Appendix C. Sound Analysis Methods and Data. Contents. Table of Contents

Transcription

1 Appendix C Sound Analysis Methods and Data Table of Contents Contents C-1: Analysis Methods for Sound... 2 C-2: Royal River / Royal Lake Sound Measurements... 9 C-3: Photos Displaying Location of Sound Source C-4: Model for Sound Decibel Level Decay Rates through Air C-5: Miscellaneous Calculations C-6: Weather and Sound Test Data Final Environmental Impact Statement C-1 Appendix C

2 C-1: Analysis Methods for Sound The focus of this analysis is to compare the difference between alternatives since this is the heart of the EIS (CEQ 40 Frequently Asked Questions on NEPA, Question #7). While additional or more complex data collection or modeling might provide a greater degree of accuracy, the methods described were considered sufficient by resource specialists to highlight the difference between alternatives. Factors Identified in Court Order The following factors identified were identified in the Court Order in considering effects of sound on the BWCAW: 1. New type of sound 2. Additional volume of sound 3. Additional frequency or how often the new sounds would be heard 4. Additional duration of sound To consider these factors, a four step approach was taken to analyze the effects of sound and are described below: A. Field data was collected and field data was used in the analysis whenever possible. B. A model was used to estimate sound levels to cover areas where field data was not collected. This includes additional modeling with the SPreAD-GIS model to check results from the field data (see FEIS Appendix G). C. These data were evaluated to determine the type, volume, frequency and duration of sound. D. Finally, this information informed the disclosure of effects to wilderness character of the BWCAW. A. Field Data Collection Methods Sound Cannot be Measured from Trails that Do Not Exist The approach used for this analysis emphasizes the use of field data, along with basic modeling to estimate effects in areas where data was not collected. There are several considerations that shaped the analysis methods for sound. There is a closed route, an existing route and three potential routes in the project area (see EIS Chapter 2, Sections 2.1 and 2.2). Sound that was present on the Tilbury Trail does not exist now and the sound that would be generated through use of the potential alternatives does not exist now. Snowmobiles may not be driven on routes that do not currently exist. Those facts do not allow a direct measurement of actual snowmobile use on the action alternative trail routes. However, field data was collected where possible by measuring sound from snowmobiles on existing routes, and from broadcasting a recording of snowmobile sound as described below. Field Data Collection Final Environmental Impact Statement C-2 Appendix C

3 A group of nine technicians were trained on data requirements, instruments to be used, the design of the study, and the limitations of the methods. They went into the BWCAW on Royal River and Lake and measured snowmobile sounds during winter conditions. Further detail on the field data collection methods and results may be found in Section C-2. Technicians used an EXTECH HD600 decibel meter to measure the loudest levels of sound using the dba 1 measure, including both natural ambient 2 levels and snowmobile sound when it exceeded the natural ambient level. Section C-2 displays the graphic recordings from the EXTECH plus notes for the sounds on those graphs. The Extech HD600 used in the Sound Test could only record the loudest sound levels present (rated from 30 to 130 dba) which were displayed on the graphs. The human ear (using the Observer Based Source Identification Logging method or OBSIL, Miller 2008) was used by the technicians to note the types of sounds picked up by both the EXTECH, the types of sound in the background and the distance a sound was audible from its source. Distances that sounds were recorded or observed were measured using Global Positioning Satellite (GPS) systems (Trimble Juno SB device) with accuracy of 2-5 meters. The first Royal River Sound Test was completed in January and February of 2009 with a follow up test in March The results can be found in Section C-2. Data collected included the following for each alternative as relevant: The types of sounds within the background, Point samples along the Royal Lake and River area of the BWCAW of ambient levels for background sounds, with and without snowmobiles operating on existing routes, The audible distance 3 of current snowmobile sounds. Point samples in the Royal Lake and River area of the BWCAW where snowmobile sound would be above natural ambient sound level. This included sampling a recording of snowmobile sound broadcast from the Alternative 2 trail location near the wilderness boundary. Additional data collection was completed with a Larson Davis 831 sound level meter in March 2011 for natural ambient sound levels. See FEIS Appendix G for this data. 1 dba refers to A-weighted Decibels, which is considered the best Decibel weighting for sounds discernable by the human ear. 2 Natural Ambient refers to the set of sounds generated by nature (e.g. sounds from wind, water, and birds) and does not include human generated sound such as from snowmobiles or trucks. 3 A source sound may be lower volume than the ambient sound volume, yet still be heard or audible since the sound is of a different type. For example, background sound such as wind may be louder than a snowmobile, yet the snowmobile may still be discerned since it generates a different type of sound than wind does. Final Environmental Impact Statement C-3 Appendix C

4 Sound Levels The analysis uses sound levels (L) measured in two minute points of time. Values for ambient background sounds were averaged over a two minute period (L2min) however the spikes can also be seen on the graphs. Sounds that caused peak values (Lmax) were noted and those peaks for snowmobile sound were used in the analysis. Figure C-1: Example of two minute sound test recording. Alternative 2 sound projection was recorded by sound meter. Large spike was caused by a sniffle. Sound point 7 Trail Recording. 02/05/ :13. Average dba: 41.5 Figure C-1 demonstrates the L2min is 41.5 dba and the sniffle caused an Lmax of 73 dba (not used in calculations). Limitations A trail for the proposed Alternative 2 route does not exist and therefore it was not possible to have a snowmobile in use from which sound could be measured. The sound test methodology included using a devise that recorded a snowmobile traveling at the design speed of the trail. That devise was then connected to a bullhorn type speaker to project the sound of a snowmobile from the Alternative 2 trail route (see Section C-2 for broadcast location and sampling points). The sound level of the recording was played back at the same level as it was recorded (102 dba) but it is not known that the speaker system reproduced the exact quality of snowmobile sound. Technicians conducting the test could not differentiate the recording from a live snowmobile and the volumes were correct so the results were considered adequate. Data points were not collected for every possible location. Snowmobile drivers riding on lakes could travel at various speeds, hence the broadcast levels of dba could be greater or lesser than figures used in calculations for sound decay. Another factor would be the actual Final Environmental Impact Statement C-4 Appendix C

5 route of the snowmobile. There are some limitations in this analysis in that the sound level for a snowmobile was held constant (74 dba at 50 feet equivalent to 105 dba measured at one foot). When considering travel to be on roads, the location is fairly accurate, however when the snowmobilers are on lakes, obviously they could travel on many paths. This analysis projects sound as if the snowmobiles were driving along the lakeshore. The decision to use lakeshore was based on photographic evidence (Section C-3) that snowmobiles often ride within a few feet of the lakeshore. B. Geographic Information System (GIS) and Modeling Methods Several modeling methods were considered for use in the analysis. Consideration was given to complex commercial models that have the ability to perform spectral analysis 4. Spectral analysis can be useful in characterizing ambient sound in environments that have a variety of sound sources, particularly in urban environments. These commercials models are often used in determining methods to reduce sound from urban sources such as airports and freeways. For the South Fowl project, field monitoring has verified that snowmobile sound would be present in the analysis area under all alternatives, including no action. The focus of the analysis is comparing levels of sound between alternatives. The difference between alternatives would be the volume (i.e. sound pressure level) and duration of snowmobile-generated sound. While a spectral analysis would do a good job characterizing the composition of sound in the analysis area, this would be useful information but not necessary for estimating the difference in volume and duration of snowmobile-generated sound between alternatives. Instead, field monitoring was emphasized and supplemented with basic modeling that allowed for a comparison of differences in snowmobile sound between alternatives. The decibel levels and distance measured from field monitoring described above was entered into a GIS to spatially locate and analyze the sound impact zones and determine affected areas for existing conditions as well as proposed trail routes. This included a zone for audible sound and a zone demonstrating the area that motorized sound would be above natural ambient sound levels. Chapter 3 of the EIS displays results of this analysis. Further information on the model used may be found in Section C-4. Figure C-2 below displays an example of a sound decay (i.e. attenuation) curve used in the model. The SPREAD GIS model 5 sponsored by the Wilderness Society was tested and was run for the FEIS. This model was designed specifically to evaluate the effects of motorized noise on natural environments, and methods and results are displayed in Appendix G and referred to in Section 3.2 of the FEIS. This model was used to check the results displayed in Appendices C and D, and Section 3.2 of the FEIS. 4 See Chapter 4, Glossary for a definition of spectral analysis. 5 See for further information on the SPREAD GIS model. Final Environmental Impact Statement C-5 Appendix C

6 Figure C-2: Example Sound Decay Curve used for modeling. Assumptions Proposed trail route Alternative 2 would be used by snowmobiles in typical use today and not other types of motorized equipment such as ATVs since the route would be effectively closed to ATVs in the summer. For Alternatives 3 and 4, the summer motorized use would be the same as No Action. Therefore, the focus is on sounds emitted and measured in the winter. Though various motorized sounds may be present in the background, the sounds of concern that were to be analyzed were those emitted from snowmobiles. The Minnesota Pollution Control Agency Guide to Noise Control in Minnesota (MPCA 1999) states that doubling the number of sound sources (snowmobiles in this case) would add 3 dba to the total measured levels. This would be true for each of the locations including background sounds as well as each of the alternatives. For the purposes of this analysis one snowmobile is assumed to be the source of sound with the exception of the calculations for duration as displayed in Table 3-3 (Chapter 3). Final Environmental Impact Statement C-6 Appendix C

7 Limitations Rates of decay would be different in open air versus through the forest. Note that the only areas where sound would not be affected by trees would essentially be the lakes. The technicians conducting the sound test took specific measurements of decay to no audible sound and decay to natural ambient where the receptor location was Royal River and Lake and the points of origin of snowmobile sound was from the surrounding lakes or the Alternative 2 route location. These measurements served well for the analysis of rates of decay through open air. However, to determine the rate of decay through the forest, the analysis used calculated measurements for decay distances instead of field measurements (see Section C-5). There are several miles of wilderness boundary where snowmobile sound is immediately adjacent and projected into the wilderness. The forest likely has some variability that could affect the rate of sound decay to a small degree. However, work done by Sumara and Tsitsoni, 2007 and Harrison, 1980 suggests that vegetation variability would not measurably affect sound decay. Therefore the calculated measurements used for decay rates where a forest was present were considered adequate. The effect of the cliff face present next to the Alternative 2 route was accounted for through direct measurements of recorded snowmobile sound projected from the route next to the cliff. These data were used for modeling purposes for the entire Alternative 2 route. The cliff would increase the amount of sound projected towards the wilderness, but is not present along the entire Alternative 2 route. Therefore, the analysis conservatively overestimates the amplifying effect of the cliff on the acreage of wilderness affected and the volume of sound impact from Alternative 2. Sound levels were calculated for the impact to homeowners. The terrain is flat on the lake with no vegetation between the sleds and the homes so the model was assumed to be adequate. Alternatives 3 and 4 as they would ascend the hill from the lakes do not exist and the technicians did not have permission from the home owners to set up the test equipment on their land. Models when compared to actual tests for Alternative 2 route underestimated the sound level, therefore we conclude that sound levels received at the home sites is not overestimated. For purposes of comparison, the modeled sound levels were considered adequate. Sound levels for use on Arrowhead Trail were estimated using modeling since snowmobile use on this road is unsafe. MPCA (1999) states that doubling the number of sound sources (from one to two snowmobiles in this case) would add 3 dba to the total measured levels. This would be true for background sounds as well as snowmobiles operating on each of the alternative routes. While a 3 dba increase doubles the sound pressure, MPCA also notes that 3 dba is the human ear s threshold for perceiving a change in sound levels. Assuming the total number of snowmobile riders does not change, and they rode in groups of two, the perceived level of Final Environmental Impact Statement C-7 Appendix C

8 sound would only change slightly (like walking down a road and a car approaches you from behind, you may or may not be able to tell that two cars are coming at you). However the time that snowmobile sound was present would be roughly half the time (again as if you were walking down the road and two cars passed you separately, you d experience twice the sound as two cars passing at once). As stated above, for the purposes of this analysis one snowmobile is assumed to be the source of sound with the exception of the calculations for duration as displayed in Table 3-3, Chapter 3. C. Evaluation of Field Measurements and Modeling The field measurements and modeling were used to answer the following questions about each alternative on three receptors: the BWCAW as an entity, people within the wilderness who might hear the sound, and homeowners on the south side of McFarland Lake: 1. New type of sound. This was determined through field observations and discussions with local residents and recreationalists. 2. Additional volume of snowmobile sound. This was estimated using the field measurements and modeling. The area in which snowmobile sound would be audible, and the area and amount of incremental increase in snowmobile sound above natural ambient sound levels was determined for each alternative. 3. Additional frequency or how often the new sounds would be heard. This was estimated based on knowledge of snowmobile traffic patterns in the analysis area. 4. Additional duration of sound emitted by snowmobiles from the proposed routes. The length of each trail that sound would be audible or above natural ambient was determined using sound level distance measurement. Then those distances were used with estimated snowmobile speeds and the average number of snowmobiles per day to determine the duration of time snowmobile use would be heard (calculations are shown in Section C-5 and results are in Table 3-3, Chapter 3). For the purposes of this analysis, three days were assumed to have snowmobile use (Friday, Saturday and Sunday) with 30 sleds each day. This is based on field observations and discussions with local users. Other days were assumed at zero use. Final Environmental Impact Statement C-8 Appendix C

9 C-2: Royal River / Royal Lake Sound Measurements Royal River Sound Test January/February 2009 Sound tests were conducted on the Royal River in the Boundary Waters Canoe Area Wilderness on 3 separate occasions during January and February of The purpose was to measure the decibel level in the wilderness of a snowmobile s engine running outside the wilderness. The following is a summary of the methods and equipment used, and a summary of the results. Parameters of the Sound Test 1. Three sites were chosen to produce the sound of a snowmobile s engine running at different speeds. One snowmobile was placed on Little John Lake running at a speed of miles per hour. Another snowmobile was placed on North Fowl Lake running at a speed of approximately 40 miles per hour. The third site was on the proposed South Fowl Lake snowmobile trail. Since a snowmobile could not get to this location, a recording of a snowmobile running at 5-10 miles an hour was used. 2. Nine listening points were chosen along the Royal River. These points were chosen in relation to the terrain along the river. Sound points were taken in open bogs, open lakes, where ridges changed direction, and in closed canopy forest. These points also corresponded to the travel route someone would use on their way from John Lake to North Fowl Lake. 3. Each sound point had 4 tests conducted, each test being a 2 minute recording of decibel levels. Test one was the ambient noise of the Royal River with no snowmobiles running. Test two was the running of the snowmobile on Little John Lake. Test three was the playing of the recording of a snowmobile from the proposed snowmobile trail (the location of the recording was a point south of Royal Lake). Test four was the running of the snowmobile on North Fowl Lake. 4. Weather readings, general terrain, and times of each test were recorded on a data sheet for the nine sound points. Photos were also taken at each point corresponding to the 4 cardinal directions. Equipment Used 1. A Dell AXIM personal data recorder was used to record the sound of a snowmobile running at approximately 5-10 miles per hour. At 50 feet the recording produced a sound level of decibels. Final Environmental Impact Statement C-9 Appendix C

10 2. The data recorder was connected to a Galls Streetthunder bullhorn. Eight C batteries power the bullhorn. 3. A Ski-Doo Skandic 550 produced the recorded sound. 4. Two Ski-Doo Skandic 550 s were used, one on North Fowl Lake and one on Little John Lake. 5. A Kestrel Mobile Weather Station recorded weather readings. 6. An EXTECH HD600 Digital Datalogging Sound Level Meter on a 4 foot tripod recorded the decibel levels on the Royal River. Summary of the Tests 1. On January 28 th six Forest Service personnel attempted to gather data at all nine sounding points. Due to cold weather and dead batteries in the Dell data recorder, only Sound Points one and two were surveyed (see Map C-1). 2. On January 30 th two Forest Service personnel surveyed Sound Points six and seven. Only the ambient sounds of the Royal River and the recording of a snowmobile on the proposed trail were sampled. 3. On February 5 th six Forest Service personnel surveyed eight sound points on the Royal River. These were points three through ten (see Map C-1). Four recordings of decibel levels were conducted at Points 3 and 4. At Points 5 through 10 three recordings for decibel levels were sampled (the snowmobile on Little John was not recorded at these points). Summary of Test Results 1. The highest decibel level recorded for the snowmobile on Little John Lake was at Sound Point 1. It was approximately 55 decibels at 300 meters. 2. The highest decibel level recorded for the snowmobile recording on the proposed snowmobile trail was at Sound Point 7. It was approximately 45 decibels at 400 meters. 3. The highest decibel level recorded for the snowmobile on North Fowl Lake was at Sound Point 10. It was approximately 55 decibels at 200 meters. 4. Ambient decibel level varied between 39 and 41 decibels at most Sound Points. Final Environmental Impact Statement C-10 Appendix C

11 General Thoughts on the Test 1. The Royal River is difficult to snowshoe. Open water and thin ice prevented Forest Service personnel from sampling the entire river, especially the area between points 2 and 3 (see Map C-1). One Forest Service employee broke through the ice on the river near Sound Point There were no human tracks or snowmobile tracks on the entire river. 3. Throughout the tests on February 5 th a road grader could be heard on the Arrowhead Trail, but was not loud enough to be recorded on the Decibel Meter. Snowmobiles on McFarland Lake could also be heard throughout the tests, but were not loud enough to be recorded on the Decibel Meter. 4. Snowmobiles could be heard on the Fowl Lakes throughout the tests, but were not loud enough to be recorded on the Decibel Meter. Sound Recordings Enclosed is a series of sound graphs from each sounding point (see Map C-1). Following is a summation of what we recorded. 1. Point 1 recorded the snowmobile on Little John Lake. The graph spiked at 55 decibels at 300 meters, with ambient decibels at Points 5 and 6 recorded the snowmobile recording from the proposed trail site (refer to Map C-1). Sound Point 5 s maximum decibel was 44.1 at 440 meters, where as the ambient sound was At Sound Point 6, the maximum decibel was 44.8 at 400 meters, with ambient decibels at Point 10 recorded the snowmobile noise on North Fowl Lake. Maximum decibels were 54.3 at 200 meters, with ambient decibels at 39 decibels. Participating U.S. Forest Service Personnel Tom Kaffine Pete Lindgren Heather Fox Rich Kujawa Sue Abrahamsen Ryan Blaisdell Harvey Sobieck Rob Bryers Ike Heruth Final Environmental Impact Statement C-11 Appendix C

12 Map C-1: Sound Test Locations. Final Environmental Impact Statement C-12 Appendix C

13 Photo C-1: Sound point 7 Royal Lake 01/30/2009 Photo C-2: Tom Kaffine at Sound point 7. Sub-Zero Temps. 01/30/2009 Final Environmental Impact Statement C-13 Appendix C

14 Photo C-3: Sound point 8 02/05/2009. Arrow is approximate location of recorded snowmobile sound (proposed trail). Photo C-4: Little John Lake. Area of operation for snowmobile running 15-20mph. 01/28/2009 Final Environmental Impact Statement C-14 Appendix C

15 Photo C-5: North Fowl Lake area of operation for snowmobile 40-50mph. 02/05/2009 Photo C-6: Photo from trail recording broadcast point (proposed trail). Looking south toward Royal River. 02/05/2009 Final Environmental Impact Statement C-15 Appendix C

16 Photo C-7: Royal River looking Northwest from Sound point 5. Notice dark color of ice indicating unsafe ice. Temperatures up to this point have been sustained well below freezing. 01/30/2009 Photo C-8: Royal River looking west toward John Lake. 01/28/2009 Final Environmental Impact Statement C-16 Appendix C

17 Sound Point 1. Background. 01/28/ Decibel spike was caused by squirrel. Average dba: Sound Point 1 Little John snowmobile. 01/28/ Decibel spikes 44dba maximum caused by snowmobile on Little John. Final Environmental Impact Statement C-17 Appendix C

18 Sound Point 1 Trail Recording. 01/28/ Decibel spikes are wind gusts. Recording not audible. Average dba: 40.7 Sound Point 1 North Fowl Lake Snowmobile. 01/28/ Decibel spike is wind gust. Snowmobile is not audible. Average dba: 38.1 Final Environmental Impact Statement C-18 Appendix C

19 Sound Point 2 Background. 01/28/ Running water ambient noise. Max dba: 44.1 Sound Point 2 Little John Snowmobile. 01/28/ Snowmobile not audible. Max dba:44.7 Final Environmental Impact Statement C-19 Appendix C

20 Sound Point 2 Trail Recording. 01/28/ Recording not audible. Max dba: 44.4 Sound Point 2 North Fowl Snowmobile. 01/28/ Snowmobile not audible. Max dba: 44.8 Final Environmental Impact Statement C-20 Appendix C

21 Sound Point 3 Background. 02/05/ Average dba: 39 Sound Point 3 Trail Recording. 02/05/ Volume on recording set to high. Average dba: 41 Final Environmental Impact Statement C-21 Appendix C

22 Sound Point 3 North Fowl Snowmobile. 02/05/ Decibel spikes were wind gusts. Could hear snowmobile but did not register. Average dba: 40.7 Sound Point 4 Background. 02/05/ Average dba: 41.4 Final Environmental Impact Statement C-22 Appendix C

23 Sound Point 4 Little John Snowmobile. 02/05/ Snowmobile audible but did not register. Average dba: 41 Sound Point 4 Trail Recording. 02/05/ Decibel spikes caused by wind gusts. Average dba: 42.4 Final Environmental Impact Statement C-23 Appendix C

24 Sound Point 4 North Fowl Snowmobile. 02/05/ Snowmobile audible but did not register. Decibel spikes are wind gusts. Average dba: 40.1 Sound Point 5 Background. 01/30/ Average dba 37.4 Final Environmental Impact Statement C-24 Appendix C

25 Sound Point 5 Trail Recording. 01/30/ Decibel spike is trail recording. Max. dba: 44.1 Average dba: 40.3 Sound Point 5.1 Background. 02/05/ Large sustained wind caused spikes. Average dba: 45 Final Environmental Impact Statement C-25 Appendix C

26 Sound Point 5.1 Little John. 02/05/ Decibel spikes caused by wind. Could here snowmobile but it did not register. Average dba: 45.7 Sound Point 5.1 Trail Recording. 02/05/ Spikes caused by sustained wind gust. Decibel level for snowmobile no wind was visually recorded as 43dba. Final Environmental Impact Statement C-26 Appendix C

27 Sound Point 5.1 North Fowl Snowmobile. 02/05/ Decibel spikes caused by wind gusts. Could barely hear snowmobile. Average dba: 42.8 Sound Point 6 Background. 01/30/ Average dba: 38.3 Final Environmental Impact Statement C-27 Appendix C

28 Sound Point 6 Trail Recording. 01/30/ Trail recording very clear. Recording spiked at 40.7dba. Average dba: 39.6 Sound Point 6.1 Background. 02/05/ Blocked wind from data logger. Average dba: 39.4 Final Environmental Impact Statement C-28 Appendix C

29 Sound Point 6.1 Trail Recording. 02/05/ Blocked wind from data logger. Peak recording dba Average dba: 42.5 Sound Point 6.1 North Fowl Snowmobile. 02/05/ Could barely hear snowmobile. Average dba: 39.6 Final Environmental Impact Statement C-29 Appendix C

30 Sound Point 7 Background. 02/05/ Average dba: 39 Sound Point 7 Trail Recording. 02/05/ Large spike was caused by a sniffle. Recording audible. Average dba: 41.5 Final Environmental Impact Statement C-30 Appendix C

31 Sound Point 7 North Fowl Snowmobile. 02/05/ Could hear snowmobile but did not register. Max. dba: 39 Sound Point 8 Background. 02/05/ Spike caused by a sniffle. Average dba: 39.1 Final Environmental Impact Statement C-31 Appendix C

32 Sound Point 8 Trail Recording. 02/05/ Could hear recording but did not register. Average dba: Sound Point 8 North Fowl Snowmobile. 02/05/ Could not hear snowmobile. Average dba: 38.9 Final Environmental Impact Statement C-32 Appendix C

33 Sound Point 9 Background. 02/05/ Could hear water in rapids and mechanical noise from McFarland Lake area. Average dba: 40.7 Sound Point 9 Trail Recording. 02/05/ Recording faintly heard but did not register. Average dba: 40.8 Final Environmental Impact Statement C-33 Appendix C

34 Sound Point 9 North Fowl Snowmobile. 02/05/ Could here snowmobile clearly. Average dba: 40.6 Sound Point 10 Background. 02/05/ Decibel spike was caused by a sniffle. Average dba: 37.7 Final Environmental Impact Statement C-34 Appendix C

35 Sound Point 10 Trail Recording. 05/05/ Could barely hear recording. Average dba: 37.8 Sound Point 10 North Fowl Snowmobile. 02/05/ Maximum dba: 54.3 caused by snowmobile. Average dba: 41.5 Final Environmental Impact Statement C-35 Appendix C

36 Royal River Sound Test March 2, 2010 South Fowl Lake Snowmobile Access Project Sound tests were conducted on the Royal River in the Boundary Waters Canoe Area Wilderness on March 2, The purpose was to measure the decibel level in the wilderness of a snowmobile s engine running at 10 mph outside the wilderness. The following is a summary of the methods and equipment used, and a summary of the results. Methodology 1. A recording was made of a snowmobile s engine running at 10mph. The db for the recording was approximately 102 db 1 foot away from the snowmobile s engine. 2. The sound (102db) was projected by a bullhorn at a point on the proposed snowmobile trail nearest the wilderness boundary. 3. The decibel meter was placed on Royal Lake. Ambient noise was recorded. The decibel meter was then moved north away from the bullhorn until the decibel reading was just above (2 decibels higher) than the ambient recording. The meter was left at this spot for the remainder of the test. The GPS point was recorded for the datalogger site so that the distance between the recording and the datalogger could be measured. 4. The bullhorn operator then moved east and west 1000 feet, playing the recording every 200 feet. Results for each test were recorded on the decibel meter. GPS points were recorded at 200 foot intervals to measure the distance between the sound recording and the datalogger. Equipment Used 1. A Trimble Juno SB was used to record the snowmobile engine running at 10mph. 2. The Juno was connected to a Galls Streetthunder bullhorn running on 8 C batteries. 3. A Ski-Doo Skandic 550 produced the recorded sound. 4. An EXTECH HD600 Digital Datalogging Sound Level Meter on a 4 foot tripod recorded the decibel levels on Royal Lake. The datalogger was set to record db levels between 30 and 130 decibels. The C setting was used for the frequency weighting since this setting is recommended by the manufacturer for capturing engine noise. 5. A Kestrel Mobile Weather Station recorded weather readings. Final Environmental Impact Statement C-36 Appendix C

37 Results: Due to operator error, many of the recordings were incorrect. Instead of turning on the recording button, the operator was actually turning off the recording. However, 5 recordings were correct. 1. Ambient noise was recorded at about 33 decibels (good recording). 2. The site of the datalogger was 1562 feet north of the bullhorn on the proposed trail. 3. The decibel level read by the recorder at this point, with the bullhorn running at the closest point on the proposed trail to the Wilderness line was 34.9 (visually recorded). 4. The bullhorn was moved 100 feet west, with the decibel reading at this point at 35 (good recording). 5. The remainder of the recordings were defective due to operator error. However, the operator recorded visually the highest decibel readings for the remainder of points. A. 100 feet east of original bullhorn broadcast point: 34.8 decibels B. An additional 100 feet east: 34.5 decibels C. An additional 200 feet east: 34.1 decibels D. An additional 200 feet east: 34.5 decibels E. An additional 200 feet east: wind gusts ended any recording F. 100 feet west of original bullhorn broadcast point: 35 decibels (good recording) G. An additional 100 feet west: 34.9 decibels H. An additional 200 feet west: 34.3 I. An additional 200 feet west: 34.0 J. An additional 200 feet west: wind gusts ended any recording One additional test was performed. One tester snowshoed down the Royal River (Northeast) until the bullhorn broadcast could no longer be heard. This furthest point was 2,760 feet from the broadcast point. The test period ran from 1030 to Weather The weather was recorded at 1100 hours. The readings were as follows: Temperature: 32 degrees Humidity: 34% Wind: 0-4 mph, variable Additional Information: Snowmobiles were heard on South Fowl Lake, but not picked up by the data recorder. There was no sign of human activity recently or perhaps the entire winter. The Tilbury Trail had not been snowmobiled for perhaps the entire winter. Final Environmental Impact Statement C-37 Appendix C

38 C-3: Photos Displaying Location of Sound Source The photos shown in this appendix were taken from an aircraft flying approximately 4000 feet above sea level, which in this area is roughly 2500 feet above ground level. These photos have been altered in two ways. First was to darken the photo which had the effect of creating better visibility of the snowmobile use. That use is the subject of the photos in trying to display where they are ridden, hence where the sound would originate. The photos can then be correlated with Figure 3-3, Chapter 3 from the analysis to demonstrate where the sounds are projected into the BWCAW. The second alteration was to downsize the photo to properly fit on this page. The photos were not cropped or changed in any other way. These photos were taken March 1, 2006, unaltered copies of the original photos (they are digital photos) are included in the project file. Photo C-9: Shoreline of South Fowl Lake with fresh snowmobile track shown on the lake. The bay on the top middle part of the photo is where Royal River empties into South Fowl Lake. Final Environmental Impact Statement C-38 Appendix C

39 Photo C-10:. Royal Lake with no evidence of snowmobile traffic. South Fowl Lake Snowmobile Access Project Photo C-11: Royal River looking toward John Lake with no evidence of snowmobile traffic. Note the gray ice indicating that it is very thin and unsafe for walking. Final Environmental Impact Statement C-39 Appendix C

40 Photo C-12: The lower left is a cleared helispot, while the center is Little John Lake and the upper is John Lake. Snowmobile tracks are clear on the helispot and circling Little John Lake (outside the BWCAW) but are not seen on John Lake (inside the BWCAW). Photo C-13: The eastern end of McFarland Lake, the bridge where Arrowhead Road turns into McFarland Lake road (to access the cabins on the north side of the lake) and Little John Lake. Snowmobile traffic is clearly seen on both McFarland and Little John. The blackened area under and on both sides of the bride is open water. Final Environmental Impact Statement C-40 Appendix C

41 Photo C-14: On the right is the western edge of McFarland Lake showing the snowmobiles circle the lake. On the left is Pine Lake (in the BWCAW) with no evidence of snowmobile traffic. The blackened area from McFarland to Pine is open water. Final Environmental Impact Statement C-41 Appendix C

42 C-4: Model for Sound Decibel Level Decay Rates through Air Data and formulas for this information in this Appendix is part of a Microsoft excel spreadsheet; it is only represented as a word document for the purposes of this report. The data can be manipulated to test various results for sound levels and distances. The formulas shown on the third page are fixed while the data entry in the red blocks on the first page can be changed. Results are shown both numerically (green block) and graphically with a sample graph shown in Figure C-2 (in Section C-1 of this Appendix). A different graph is produced for each calculated result. 100 Snomobile Sound Level (db) Reference Levels from Sound Assessment 0.01 Is 110 db Car Horn, Snowblower 800 Distance (ft) 100 db Blow-dryer, Diesel Truck Distance (m) 85 db Electric Saver, Lawn Mower I at Distance 80 db Garbage Disposal, Vacuum Sound Level at Distance (db) 70 db Alarm Clock, City Traffic db Normal Conversation * 60 db Dishwasher 50 db Library 40 db Leaves Rustling, Refrigerator 30 db Remote Forest DESCRIPTION Input in Sound Level in Cell A1 * Depends on Distance (60 db at 1 meter) Values of Note: For 100 db At 93 ft from the source, the sound is at conversation level (60db) However, as seen from the Graph (especially if the range is extended), this decay is due to the logarithmic nature of the decibel scale Final Environmental Impact Statement C-42 Appendix C

43 Distance (m) Sound Level (db) Distance (ft) Is Final Environmental Impact Statement C-43 Appendix C

44 Final Environmental Impact Statement C-44 Appendix C

45 Final Environmental Impact Statement C-45 Appendix C

46 Final Environmental Impact Statement C-46 Appendix C

47 Final Environmental Impact Statement C-47 Appendix C

48 Final Environmental Impact Statement C-48 Appendix C

49 Final Environmental Impact Statement C-49 Appendix C

50 Final Environmental Impact Statement C-50 Appendix C

51 Final Environmental Impact Statement C-51 Appendix C

52 This model was developed from college level physics text book (University Physics: with Modern Physics by Young and Freedman). This is a basic sound level decrease through air equation, not accounting for vegetation screening. Final Environmental Impact Statement C-52 Appendix C