diffuse and the shadow flicker intensity is greatly reduced. Other obstructions such as vegetation can affect the shadow flicker at a receptor by blocking or diffusing the shadow cast by a turbine and eliminating or reducing the intensity of the shadow flicker. The analysis provided in this report does not evaluate the flicker intensity, but rather focuses on the total amount of time (hours per year) that shadow flicker can potentially occur at receptors regardless of how intense the shadow flicker is.

Impacts Two types of concerns have been raised regarding shadow flicker: 1) annoyance and 2) possible epileptic seizures. The frequency of shadow flicker will typically be in the 0.5 to 1.0 Hz range regardless of the turbine selected. Table 1 provides specifications for the REpower MM 92 – 2 MW wind turbine. The frequency will be slower when turbines are below cut-in speed (when they often turn slowly in the slight breeze or just stand still).

Table 1. Shadow Flicker Frequency of the REpower MM 92 – 2 MW

RPM Range Frequency Range (Hz)1 Turbine Model Low High Low High REpower MM 92 – 2MW 7.8 15.0 0.4 0.8 [1] (RPM/60) x 3 blades

According to the American Epilepsy Foundation, the frequency of flashing light that is most likely to cause seizures to epileptics varies from person to person. Generally, flashing lights most

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likely to trigger seizures are between the frequency of 5 to 30 flashes per second (Hz).1 This is well above the maximum frequency effect from turbines, which is usually less than 1 Hz.

Modeling Methodology

Shadow flicker impacts were calculated for the Project area using WindPRO software. The WindPRO model simulates the path of the sun over the course of the year and assesses at regular intervals the possible shadow flicker across a receptor based on the operational hours at each wind turbine, wind direction, and sunshine probability statistics. The model results are mapped to show the areas of the Project area that are impacted by shadow flicker. Additionally, the model also calculates the number of hours of shadow flicker impact at specific receptor locations. The shadow-flicker model uses the following inputs: • Turbine locations • Shadow flicker receptor locations (homes in the area) • Elevation data (USGS DEM) • Turbine rotor diameter • Turbine hub height • Total turbine operational hours by direction • Monthly sunshine probability

For this analysis, a worst case scenario is modeled in addition to a more realistic scenario. For the worst case scenario, it is assumed that the sun is always shining from sunrise to sunset, the rotor plane is always perpendicular to the line from the turbine to the sun, and the turbine is always operating. Furthermore, specific local conditions which may further reduce shadow flicker impacts such as vegetation and cloud and fog patterns are not taken into account. This scenario assumes windows are situated in direct alignment with the turbine-to-sun line of sight. Even when windows are so aligned, the analysis does not account for the difference between windows in rooms with primary use and enjoyment (e.g., living rooms) and other less frequently occupied or unoccupied rooms or garages. For the more realistic scenario, the model incorporates cloud cover statistics, the wind direction (yaw direction), and whether or not the turbines are operating.

As the sun approaches the horizon, it is less intense and therefore the shadow influence is reduced. The model does not calculate shadow influence when the sun is at or below an angle of 3° above the horizon. This 3° assumption corresponds to approximately 30 minutes after sunrise and 30 minutes before sunset. Also, the model does not calculate shadow flicker, when less than 20% of the sun is masked by the turbine blade. It is assumed that when less than 20% of the sun is masked by the turbine blade, light diffracts (or bends) around the edges and the difference

1 American Epilepsy Foundation: https://www.epilepsyfoundation.org/about/photosensitivity/index.cfm

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between what is lightly-shaded and what is darkly-shaded is so small that flicker is no longer perceptible.

Certain assumptions applied in the WindPRO model, regardless of the scenario, are generally conservative, and err on the side of over-predicting shadow impacts. For example, cloud cover tends to be greater in the mornings and evenings than it is at midday, and mornings and evenings are typically the periods of greatest shadow flicker impact. Cloud cover, however, is input into the model as monthly averages which yields cloud cover during the mornings and evenings that is on average less than actual cloud cover during these periods, resulting in the model calculating a greater number of hours of shadow flicker impact. Also, as the distance from the turbine increases, the intensity of the shadow cast by the turbine blade decreases. However, the WindPRO model makes no distinction between shadow flicker that is barely noticeable or clearly distinct.

To assess cloud cover at the Project site, a review of long-term data from the National Climatic Data Center yielded cloud cover data from Sacramento, California; San Francisco, California; and Stockton, California.2 These data sets include mean monthly cloud cover data averaged over 49, 68, and 46 years, respectively. Monthly data are presented as mean days per month characterized as “Clear,” “Partly Cloudy,” and “Cloudy” between sunrise and sunset. “Clear” is defined as 0-2 eighths of the sky being obstructed by cloud cover, “Partly Cloudy” specifies clouds in 3-6 eighths of the sky, and “Cloudy” represents 7-8 eighths of the sky being cloud covered. The data from Sacramento, San Francisco, and Stockton are comparable, indicating that the sky is “Cloudy” during daylight hours approximately 27%, 29%, and 28% of the time on an annual basis, respectively. The project area is located between the three cities (see Figure 2), thus an average of cloud cover data was calculated to represent the sky cover at the project area. From these data, monthly sunshine probabilities were derived (as 100% minus percent cloud cover) and applied in the model as shown in Table 2.

2 Comparative Climatic Data for the United States through 2008, National Climatic Data Center: http://www1.ncdc.noaa.gov/pub/data/ccd-data/CCD-2008.pdf

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Figure 2. Cloud Cover Data Locations Relative to Shiloh III Project Site

Table 2. Reference Cloud Cover and Sunshine Probability for Shiloh III Mean Days of "Cloudy" Sky Cover Shiloh III Sacramento, San Francisco Stockton, Sunshine Month CA Airport, CA CA Probability January 19 15 19 45% February 13 13 15 53% March 12 13 13 60% April 8 10 10 70% May 5 8 5 80% June 2 5 3 89% July 1 3 1 94% August 1 3 1 94% September 2 4 2 91% October 6 7 6 80% November 12 11 12 61% December 17 14 18 49% Annual 100 105 104 72%

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enXco provided the operational and wind direction data used in this analysis which were based on data collected from a meteorological tower at the Project site that was in operation from October 1995, through October 2008. In determining operational turbine hours, only wind speeds between rated cut-in (3.0 m/s) and cut-out (24 m/s) were considered. This equated to approximately 87% of time on an annual basis. A wind rose graph showing the percent of time the wind comes from each of twelve 30º direction sectors is presented in Figure 3. This wind rose corresponds approximately to the percent of time that a wind turbine at the Project would be yawed in each direction (i.e., facing the wind). As shown in the wind rose, the wind comes primarily from the west-southwest, indicating that wind turbines at the Project will face this direction most of the time.

Figure 3. Shiloh III Hub-Height Wind Rose (Percent of Time)

Results

The model results are mapped and presented as shadow flicker contours in Figure 4. This shows the location of all 65 wind turbines and the extent to which shadow flicker may impact the Project area. The lines shown represent an equal number of hours per year of shadow flicker perception. Generally, the potential shadow flicker impacts extend farthest to the east-southeast and west-southwest of the turbines. Note that a residence outside the purple line is expected to observe less than 30 hours of shadow flicker during the year. A residence located in the area between the purple and green lines, 30 to 50 hours per year; between the green and blue lines, 50 to 100 hours per year; and within the blue line more than 100 hours per year.

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Figure 4. Shadow Contour Map of Shiloh III Wind Project

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Also shown in Figure 4, are the locations of 21 residences enXco identified as being inside or within 1,000 ft of the project boundary. DNV-GEC calculated the duration of potential shadow flicker at each residence. The model defines each receptor as a 1 square-meter window 1 meter above ground level. The model considers each receptor as omni-directional, thus producing shadow-flicker results regardless of the direction of the actual windows of the residences. This is a conservative approximation and will tend to over-estimate the shadow flicker impacts. A summary of the worst-case and the more realistic results are presented in Table 3.

Table 3. Potential Shadow Flicker Impact Summary Days of Total Total Potential Annual Max Hours Mean Hours Annual Impact per Hours per Day per Day Hours Year (Worst (Worst (Realistic (Realistic ID Residence (Worst Case)1 Case)1 Case)1 Case)2,3 Case)3 A McCosker 68 45 0.93 0.06 20 B Meyer 2 141 18 0.32 0.03 9 C Meyer 1 114 15 0.28 0.02 8 D McCormack 206 38 0.40 0.05 18 E McColgan 109 55 0.73 0.04 14 F Unknown 32 2 0.07 0.00 0 G Hempstead 104 29 0.63 0.02 9 H Unknown 6 0 0.03 0.00 0 I Catty 122 35 0.53 0.03 13 J Industrial Building 83 8 0.27 0.01 3 K Threlfall 303 127 1.03 0.13 48 L Mahoney 220 88 0.68 0.12 43 M McCormack 108 23 0.40 0.03 10 N Mayhood 194 108 0.97 0.12 43 O Unknown 27 1 0.08 0.00 0 P Unknown 62 8 0.22 0.01 3 Q Peters 57 36 0.95 0.04 16 R Rogales 261 213 1.50 0.26 97 S Giordano 0 0 0.00 0.00 0 T Barclay 0 0 0.00 0.00 0 U Hamilton Ranch A 0 0 0.00 0.00 0 1. Worst-case, not adjusted for cloud cover, yaw position, or still winds. 2. Mean hours per day calculated only on days with potential impact. Days without impact are not factored into the average. Mean hours per day would be much lower if days with no potential impact were factored in. 3. Expected hours of shadow adjusted for cloud cover, yaw position or still winds.

As shown in Table 3, three of the residences (S, T, and U) will not be impacted by shadow flicker. Once adjustments are made for cloud cover, operational time, and wind direction (direction turbines are facing); the model predicts that remaining 18 residences would experience shadow flicker between 0 and 97 hours per year, with a maximum daily impact ranging from just 1.8 minutes (0.03 hours) to 1.5 hours. Exhibit A graphically indicates the days of the year and hours of the day in which shadow flicker impacts could occur. The shaded area on each plot illustrates the time of shadow impact and the color indicates the corresponding wind turbine. enXco requested that DNV-GEC also evaluate the potential shadow flicker along California State Route 12. For this analysis, DNV-GEC modeled receptors at key intersections with roads:

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Olsen, Birds Landing, Currie, and Azevedo. As shown in Table 4, the estimated shadow flicker impacts at these locations are 12 hours per year or less. The shadow contour lines depicted in Figure 4 also show that nowhere along Route 12 are the impacts of shadow flicker estimated to exceed 30 hours per year.

Table 4. Potential Shadow Flicker Impact Along State Route 12

Days of Total Potential Annual Max Hours Mean Hours Total Annual Impact per Hours per Day per Day Hours Year (Worst (Worst (Realistic (Realistic ID Intersection (Worst Case)1 Case)1 Case)1 Case)2,3 Case)3 Intersection 1 V 72 13 0 0 5 (SR12 & Olsen Rd) Intersection 2 W 20 1 0 0 1 (SR 12 & Birds Landing Rd) Intersection 3 X 67 7 0 0 2 (SR 12 & Currie Rd) Intersection 4 Y 112 35 1 0 12 (SR 12 & Azevedo Rd) 1. Worst-case, not adjusted for cloud cover, yaw position, or still winds. 2. Mean hours per day calculated only on days with potential impact. Days without impact are not factored into the average. Mean hours per day would be much lower if days with no potential impact were factored in. 3. Expected hours of shadow adjusted for cloud cover, yaw position or still winds.

Conclusions

The modeling approach used in this analysis is purposefully conservative and shadow flicker impacts may be less than what is presented in this report. For example, existing obstacles such as buildings and vegetation may mask shadow flicker impacts from residences.

Based on the results of this analysis, 18 of the 21 residences are estimated to experience shadow flicker between 0 and 97 hours per year. Although this effect may disturb certain residents, shadow flicker does not present any known health or safety problems and there are no local or national regulations in regard to maximum shadow impacts caused by wind turbines.

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Exhibit A: Shadow Calendar Maps for Shiloh III

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DNV Global Energy Concepts Inc. A-5 December 8, 2009

Appendix H Hazard Zones Resulting from Certain Defined Failures of RePower MM92 Wind Turbines

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Appendix I Assessment of Consistency of Shiloh III Wind Project with Rio Vista Airport Master Plan

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Aviation Technology Solutions

4720 Montgomery Lane Suite 950 Bethesda, Maryland 20814 Voice (301) 941-1460 Website: www.jdasolutions.aero

Assessment of Consistency of Shiloh III Wind Project with Rio Vista Airport Master Plan

JDA has been retained by enXco Development Corporation (enXco) to assess the possible impact of the Shiloh III project on future desired operational changes to the Rio Vista Airport as expressed in the 2025 Airport Master Plan Update for the Rio Vista Municipal Airport (the Master Plan).1 The desired operational improvements called for in the Master Plan are for the purpose of increasing efficiency at the airport and are not driven by safety concerns. The addition of new instrument procedures at an airport improves the overall efficiency of operations at the airport; the Master Plan states that “existing airspace and air traffic procedures and facilities provide for safe, orderly and expeditious flow of traffic.” (Master Plan at 5-7.) These improvements do not impact flight safety in any manner. The Federal Aviation Administration (FAA) is required to design approach procedures that ensure the safety of operations.

The Master Plan is an aspirational document setting forth the airport’s proposed but unfunded improvements to increase efficiency and revenues at the airport. The Master Plan describes a range of proposed operational improvements including, among other things, the lengthening of Runway 7-25, facility improvements, and the addition of new precision instrument procedures. Since the improvements are not intended to improve safety, the impact of the Shiloh III project on the airport’s ability to implement its future improvements is likewise not a safety issue but rather is an economic or efficiency issue. JDA concludes that the Shiloh III project will not impede Rio Vista’s potential implementation of its future Master Plan improvements, assuming that it obtains the funding to proceed. Rather, the development of the Shiloh III project and the envisioned improvement of airport operations under the Master Plan can co-exist.

JDA’s analysis included several variables that could affect the number of turbines that may penetrate the obstacle clearance surface for future flight procedures. The first variable is the design criteria used to construct the flight procedures analyzed. The FAA approved new flight procedure design criteria two years ago (FAA Order 8260.54A). This new criteria superseded the FAA’s old design criteria (FAA Order 8260.48); however, the FAA has not yet updated its automated design tools and will continue to use the old design criteria until its automated tool update is completed (anticipated to occur within the next 12 months). The second variable accounts for two potential improvements to the airport that could result in the lowering of flight procedure minimum altitudes

1 This analysis goes above and beyond the obstruction evaluation that is currently pending before the Federal Aviation Administration (FAA) under Part 77 of Title 14 of the Code of Federal Regulations. The FAA’s analysis will assess whether each of the proposed turbine locations adversely affects existing airport operations.

Aviation Technology Solutions

(Minimum Descent Altitudes [MDAs] and Decision Altitudes [DAs]). The improvements analyzed that could lower the minimum of a potential precision approach are (1) Rio Vista obtaining an FAA accuracy survey of the two existing 225 foot PG&E towers located southeast of the airport and (2) Rio Vista certifying an onsite Automated Weather Observing System (AWOS).

With these variables in mind, JDA analyzed a total of 12 potential precision flight procedures. As explained in greater detail below, the 12 flight procedures consist of alternative analyses of precision approaches (VNAV and LPV) that account for potential airport improvements and the FAA’s old and current design criteria. The analysis concludes that enXco’s and Rio Vista Airport’s objectives can co-exist under the FAA new design criteria which should be implemented in the next 12 months.2

I. Summary of Findings

The variables applied to each type of flight procedure (VNAV or LPV) were:

Design Criteria:

(1) Old (FAA Order 8260.48) Design Criteria; or

(2) Current (FAA Order 8260.54A) Design Criteria;

Airport Conditions:

(1) No Tower Survey and No Onsite AWOS (“Existing Conditions”); or

(2) Either a Tower Survey or Onsite AWOS (“Semi-Improved Conditions”); or

(3) Both a Tower Survey and Onsite AWOS (“Improved Conditions”).

JDA’s results obtained from modeling conducted through the use of proprietary tools are presented in Table 1-1 below.

Existing Conditions Analysis. JDA’s analysis determined that under Existing Conditions, one turbine would penetrate a precision VNAV procedure under the old design criteria. There are no penetrations of a VNAV procedure under Existing Conditions and the current design criteria.

JDA’s analysis determined there would be no penetrations of a precision LPV procedure under either the old and current design criteria.

2 For a more detailed explanation of non-precision and precision approaches and the FAA’s design criteria, please see Appendix A. 2

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Semi-Improved Conditions Analysis.

JDA’s analysis determined that under Semi-Improved Conditions, 12 turbines would penetrate the precision VNAV procedure under the old design criteria as opposed to one under existing conditions. There would be one penetration under the current design criteria.

JDA’s analysis determined there would be no penetrations under Semi-Improved Conditions of a precision LPV procedure under either the old and current design criteria.

Table 1-1 Design Criteria Assessment Summary Comparison

Existing Conditions Old Design Criteria (8260.48) Current Design Criteria (8260.54A) Number of Number of Procedure Penetrations Turbine Penetrations VNAV (450 DA) 1 VNAV (450 DA) 0 LPV (273 DA) 0 LPV (273 DA) 0 Semi-Improved Conditions (Future Surveyed PG&E Towers or Certified AWOS)

Old Design Criteria (8260.48) Current Design Criteria (8260.54A) Number of Number of Procedure Penetrations Turbine Penetrations VNAV (401 DA)* 12 VNAV (401 DA) 1 LPV (273 DA) 0 LPV (273 DA) 0 *Certified AWOS result only. If remote altimeter, then VNAV (450 DA) results apply. Improved Conditions (Future Surveyed PG&E Towers and Certified AWOS)

Old Design Criteria (8260.48) Current Design Criteria (8260.54A) Number of Number of Procedure Penetrations Turbine Penetrations VNAV (401 DA) 12 VNAV (401 DA) 1 LPV (273 DA) 0 LPV (273 DA) 0

Improved Conditions Analysis. The Improved Conditions analysis reached the same conclusions as the Semi-Improved Conditions analysis. JDA’s analysis determined that under Improved Conditions, 12 turbines would penetrate the precision VNAV procedure under the old design criteria as opposed to one under Existing Conditions. There would be one penetration under the current design criteria.

JDA’s analysis determined there would be no penetrations under Improved Conditions of a precision LPV procedure under either the old and current design criteria.

Recommendation. Based on these findings, it is in the best interest of the airport to have the FAA develop a precision RNAV procedure using the FAA’s current design

Aviation Technology Solutions criteria. Rio Vista Airport will achieve a substantial improvement in the efficiency of its operations with only a de minimis interaction with the Shiloh III project.

II. Analysis of Future Airport Operations and Precision Procedures

JDA analyzed the effect of the Shiloh III project on the stated goals in the 2025 Airport Master Plan Update for the Rio Vista Municipal Airport (the Master Plan). The desired operational improvements called for in the Master Plan are for the purpose of increasing efficiency at the airport and are not driven by safety concerns. The Master Plan states that “existing airspace and air traffic procedures and facilities provide for safe, orderly and expeditious flow of traffic.” (Master Plan at 5-7.) The Master Plan also states “the City shall ensure that Airport operations remain compatible with adjacent land uses.” (p. 1-3.) The adjacent wind resource area has been in existence since the early 1980s. Solano County recently confirmed its intention to encourage build out of the wind resource area south of Highway 12 in its 2008 General Plan.

The Master Plan contains the following major goals:

1. Land Acquisition. Acquiring approximately 109 acres of land east and north of the airport for a runway protection zone and general aviation uses such as hangers or repair facilities. The Shiloh III project does not include any of the land proposed to be acquired by the airport for future operations; 2. Runway Extension. Extending Runway 7-25 to the east 1,700 feet in phases to a final length of 5,900 feet to accommodate business jets and large propeller aircraft and moving the runway protection zone for Runway 7-25 to the east to accommodate the runway extension. An extension of Runway 7-25 to the east will have no interaction with the Shiloh III project which is proposed to be located to the west of the airport. Such an extension will move the approach end of the runway farther away from Shiloh III turbines. By shifting the approach end of the runway to the east, the protected obstacle clearance slope will also likely move to east resulting in aircraft crossing the Shiloh III turbines at a higher altitude. Therefore the approach procedures developed for an extended runway will have a lower likelihood of interaction with Shiloh III turbines than the current runway design; 3. Facility Improvements. Various facility improvements including consolidating hangers to south side of terminal area, reserving space for corporate hangers to the north end of terminal; leasing 15,000 square foot hanger to Travis Aero Club; building a wash rack; extending Bauman Rd. to north side of airport; building an extended perimeter service road; improving utilities; and installing an Automated Weather Observing System. The Shiloh III project will have no impacts on the planned improvements to airport facilities or access roads; 4. Slope Preservation. Preserving a 34:1 slope surface ratio for Runway 7-25 and a 20:1 slope ratio for Runway 14-32 within the approach surface for each runway. The Master Plan calls for the protection of approach slopes to each of the runways at the airport. These slopes are based on obstacle identification surfaces established under 14 CFR Part 77.25 and are described as a ratio. The Master Plan calls for the protection of 20:1 and 34:1 slopes. Based on 4

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the approach surface vertical and horizontal dimensions outlined in 14 CFR Part 77.25, none of the proposed turbines penetrate these slopes; and 5. Flight Procedures. Obtaining a precision approach with vertical guidance down to between 250 feet and 300 feet above ground level (AGL) for the airport and cancellation of the VOR procedure by the FAA. JDA developed VNAV and LPV GPS procedures to Runway 25 to determine if the proposed turbines would result in an increase to the otherwise achievable minimum altitudes if the procedures were built by the FAA at some point in the future. Since any new procedures applied for by the airport will likely be developed using the current 2007 design criteria, a stronger focus was placed on the result of that analysis.

a. Analysis of Existing Conditions VNAV and LPV Precision Procedures

Using the old design criteria, JDA developed a two dimensional graphical overlay to determine the proximity of the proposed turbines to the final and missed approach courses. From this overlay, measurements were calculated using a graphical information system (GIS) and then modeled using proprietary Terminal Instrument Procedures (TERPS) modeling tools. These TERPS models provided the vertical height limits (obstacle clearance surface) for each individual turbine. The height of the obstacle clearance surface height was then compared to the proposed AMSL height of each turbine to determine if the height of the proposed turbine was greater than, equal to, or less than the obstacle clearance height. For turbines with proposed heights less than the calculated obstacle clearance height, a finding of “no penetration” was assigned. For turbines with heights greater than the calculated obstacle clearance surface, a finding of “penetration” was assigned.

In order to validate the findings of this study, JDA requested that the FAA Flight Procedures Office in Seattle conduct the same study to determine if the proposed turbines would impact these procedures. JDA then met with the FAA to review the findings. JDA found that its calculated obstacle clearance surface heights were within an acceptable margin of error (+/– 5 feet) of those calculated by the FAA.

Existing Conditions VNAV – The VNAV was analyzed with a 450 foot decision altitude. This decision altitude represents the minimum altitude possible for this type of approach for Runway 25 due to existing obstacles not associated with the Shiloh III project (401 feet) plus a 49 foot penalty required by the FAA due to the lack of a certified onsite AWOS. Under the old design criteria and existing conditions (no tower survey and no onsite AWOS) one Shiloh III turbine would penetrate a VNAV procedure with a 450 foot decision altitude. Under the current criteria that will be implemented in the next 12 months, none of the proposed turbines would penetrate a VNAV approach with a 450 foot decision altitude.

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Table 3-1 Design Criteria Assessment Comparison – VNAV Existing Conditions Current Airport Conditions (VNAV – 450 DA) Old Design Criteria (8260.48) Current Design Criteria (8260.54A) Penetration in Penetration in Turbine feet Turbine feet E13 4 E13 0

Existing Conditions LPV- Under the old design criteria, none of the turbines would penetrate an LPV procedure with a 273 foot decision altitude (250 feet above runway elevation). The 273 foot decision altitude is the minimum altitude possible for this type of approach for Runway 25 due to existing obstacles not associated with the Shiloh III project. Under the current criteria none of the Shiloh III turbines would penetrate the LPV obstacle clearance surface with a 273 foot decision altitude.

Table 3-2 Design Criteria Assessment Comparison – LPV Existing Conditions Current/Future Airport Conditions (LPV – 273 DA) Old Design Criteria (8260.48) Current Design Criteria (8260.54A) Penetration in Penetration in Turbine feet Turbine feet ‐ 0 ‐ 0

b. Analysis of Semi-Improved and Improved Conditions VNAV and LPV Precision Procedures

JDA assessed future VNAV approaches designed under the under semi-improved and improved conditions and found that the penetrations are identical. This is the case because a survey of the PG&E towers would have no effect on the decision altitude for the VNAV procedure; however, certification of Rio Vista’s AWOS would lower the decision altitude by 49 feet to 401 feet.

JDA’s analysis determined that under semi-improved and improved conditions 12 turbines would penetrate the precision VNAV procedure under the old design criteria. There would be one penetration under the current design criteria.

JDA’s analysis also determined there would be no penetrations of a precision LPV procedure under either the old and new design criteria using a 273 foot decision altitude. The 273 foot decision altitude is the minimum altitude possible for this type of approach for Runway 25 due to existing obstacles not associated with the Shiloh III project and is not affected by a tower survey and assumes an onsite AWOS.

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Table 3-3 Design Criteria Assessment Comparison – VNAV Semi-Improved and Improved Conditions Semi-Improved and Improved Conditions (VNAV – 401 DA) Old Design Criteria (8260.48) Current Design Criteria (8260.54A) Penetration in Penetration in Turbine feet Turbine feet E13 50 E13 4 E4 30 E4 0 E9 29 E9 0 E12 27 E12 0 E3 11 E3 0 E8 10 E8 0 E1 7 E1 0 E11 5 E11 0 E2 4 E2 0 E13 4 E13 0 E16 4 E16 0 E15 3 E15 0

Table 3-4 Design Criteria Assessment Comparison – LPV Semi-Improved and Improved Condition Semi-Improved and Improved Conditions (LPV – 273 DA) Old Design Criteria (8260.48) Current Design Criteria (8260.54A) Penetration in Penetration in Turbine feet Turbine feet ‐ 0 ‐ 0

Conclusion

If the Rio Vista Airport applies for new procedures under the current design criteria that will be implemented in the next 12 months, the airport will likely be able to obtain a VNAV procedure with a 405 foot decision altitude or a LPV procedure with a 273 foot decision altitude (250 feet above runway elevation), but in all events the applications will not be hindered by the presence of the proposed Shiloh III turbines. Neither minimum is driven by the Shiloh III turbines, but are instead mainly the result of the two 225 foot PG&E towers to the east of the airport and lower obstacles closer to the east end of Runway 25. The airport should coordinate with the FAA regarding the appropriate timing of its applications for new procedures to ensure that the procedures are designed with the FAA’s new design criteria. To reiterate, this analysis goes above and beyond JDA’s normal scope of analysis since it is looking at future desired operations for the airport, which may improve the airport’s efficiency and economic profitability but are not related to safety issues.

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Report completed on April 23, 2010 by:

Benjamin M. Doyle JDA Aviation Technology Solutions

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4720 Montgomery Lane Suite 950 Bethesda, Maryland 20814 Voice (301) 941-1460 Website: www.jdasolutions.aero

Appendix A

Background on FAA Design Criteria and Commonly Used Flight Procedures

Pilots operating during periods of reduced visibility and low cloud ceilings rely on terrestrial and satellite based navigational aids (navaids) in order to navigate from one point to another. These navaids provide horizontal and vertical guidance to on-board avionics that aid the pilot in locating the runway. The FAA designs, flight checks and publishes instrument approach procedures that not only provide the necessary navigable guidance but also ensure that aircraft remain clear of obstacles and terrain.

a. Design Criteria Status

The FAA has established design criteria for both terrestrial and satellite based instrument approach and departure procedures. These criteria specify the vertical and horizontal dimensions of protected airspace to ensure that aircraft do not collide with obstacles or terrain. Area Navigation (RNAV) for Global Positioning System (GPS) procedure design criteria have been evolving over the past ten years. In December 2007, the FAA issued Order 8280.54, United States Standard for Area Navigation, which superseded and cancelled the prior design criteria for Area Navigation procedures set forth in Order 8260.48, Area Navigation (RNAV) Approach Construction Criteria. Even though the latest design criteria have been in effect for the past two years, the FAA has not yet incorporated the current criteria into its design automation tools. Based on JDA’s discussions with the FAA’s Seattle Flight Procedures Office, it is expected that the current criteria will be implemented in the next 12 months. In the meantime, the FAA continues to design procedures and assess the effect of obstacles on existing procedures using the older, cancelled criteria.

b. Non-Precision Approaches (LNAV and VOR)

With the advent of the Global Positioning System, the FAA has established Area Navigation (RNAV) procedures that are classified as either non-precision or precision type approaches. Published non-precision approach procedures are dependent upon navaid provided horizontal guidance coupled with published minimum descent altitudes. Pilots flying these types of approaches, such as the RNAV (GPS) Lateral Navigation (LNAV) approach, receive a continuous stream of data through on-board GPS systems that let the pilot know whether the aircraft is too far left or right of course. Instead of following a fixed glide slope, the pilot descends to pre-established altitudes at incremental points along the approach. The lowest of these altitudes is termed the minimum descent altitude (MDA) and is the point by which a pilot must visually locate the runway or conduct a missed approach by climbing to a predetermined altitude and

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direction then contacting air traffic control for further instructions. Non-precision approaches are the least accurate types of instrument approaches and therefore normally have the highest minimum descent altitudes.

c. Precision Approaches (VNAV and LPV)

Precision approaches offer both course (horizontal) and glide path (vertical) guidance directly to the aircraft. Unlike the non-precision LNAV procedure, pilots are not required to “step down” from point to point to pre-established altitudes. Instead, pilots follow guidance provided by on-board avionics that allow for a steady descent to an established point at the end of the runway. Precision approaches such as the RNAV (GPS) Lateral Navigation with Vertical Navigation (VNAV) and Localizer Performance with Vertical Guidance (LPV) approaches still have an established minimum descent altitude called a Decision Altitude (DA). The published DA provides pilots an altitude at which they must decide whether a safe landing can be completed or whether a missed approach should be executed.

LPV and VNAV procedures provide a level of accuracy greater than that provided by LNAV procedures. The LPV procedure is the most accurate RNAV (GPS) procedure available for public use. This type of approach will accommodate a decision altitude as low as 200 feet above runway elevation assuming a pristine, obstacle and terrain free environment.