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2 fax October 15, 2013 SUBJECT: Noise Assessment for the Herbert Hoover High School Athletic Facilities Upgrade, City of San Diego The Acoustical Site Assessment Herbert Hoover High School Athletic Facilities Upgrade Project San Diego, dated August 16, 2010, conducted by Investigative Science and Engineering, Inc., adequately addressed existing noise conditions at the Project and expected constructionrelated noise impacts, and evaluated expected noise impacts from operations of the completed Project. Subsequently, Ldn Consulting, Inc. (Ldn) reanalyzed the noise impacts based on actual operations of the now-existing facility, and compared them with applicable noise impact thresholds. This report supersedes and replaces only the operational and traffic noise assessment sections in the prior report. SUMMARY Based on the analysis below, the operation of a football game that generates noise sources from the use of a PA system, crowd cheering, and a band would be expected to generate noise exceeding City standards at the nearest residences. It should be noted, however, that the football field and a baseball field have been on the site for many years and the prior activities on the fields likely exceeded the standards. As discussed below, no feasible mitigation measure is identified that would result in a significant noise reduction. Therefore, a significant and unmitigable noise impact is identified for the Project. 10/15/ Supplemental Hoover HS Noise Findings

3 PROJECT DESCRIPTION As part of the Project, bleachers were refurbished, replaced or added. For the home side stadium bleachers, there was a net loss of 1,394 seats (previous seating of 4,190 seats was reduced to 2,796 seats, including 30 wheelchair spaces). On the visitor stadium side bleachers, there was a net loss of 271 seats (previous seating of 1,445 seats was reduced to 1,174 seats, including 14 wheelchair spaces). The following describes the recent improvements that were completed to upgrade the athletic facility: Stadium Upgrades: Replaced existing home side bleachers; Replaced existing visitor side bleachers and installed a concrete masonry screen wall at bleachers and ramps; Replaced the existing press box with new press box and elevator for wheelchair access; Constructed a new 3,436 square foot athletic services building with new Breitbard Stadium sign; Installed new lighting for the football field (two 99 foot light standards on south side of football field and two 87 foot light standards on north side of football field). The field lighting is focused and directed at the field area during school events, including sporting events (i.e., football, soccer, track) that occur after dusk. The facility is cleaned and the field lights are extinguished (approximately at 10:00 p.m.); Installed an upgraded public announcement (PA system); Installed a new ornamental steel perimeter fence surrounding the football field; Installed stand-up snack tables; Salvaged and re-installed constructed concrete base and plaque Arnold Margulis Memorial Track ; and Constructed a concrete masonry wall (268 feet long, 11 feet high, with 12-foot return at each end) on the northern side of visitor bleachers (parallel to Monroe Avenue), which serves to visually screen the bleachers from the surrounding neighborhood. Note: Access to the football field would only be available from the internal portion of the school campus through the eastern portion of the football field at the new athletic services building. 10/15/ Supplemental Hoover HS Noise Findings

4 Softball Field Upgrades: Replaced the existing tennis courts with a new softball field; Installed a new softball scoreboard; Constructed new accessible dugouts; Constructed new softball batting cages; and, Installed a new chain link perimeter fence with green widescreen. Baseball Field Upgrades: The existing bleachers (162 seats) were replaced to accommodate 356 seats including four wheelchair spaces; Replaced existing dugouts with new accessible dugouts; Constructed a new 15-foot wall with sign for Ted Williams Field ; Installed serpentine seating wall; Installed a new baseball scoreboard; Constructed a new maintenance equipment storage building; and, Installed a new chain link perimeter fence with green widescreen. Overall School Campus: Repaired existing city-owned sidewalks that surround the school for ADA compliance; and, Installed new landscaping. The Project site is shown in Figure 1. 10/15/ Supplemental Hoover HS Noise Findings

5 Figure 1: Project Site Layout 10/15/ Supplemental Hoover HS Noise Findings

6 ACOUSTICAL FUNDAMENTALS The following are brief definitions of terminology associated with noise assessments: Sound Pressure Level (SPL): a ratio of one sound pressure to a reference pressure (Lref) of 20 μpa. Because of the dynamic range of the human ear, the ratio is calculated logarithmically by 20 log (L/Lref). A-weighted Sound Pressure Level (dba): Some frequencies of noise are more noticeable than others. To compensate for this fact, different sound frequencies are weighted more. Minimum Sound Level (Lmin): Minimum SPL or the lowest SPL measured over the time interval using the A-weighted network and slow time weighting. Maximum Sound Level (Lmax): Maximum SPL or the highest SPL measured over the time interval the A-weighted network and slow time weighting. Equivalent sound level (Leq): the true equivalent sound level measured over the run time. Leq is the A-weighted steady sound level that contains the same total acoustical energy as the actual fluctuating sound level. Community Noise Exposure Level (CNEL): The accumulated exposure to sound measured in a 24-hour sampling interval and artificially boosted during certain hours. For CNEL, samples taken between 7 pm and 10 pm are boosted by 5 db; samples taken between 10 pm and 7 am are boosted by 10 db. Noise is defined as unwanted or annoying sound which interferes with or disrupts normal activities. Exposure to high noise levels has been demonstrated to cause hearing loss. The individual human response to environmental noise is based on the sensitivity of that individual, the type of noise that occurs and when the noise occurs. Sound is measured on a logarithmic scale consisting of sound pressure levels known as a decibel (db). The sounds heard by humans typically do not consist of a single frequency but of a broadband of frequencies having different sound pressure levels. The method for evaluating all the frequencies of the sound is to apply an A-weighting to reflect how the human ear responds to the different sound levels at different frequencies. The A-weighted sound level adequately describes the instantaneous noise whereas the equivalent sound level depicted as Leq represents a steady sound level containing the same total acoustical energy as the actual fluctuating sound level over a given time interval. 10/15/ Supplemental Hoover HS Noise Findings

7 The Community Noise Equivalent Level (CNEL) is the 24 hour A-weighted average for sound, with corrections for evening and nighttime hours. The corrections require an addition of 5 decibels to sound levels in the evening hours between 7 p.m. and 10 p.m. and an addition of 10 decibels to sound levels at nighttime hours between 10 p.m. and 7 a.m. These additions are made to account for the increased sensitivity during the evening and nighttime hours when sound appears louder. A vehicle s noise level comes from a combination of the noise produced by the engine, exhaust and tires. The cumulative traffic noise levels along a roadway segment are based on three primary factors: the amount of traffic, the travel speed of the traffic, and the vehicle mix ratio or number of medium and heavy trucks. The intensity of traffic noise is increased by higher traffic volumes, greater speeds and increased number of trucks. Because mobile/traffic noise levels are calculated on a logarithmic scale, a doubling of the traffic noise or acoustical energy results in a noise level increase of 3 dba. Therefore the doubling of the traffic volume, without changing the vehicle speeds or mix ratio, results in a noise increase of 3 dba. Mobile noise levels radiate in an almost oblique fashion from the source and drop off at a rate of 3 dba for each doubling of distance under hard site conditions and at a rate of 4.5 dba for soft site conditions. Hard site conditions consist of concrete, asphalt and hard pack dirt while soft site conditions exist in areas having slight grade changes, landscaped areas and vegetation. On the other hand, noises from fixed/point sources radiate outward uniformly as they travel away from the source. Their sound levels attenuate or drop off at a rate of 6 dba for each doubling of distance. The most effective noise reduction methods consist of controlling the noise at the source, blocking the noise transmission with barriers or relocating the receiver. Any or all of these methods may be required to reduce noise levels to an acceptable level. APPLICABLE STANDARDS The generation of noise from certain types of land uses could cause potential land use incompatibility. A project which would generate noise levels at the property line which exceed Section of the City s Municipal Code is considered to have a potentially significant impact, as identified in Table 1. Section of the Noise Ordinance sets a more restrictive operational exterior noise limit for residential uses of 50 dba Leq for daytime hours of 7 a.m. to 7 p.m. and 45 dba Leq during the evening hours of 7 p.m. to 7 a.m. Project components will typically operate during 10/15/ Supplemental Hoover HS Noise Findings

8 the daytime and evening hours. Therefore the most conservative approach is to apply the 45 dba Leq evening standard at the property lines. Table 1: Sound Level Limits in Decibels (dba) Source: City of San Diego Noise Ordinance Section The City standards do not necessarily apply to the San Diego Unified School District since the school district is a separate agency. However, this analysis uses the City standards as thresholds to determine significance. OPERATIONAL LINE NOISE LEVELS Events conducted within the athletic stadium that were possible only during the daylight hours or with temporary lights would be able to occur in the evening with the proposed new field lighting. These events include football, soccer, and track and field. The stadium lighting will be utilized for approximately 15 evening events per year. The highest use of the stadium would be from an evening football game. It is anticipated that of the approximately 15 evening events, approximately six (6) of those events would be evening football games. 10/15/ Supplemental Hoover HS Noise Findings

9 Noise measurements of a home football game were conducted on September 6, 2013 between the hours of 6 pm and 9 pm at the site. The measurements were taken using Larson-Davis Spark 706 Type 2 precision sound level meters, programmed, in "slow" mode, to record noise levels in "A" weighted form. The sound level meters and microphones were mounted five feet above the ground and equipped with a windscreen during all measurements. The sound level meters were calibrated before and after the monitoring using a Larson-Davis calibrator, Model CAL 150. The noise levels during the measurements included people arriving to the game, crowds cheering, the high school band playing between plays and during intermissions along with the public announcements (PA) system and then people leaving after the game. The primary noise levels consisted of crowds cheering, the high school band playing between plays and during intermissions along with the public announcements (PA) system. The results of the noise level measurements are presented in Table 2 on the following page. The noise levels measured during the football game were found to be between dba Leq and were above the City s property line threshold by roughly 5-20 dba during the entire football game as can be seen graphically in Figure 2 below. The noise monitoring locations are provided in Figure 3 on the following page. The noise measurement data is provided as an attachment to this report. Attendance at the football game during the noise measurements was 532 persons based on ticket sales, plus 40 high school band members. Based on the Project s traffic study, it is anticipated that attendance during normal (non-homecoming games) could be 750 people and during the homecoming game as many as 1,340 people would attend (Source: Herbert Hoover High School Completed Athletic Facilities Upgrades San Diego Unified School District, LOS Engineering dated October 2013). Therefore, noise levels from a normal (non-homecoming game) and noise levels from the Homecoming Game would be higher than what was measured. It is anticipated that the noise levels at nearby residences, during a normal game with 750 spectators, could increase 1-3 decibels and an increase of 3-6 decibels could occur during a Homecoming Game due to the additional attendance and onsite activities (i.e., halftime events, etc.). The noise levels exceeding the City s standards would occur only periodically as there would be a limited number of events at the proposed stadium (approximately 15 per year). Further, noise levels would be intermittent and variable depending on the size of the crowd, the amount the band plays and the number of PA announcements. 10/15/ Supplemental Hoover HS Noise Findings

10 Table 2: Measured Noise Levels (during the entire game) Location Primary Noise Source Date and Time Noise Levels (dba Leq) M M2 Football Game Activities 58.5 September 6, 2013 M3 (combination of PA System, Band :00-9:00 p.m. playing and Crowd cheering) M M Source: Ldn Consulting 9/6/13 at Hoover High School Football Game. Figure 2: Noise Monitoring Results 10/15/ Supplemental Hoover HS Noise Findings

11 Figure 3: Noise Monitoring Locations Finally, the project has incorporated design features to help reduce noise levels. As part of the PA system, the District shall ensure that the PA system is either directional in nature (i.e., the ability to direct the majority of the sound away from the property line); install a 4-channel amplifier system; or, have the ability to be adjusted to a minimum of 10.0 db during evening hours to reduce noise impacts to offsite sensitive receptor areas during these quieter hours. The speakers installed on the Stadium Lighting Poles have adjustable coverage patterns and have been adjusted to fit the minimal area of coverage to maximize the sound levels for the audience and minimize the bleed over noise into the residential areas. The speakers are directional and have shrouds that channel noise output away from offsite receptors. 10/15/ Supplemental Hoover HS Noise Findings

12 The visitor seating, closest to the residences, has been constructed with a solid wall on the back of the bleachers to minimize noise. TRAFFIC RELATED NOISE Traffic related noise level changes greater than 3 dba are often identified as audible and are considered an acceptable means of determining a potentially significant increase. In the range of 1 to 3 dba, residents who are very sensitive to noise may perceive a slight change, while changes less than 1 dba are rarely discernible. Therefore, the level at which changes in community noise levels become discernible is likely greater than 1 dba and an increase of 3 dba appears to be appropriate for most people. For the purposes for this analysis, a traffic noise impact would be considered significant if the project increases noise levels for a noise sensitive land use by 3 dba CNEL AND if the project increases noise levels above an unacceptable noise level per the City s Noise Compatibility Guidelines (typically 65 dba CNEL for residential uses). Typically it requires a project to double (or add 100%) to the traffic volumes to have an increase of 3 dba CNEL. Along unclassified roadways with speed limits of MPH (residential streets), it would require a peak hour volume of 400 vehicle trips or more to increase the noise levels above the City s acceptable residential threshold of 65 dba CNEL at a distance of 25 feet from the centerline of the roadway and 800 peak hour trips to reach 65 dba CNEL at 50 feet from the centerline of the roadway. To determine if off-site noise level increases associated with the traffic from a football game would create noise impacts, the traffic volumes for the existing conditions were compared with the traffic volume increase from the proposed project during a Homecoming Game. The only roadway segments that have a peak hour volume above 400 are along El Cajon Boulevard and the Project s related traffic will not cause a doubling of traffic resulting in a 3 decibel increase (Source: Herbert Hoover High School Completed Athletic Facilities Upgrades San Diego Unified School District, LOS Engineering dated October 2013). Based on the project s traffic assessment several of the roadways adjacent to the school site will experience a doubling of traffic during the Homecoming Game. The doubling of the peak hour volumes could increase the noise levels 3 dba or more but none of the segments have a peak hour (existing plus project event) above 400 trips and therefore would not exceed the City s 65 dba CNEL threshold. The highest increases from a Homecoming Game occur along 46 th Street and Monroe Avenue. Along 46 th Street a Homecoming Game adds 174 trips to an existing peak hour volume of 85 trips which equates to 259 peak hour trips. Along Monroe Avenue the existing peak was found to be 132 trips and a Homecoming Game would add /15/ Supplemental Hoover HS Noise Findings

13 trips but only equating to 271 total trips. These volumes would result in a noise level of approximately 63 dba CNEL at 25 feet for the centerline. It should be noted: the existing peak hour trips and project related trips do not occur at the same time and the overall traffic volumes could be lower which would result in lower noise levels. Therefore, the project related traffic would not exceed the City s thresholds and no impacts are anticipated. CONCLUSIONS The installed features have helped reduce noise levels at nearby sensitive receptors to the degree feasible. A mitigation measure to construct a solid wall that extends from the ground up to a point 6 feet above the top row of the bleachers that extends around the perimeter of the stadium was analyzed. The wall would need to be at least 30-feet tall and the PA speakers located on the light poles, which are currently at a height of 45 feet, would need to be lowered to 25 feet on the light poles. As depicted on Figure 4, the wall would be constructed along the entire north, east, and west perimeter of the stadium. Figure 4: Noise Barrier Location 10/15/ Supplemental Hoover HS Noise Findings

14 The primary purpose of the barrier is to preclude residential receptors from a direct line-ofsight to the top of the bleachers and the PA system. The wall barrier would reduce the noise levels from the stadium by approximately 5-10 dba. The wall barrier would not be effective at receptors with views of the bleachers or views of field activity. The noise attenuation provided by the noise barrier behind the bleachers is not sufficient to reduce the noise impact during football games to a less than significant level; football games would continue to substantially increase hourly average noise levels, exceeding the City's noise standards by up to dba Leq as compared to the proposed project which exceeds the City s noise standards by 5-20 dba Leq. Therefore, this method cannot achieve the noise reduction required to meet the hourly average noise threshold and reduce the impact from football games to a less than significant level. Further, based on some preliminary costs estimates, the wall barrier would cost approximately $1.5 Million and in order for the District to be able to maintain the existing emergency access gates, solid gates would need to be installed along the wall. Due to the high cost to construct the wall and because the wall would only result in a 5-10 dba decrease and would not reduce the impact to a level less than significant. This mitigation measure has been determined to be infeasible. Another option to reduce noise would be to lower the elevation of the stadium. Lowering the elevation of the stadium approximately 25 feet below the current grade would place the top of the visitor bleachers at the existing elevation of the field, and the playing field would be approximately 25 feet lower in a "bowl". The PA system would also need to be lowered to current grade elevations. Calculations were made to determine the noise reduction provided by depressing the field below grade. Because of the proximity of residential receptors, and the height of the average noise source, assumed to be 15 feet above the field and track base elevation, depressing the field 25 feet could break the line-of-sight from the bleachers and reduce noise levels by approximately 5 dba. The noise levels during a football game would exceed the City's noise standards by up to 15 dba Leq. This method cannot achieve the noise reduction required to meet the hourly average noise threshold and reduce the impact from football games to a less than significant level. Depressing the stadium 25 feet, in combination with the construction of an 8-foot noise barrier around the perimeter of the stadium was also analyzed. The lowering of the stadium and the 8-foot noise barrier should achieve approximately 10 dba of noise reduction. However, this additional 5 dba of noise reduction would still not reduce football event noise levels to a less than significant level. The mitigated worst-hour noise levels would continue to result in a substantial increase in noise, exceeding the City s noise standards. In fact, the stadium would need to be lowered at least 50 feet and have a perimeter wall installed to fully mitigate the noise levels below the City s noise standards. 10/15/ Supplemental Hoover HS Noise Findings

15 Furthermore, digging the field below grade would require a substantial amount soil to be excavated and trucked to a location that would accept the soil. In addition, to build a stadium below grade would require a much larger footprint than the current available footprint on the site for the stadium. Additional land is not available for the District because the stadium is surrounded by existing classroom buildings and residential units. Lastly, a stadium below grade would require additional ADA upgrades to ensure proper conveyance, likely mechanical conveyance, in order to make the facility ADA compliant. Based on these factors this mitigation option is impracticable and not a feasible mitigation measure. The final option would be to enclose the stadium with walls and a roof, similar to a dome. The enclosure should reduce the noise levels by 20 dba and the events would comply with the City noise standards. However, the cost to construct a dome would be several times more expensive than installing the 30 foot wall. Due to the high cost to construct a dome, this mitigation measure has been determined to be infeasible. Though events would occur only periodically, they would be expected to generate noise exceeding City standards at the nearest residences. It should be noted, however, that the football field and a baseball field have been on the site for many years and the prior activities on the fields likely exceeded the standards. The project will not increase noise levels along the roadways by 3 dba CNEL AND increase the noise levels above the City s Noise Compatibility Guidelines of 65 dba CNEL for residential uses. Therefore, no traffic related noise impacts are anticipated. Sincerely, Ldn Consulting, Inc. Jeremy Louden, Principal Attachment: Noise Measurement Data 9/6/13 10/15/ Supplemental Hoover HS Noise Findings

16 General Information Serial Number Model 706 User Job Description Location Start Time Friday, 6 September :07:05 Stop Time Friday, 6 September :23:05 Run Time 03:16:00 Sample Interval 60 Sec. Note Results Dose 1 Dose 2 Dose 3 Dose 4 Dose % Projected Dose % Leq dba TWA dba TWA (8) dba Lmax dba Lpeak (max) db Lmin dba Lep (8) dba SE Pa²hr Overload? Yes Statistics L dba L dba L dba L dba L dba Settings Exchange Rate Threshold dba Criterion Level dba Criterion Duration hours RMS Weight A Weighting Peak Weight Unweighted Detector Slow Gain 30 db LPeak (max) is instantaneous and unweighted and does not account for the response of the human hear.

17 General Information Serial Number Model 706 User Job Description Location Start Time Friday, 6 September :45:38 Stop Time Friday, 6 September :20:38 Run Time 03:35:00 Sample Interval 60 Sec. Note Results Dose 1 Dose 2 Dose 3 Dose 4 Dose % Projected Dose % Leq dba TWA dba TWA (8) dba Lmax dba Lpeak (max) db Lmin dba Lep (8) dba SE Pa²hr Overload? Yes Statistics L dba L dba L dba L dba L dba Settings Exchange Rate Threshold dba Criterion Level dba Criterion Duration hours RMS Weight A Weighting Peak Weight Unweighted Detector Slow Gain 30 db LPeak (max) is instantaneous and unweighted and does not account for the response of the human hear.

18 General Information Serial Number Model 706RC User Job Description Location Start Time Friday, 6 September :21:34 Stop Time Friday, 6 September :04:34 Run Time 03:43:00 Sample Interval 60 Sec. Note Results Dose 1 Dose 2 Dose 3 Dose 4 Dose % Projected Dose % Leq dba TWA dba TWA (8) dba Lmax dba Lpeak (max) db Lmin dba Lep (8) dba SE Pa²hr Overload? No Statistics L dba L dba L dba L dba L dba Settings Exchange Rate Threshold dba Criterion Level dba Criterion Duration hours RMS Weight A Weighting Peak Weight Unweighted Detector Slow Gain 30 db LPeak (max) is instantaneous and unweighted and does not account for the response of the human hear.

19 General Information Serial Number Model 706 User Job Description Location Start Time Friday, 6 September :18:11 Stop Time Friday, 6 September :09:11 Run Time 02:51:00 Sample Interval 60 Sec. Note Results Dose 1 Dose 2 Dose 3 Dose 4 Dose % Projected Dose % Leq dba TWA dba TWA (8) dba Lmax dba Lpeak (max) db Lmin dba Lep (8) dba SE Pa²hr Overload? No Statistics L dba L dba L dba L dba L dba Settings Exchange Rate Threshold dba Criterion Level dba Criterion Duration hours RMS Weight A Weighting Peak Weight Unweighted Detector Slow Gain 30 db LPeak (max) is instantaneous and unweighted and does not account for the response of the human hear.

20 General Information Serial Number Model 706 User Job Description Location Start Time Friday, 6 September :28:11 Stop Time Friday, 6 September :14:11 Run Time 03:46:00 Sample Interval 60 Sec. Note Results Dose 1 Dose 2 Dose 3 Dose 4 Dose % Projected Dose % Leq dba TWA dba TWA (8) dba Lmax dba Lpeak (max) db Lmin dba Lep (8) dba SE Pa²hr Overload? Yes Statistics L dba L dba L dba L dba L dba Settings Exchange Rate Threshold dba Criterion Level dba Criterion Duration hours RMS Weight A Weighting Peak Weight Unweighted Detector Slow Gain 30 db LPeak (max) is instantaneous and unweighted and does not account for the response of the human hear.