Traffic Noise AssessmentCITY OF CHANHASSEN
RECEIVED
AUG 0 2 2013
CHANHASSEN PLANNING DEPT
Camden Ridge
Chanhassen, Minnesota
TRAFFIC NOISE ASSESSMENT
Prepared for
Pioneer Engineering.
by
David Braslau Associates, Inc.
6603 Queen Avenue S. Suite N
Richfield, MN 55423
Tel: 612 - 331 -4571
Fax: 612-331-4572
Eml: david @braslau.com
Dr. David Braslau, President
2 August 2013
Camden Ridge Traffic Noise Assessment
Table of Contents
1.0
INTRODUCTION .............................................................................. ............................... 1
1.1.
Objectives of this Noise Assessment ............................................... ...............................
1
1.2.
Site Location and Layout ................................................................. ...............................
1
1.3.
Minnesota Noise Standards .............................................................. ...............................
1
1.4.
Report Components .......................................................................... ...............................
4
2.0
METHODOLOGY FOR ANALYZING HIGHWAY NOISE ....... ...............................
5
2.1.
Noise Modeling Assumptions .......................................................... ...............................
5
3.0
TRAFFIC NOISE LEVELS .............................................................. ............................... 7
3.1.
Predicted Noise Levels ..................................................................... ...............................
7
3.2.
Compliance with State Standards for the 6 -7 AM (nighttime) Period ............................
9
3.3.
Construction needed to provide an Exterior- Interior Noise Reduction of 30 dBA.......
10
4.0
SUMMARY OF FINDINGS .............................................................. .............................11
David Braslau Associates, Inc.
Camden Ridge Traffic Noise Assessment
List of Figures
Figure1.1 Site Location ........................................................................... ............................... 2
Figure 1.2 Site Layout and Grading Pl an ............................................... ............................... 3
Figure 2.1 Location of Receptor Sites and Proposed Berm and Noise Wall ...................... 6
List of Tables
Table 1.1 Minnesota State Noise Standards for Residential Land Uses (NAC -1) ........... 1
Table 3.1 Predicted L10 for the PM Peak Hour .................................. ............................... 7
Table 3.2 Predicted L10 for the 6 -7 AM Hour ..................................... ............................... 8
Table 33 6 -7 AM Level s relative to the NAC -2 Standards .............. ............................... 10
David Braslau Associates, Inc.
Camden Ridge Traffic Noise Assessment
1.0 INTRODUCTION
1.1. Objectives of this Noise Assessment
This Noise Assessment evaluates the potential impacts of noise from Trunk Highway 212 on the
proposed Camden Ridge residential development in Chanhassen, Minnesota.
Projected traffic noise levels from TH 212 are compared with the Minnesota daytime and
nighttime noise standards to determine the potential for noise impacts and effectiveness of the
proposed noise wall on top of the existing berms. The exterior- interior noise attenuation
provided by the proposed building construction is assumed for typical construction in Minnesota
and compared with the exemption provisions contained in the Minnesota rules.
1.2. Site Location and Layout
Location of the Camden Ridge development within the City of Chanhassen is shown in
Figure 1.1. The development and grading plan is shown in Figure 1.2. Noise impacts have
been evaluated for receptors at the ground floor and upper floor levels.
1.3. Minnesota Noise Standards
The Minnesota State Noise Standards for residential land uses are presented in Table 1.1.
Residential land uses are included in the NAC -1 (Noise Area Classification -1) under Minnesota
Rule 7030.0040.
Table 1.1 Minnesota State Noise Standards for Residential Land Uses (NAC -1)
L10 is the level exceeded 10% or 6 minutes of an hour. L50 is the level exceeded 50% or 30
minutes of an hour. The L101evel is used as the primary indicator of traffic noise impact since it
accurately reflects the potential impact of traffic.
David Braslau Associates, Inc, Page 1
Da 'me (7:00 am to 10:00 m
Nighttime (10:00 pm to 7:00 am
L10
65 dBA
55 dBA
L50
60 dBA
50 dBA
L10 is the level exceeded 10% or 6 minutes of an hour. L50 is the level exceeded 50% or 30
minutes of an hour. The L101evel is used as the primary indicator of traffic noise impact since it
accurately reflects the potential impact of traffic.
David Braslau Associates, Inc, Page 1
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Camden Ridge Traffic Noise Assessment
1.4. Report Components
Section 2.0 of the report describes the methodology and assumptions used for analyzing traffic
noise.
Section 3.0 of the report addresses projected traffic noise and compliance with state noise
standards.
Section 4.0 presents a summary of findings.
David Braslau Associates, Inc. Page
Camden Ridge Traffic Noise Assessment
2.0 METHODOLOGY FOR ANALYZING HIGHWAY NOISE
Noise levels from TH 212 have been predicted using the MinnNoise highway noise model upon
MnDOT traffic counts on TH 212. Noise levels are evaluated at receptors facing the highway at
each of the proposed lots 5 feet above ground level where outdoor activity can be expected and
also at the upper floors of homes with living and sleeping rooms.
Predicted traffic noise levels are compared with the Minnesota state noise standards to determine
compliance with the standards.
2.1. Noise Modeling Assumptions
Model geometry was based upon the grading plan with adjacent highway layout and elevations
shown on Figure 2.1. Vehicle mix and volumes were taken from the MnDOT MinnNoise
model input for TH 212 just east of the project and adjusted based upon the 2012 volume of
41,500 vehicles per day.
An 8 foot high noise wall on a berm up to 4 feet in height, depending upon location, is proposed
along the entire property fronting TH 212 as shown on Figure 2.1.
Noise receptors have been assumed 5 feet above ground level and at the upper floors of the lots
closest to TH 212.. Some limited shielding of noise is assumed to be provided by homes.
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Camden Ridge Traffic Noise Assessment
3.0 TRAFFIC NOISE LEVELS
3.1. Predicted Noise Levels
Predicted daytime L10 noise levels at ground level receptors (5 feet above ground elevation) and the
upper floor at each of the receptor sites are shown in Table 3.1. The last two columns show the
predicted L10 level relative to the daytime standard of 65 dBA. All levels are expressed in dBA (A-
weighted decibels). Location of the receptor sites is shown on Figure 3.1.
Table 3.1 Predicted L10 for the PM Peak Hour
It can be seen from the table that all of the outdoor ground floor receptors are predicted to be below the
daytime noise standard. Levels at the upper floors upper floor levels are generally several dBA above the
daytime standard but are not intended for outdoor uses. With appropriate home construction required for
compliance with the nighttime standard (see discussion in Section 3.2, the applicable L10 standard will
be 70 dBA, so that these homes will be in compliance with the state noise standards.
David Braslau Associates, Inc. Page 7
L10 PM Period
Re Day Standard
Receptor
Ground Fir
Upper Fir
Ground Fir
Upper Flr
LOT1 -3
62.9
64.4
-2.1
-0.6
LOT1 -4
64.2
66.3
-0.8
1.3
LOT1 -5
63.4
68.6
-1.6
3.6
LOT2 -15/16
62.8
67.8
-2.2
2.8
LOT2 -13/14
1 63.2
67.8
-1.8
2.S
LOT2 -11/12
63.2
67.4
-1.8
2.4
LOT2 -9/10
62.4
66.4
-2.6
1.4
LOT2 -7/8
61.2
65.6
-3.8
0.6
LOT2 -5/6
62.0
63.9
-3.0
-1.1
It can be seen from the table that all of the outdoor ground floor receptors are predicted to be below the
daytime noise standard. Levels at the upper floors upper floor levels are generally several dBA above the
daytime standard but are not intended for outdoor uses. With appropriate home construction required for
compliance with the nighttime standard (see discussion in Section 3.2, the applicable L10 standard will
be 70 dBA, so that these homes will be in compliance with the state noise standards.
David Braslau Associates, Inc. Page 7
Camden Ridge Traffic Noise Assessment
Sound levels have also been estimated for the 6 -7 AM period assuming 60% of the PM peak traffic
which is a typical value for this important commuting hour.
These levels are presented in Table 3.2. The last column shows the predicted L101evel relative to the
nighttime standard of 55 dBA. All levels are expressed in dBA (A- weighted decibels).
Table 3.2 Predicted L10 for the 6 -7 AM Hour
It can be seen that the predicted 6 -7 AM L10 levels exceed the nighttime level by as much as 12 dBA on
the upper floor. However, exceptions to the Minnesota rules permit a higher L10 standard or limit to be
applied if the land use meets certain conditions. These are addressed below in Section 3.2.
David Braslau Associates, Inc. Page 8
L10 6- 7 AM
Re Night Standard
Receptor
Ground Fir
Upper Fir
Ground Fir
Upper Fir
LOT1 -3
61
62
6
7
LOT1 -4
62
64
7
9
LOT1 -5
61
67
6
12
LOT2 -15/16
61
66
6
11
LOT2 -13/14
1 61
66
1 6
11
LOT2 -11/12
61
65
6
10
LOT2 -9/10
60
64
5
9
LOT2 -7/8
59
1
64
4
9
LOT2 -5/6
60
62
5
7
It can be seen that the predicted 6 -7 AM L10 levels exceed the nighttime level by as much as 12 dBA on
the upper floor. However, exceptions to the Minnesota rules permit a higher L10 standard or limit to be
applied if the land use meets certain conditions. These are addressed below in Section 3.2.
David Braslau Associates, Inc. Page 8
Camden Ridge Traffic Noise Assessment
3.2. Compliance with State Standards for the 6-7 AM (nighttime) Period
Under exceptions contained in Minnesota Rules, commercial noise standards (NAC -2) can be applied to
a residential land use if provisions in the rules can be met. The applicable provisions of Minnesota Rule
7030.0050 are presented below.
Subp. 3. Exceptions. The noise area classification for a land use may be changed in the
following ways if the applicable conditions are met.
B. The standards for a building in a noise area classification 2 shall be applied to a building
in a noise area classification 1 if the following conditions are met:
(1) the building is constructed in such a way that the exterior to interior sound level
attenuation is at least 30 dB(A);
(2) the building has year -round climate control; and
(3) the building has no areas or accommodations that are intended for outdoor activities.
Since there are no areas outside of the upper floor that are specifically intended for outdoor use during
the nighttime period, condition (3) of the provisions can be met. Condition (2) will be met if the homes
are required to provide year -round climate control which is planned. Condition (1) can be met if the
exterior to interior sound attenuation of the homes is 30 dBA or greater,
Under NAC -2, the L10 is 70 dBA for both daytime and nighttime periods. Comparisons of the projected
nighttime (6-7 am) L101evels for receptors relative to the NAC -2 L10 70 dBA standard are presented in
Table 33.
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Camden Ridge Traffic Noise Assessment
Table 3.3 6 -7 AM Level s relative to the NAC -2 Standards
It can be seen that the Upper Floor daytime levels will be 3 dBA or more below the L10 70 dBA
standard.
Therefore, all of the homes on the site will comply with the state noise standards if the homes meet or
exceed an exterior to interior noise reduction of 30 dBA.
3.3. Construction needed to provide an Exterior- Interior Noise Reduction of 30 dBA
Proposed construction for the homes in the development is noted below:
Exterior construction proposed:
LP Smart Board
15/32" sheathing
Tyvek wrap
2x6 studs 16 " o.c.
R -19 batt insulation
'/2" gypsum board
Mechanical ventilation system: 3 -ton central air unit
Windows STC 25 -28
Patio doors: STC 25 -28
Entry doors: STC 29
In order to achieve the 30 dBA exterior to interior sound attenuation, STC 28 windows would be required
if windows make up 15% of the wall area, and STC 29 windows if windows account for 20% of the wall
area facing the highway.
David Braslau Associates, Inc. Page 10
L10 6- 7 AM
Re L10 70
Receptor
Ground
2nd Floor
Ground
2nd Floor
LOT1 -3
61
62
-9
-8
LOTt -4
62
64
-8
-6
LOT1 -5
61
67
-9
-3
LOT2 -15/16
61
66
-9
-4
LOT2 -13/14
1 61
66
-9
-4
LOT2 -11/12
61
1 65
-9
-5
LOT2 -9/10
60
64
-10
-6
LOT2 -7/8
59
64
-11
-6
LOT2 -5/6
60
62
-10
-8
It can be seen that the Upper Floor daytime levels will be 3 dBA or more below the L10 70 dBA
standard.
Therefore, all of the homes on the site will comply with the state noise standards if the homes meet or
exceed an exterior to interior noise reduction of 30 dBA.
3.3. Construction needed to provide an Exterior- Interior Noise Reduction of 30 dBA
Proposed construction for the homes in the development is noted below:
Exterior construction proposed:
LP Smart Board
15/32" sheathing
Tyvek wrap
2x6 studs 16 " o.c.
R -19 batt insulation
'/2" gypsum board
Mechanical ventilation system: 3 -ton central air unit
Windows STC 25 -28
Patio doors: STC 25 -28
Entry doors: STC 29
In order to achieve the 30 dBA exterior to interior sound attenuation, STC 28 windows would be required
if windows make up 15% of the wall area, and STC 29 windows if windows account for 20% of the wall
area facing the highway.
David Braslau Associates, Inc. Page 10
Camden Ridge Traffic Noise Assessment
4.0 SUMMARY OF FINDINGS
Traffic noise levels have been predicted for the Camden Ridge residential development northwest of TH
212 in Chanhassen, Minnesota.
The analysis has been performed for nine receptor locations (representing 15 proposed living units
closest to TH 212) both at the ground floor and upper floor level.
An 8 -foot noise wall on top of a berm up to feet in height is proposed along the entire frontage of the
development with TH 212.
With the berm and wall combination, all of the ground level receptors are predicted to be below the
daytime LIO 65 dBA standard for residential land uses. Upper story receptors will experience levels
several dBA above the daytime standard but are not planned for outdoor uses.
Nighttime (6 -7 am) levels at all of the receptor sites are estimated to be over the L10 55 dBA standard.
However, exceptions to the noise standards permit the NAC -2 or Commercial Noise Standard to be
applied which is L10 70 dBA, providing certain conditions are met. With appropriate home construction,
these conditions should be met so that all receptor sites will be in compliance with the state noise
standards.
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