division 7 community outreach soundwall project€¦ · division 7 community outreach soundwall...
TRANSCRIPT
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
ntl
ey
Dri
ve
Hu
ntl
ey
Dri
ve
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
Hu
ntl
ey
Dri
ve
Hu
ntl
ey
Dri
ve
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