Division 7 Community Outreach Division 7 Community Outreach

Soundwall Project

Ramon E. Nugent, P.E.

Acentech, Inc.Acentech, Inc.

Carl RipaldiCarl Ripaldi

Los Angeles County Metropolitan Transit Authority

IntroductionIntroduction

• Bus Depot Overview• Bus Depot Overview

• Community Complaint History

• Previous Actions Taken by Metro• Previous Actions Taken by Metro

• Definition of Problem

• Analysis• Analysis

• Recommendations

• Current Situation• Current Situation

Metro Division 7 Bus Depot – Looking SEMetro Division 7 Bus Depot – Looking SE

Community ComplaintsCommunity Complaints

• Complaints from residences over several years• Complaints from residences over several years

• Residents for Quality of Life action group

• Issues:• Issues:

– Bus idling

– Back-up alarms

– Yard sweepers

– Yard loudspeaker announcements

– Maintenance operations– Maintenance operations

– Vibration

Metro Noise Control ProcessMetro Noise Control Process

1. Metro installed an 8 ft block 1. Metro installed an 8 ft block

wall

Complaints Continued

2. Metro added a 4 ft extension of

plastic fencingplastic fencing

Complaints Continued

3. Metro hired Acentech

Definition of ProblemDefinition of Problem

• Interview Div 7 Operations• Interview Div 7 Operations

• Observe Div 7 bus operations

• Interview residents• Interview residents

• Develop hypothesis of sources of complaints

• Measurement program• Measurement program

– Noise

– Vibration– Vibration

• Analyze data

Definition of ProblemDefinition of Problem

• 240 buses at Div. 7• 240 buses at Div. 7

• 200 buses “roll-out” - 3:30 a.m. and 7:10 a.m.

• Six to twelve buses idling in the yard• Six to twelve buses idling in the yard

• 4 a.m. and 6:00 a.m., eight late-night buses

& 92 “Trippers,” return to the yard& 92 “Trippers,” return to the yard

• Returning buses stop at the base of the ramp

before proceeding south to parking rowbefore proceeding south to parking row

Metro Division 7 Bus DepotMetro Division 7 Bus Depot

Hu

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Dri

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Definition of Problem

Location d1 d2 d3 h1 h2 h3 h4Location d1 d2 d3 h1 h2 h3 h4

1 56 8 8 12 15 6 15

2 30 10 2 12 15 5 152 30 10 2 12 15 5 15

Definition of ProblemDefinition of Problem

Analysis – Field DataAnalysis – Field Data

95

100

L1@ Div 7

L10@ Div 7

Leq@ Div 7

85

90

No

ise L

evel,

dB

A

Leq@ Div 7

L1@ 825

L10@ 825

Leq@ 825

L1@ 835

Bus

Roll-out

Bus

Roll-out

70

75

80

No

ise L

evel,

dB

A L1@ 835

L10@ 835

Leq@ 835

60

65

70

No

ise L

evel,

dB

A

50

55

13

:

15

:

17

:

19

:

21

:

23

:

1:

3:

5:

7:

9:

11

:

13

:

15

:

17

:

19

:

21

:

23

:

1:

3:

5:

7:

9:

11

:

13

:

Hour

Analysis – Field DataAnalysis – Field Data

• Noise levels at residences and at Div 7correlate• Noise levels at residences and at Div 7correlate

• Noisiest periods

– 9 a.m. to 11 a.m. – 9 a.m. to 11 a.m.

– 7 p.m. to 9 p.m. (19:00 to 21:00)

• Highest noise does not correlate with bus roll out• Highest noise does not correlate with bus roll out

• Highest noise occurs when buses return

• Ldn = 62 to 63 dBA• Ldn = 62 to 63 dBA

Analysis - Returning BusesAnalysis - Returning Buses

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Analysis - Bus Spectra

25 Hz 50 Hz75

8014:

15:

16:

17:

125 Hz

65

70

17:

18:

19:

20:

21:

22:

23:

55

60

Le

q, d

BF

23:

0:

1:

2:

3:

4:

45

50

4:

5:

6:

7:

8:

9:

10:

35

40

12

.5 20

31

.5 50

80

12

5

20

0

31

5

50

0

80

0

12

50

20

00

31

50

50

00

80

00

Le

q, d

BA

10:

11:

12:

13:

Le

q, d

BA

1/3-Octave Band, Hz

Analysis: Wall – vs – Bus HeightsAnalysis: Wall – vs – Bus Heights

Wall Dimensions Engine Exhaust Height

11.5 ft

8 ft

12 ft

8 ft

ConclusionsConclusions

• Residential noise correlated with bus yard activities• Residential noise correlated with bus yard activities

• 1st story Ldn’s were between 60 dBA and 65 dBA

• 2nd story Ldns were about 2.5 dB higher• 2nd story Ldns were about 2.5 dB higher

• Existing wall provided 11 to 12 dB reduction

• Needed 4 decibel improvement• Needed 4 decibel improvement

• Noise problem was in the 125 Hz octave band

• Wall TL at low frequencies >22 dB• Wall TL at low frequencies >22 dB

RecommendationsRecommendations

• 16-ft wall• 16-ft wall

• Surface density of at least a 4” solid CMU

• Rated TL of at least 22 dB at 125 Hz 1/3-Octave • Rated TL of at least 22 dB at 125 Hz 1/3-Octave

Band

• Minimize backup alarms during early morning hours• Minimize backup alarms during early morning hours

– Bus parking

– Forklifts– Forklifts

– Maintenance vehicles

Current SituationCurrent Situation

• Built 16-ft+ wall built• Built 16-ft+ wall built

• No noise complaints

• Residences and • Residences and

Metro are Happy

Questions