Traffic Noise Assessment 04-02-2013 The Preserve at Rice Lake Chanhassen, Minnesota TRAFFIC NOISE ASSESSMENT Prepared for J. & S. Venture 1, Inc. 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 April 2013
The Preserve at Rice Lake Traffic Noise Assessment David Braslau Associates, Inc. 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.............................................................................................9 3.1. Predicted Noise Levels....................................................................................................9 3.2. Compliance with State Standards for the 6-7 AM (nig httime) Period..........................11 3.3. Construction needed to provide an Exterior-Interior Noise Reduction of 30 dBA.......12 4.0 SUMMARY OF FINDINGS...........................................................................................13
The Preserve at Rice Lake Traffic Noise Assessment David Braslau Associates, Inc. List of Figures Figure 1.1 Site Location..........................................................................................................2 Figure 1.2 Site Layout and Grading Plan..............................................................................3 Figure 2.1 Location of Receptor Sites....................................................................................6 Figure 2.2 Location of the Noise Wall Relative to the Homes an d TH 212........................7 List of Tables Table 1.1 Minnesota State Noise Standards for Residential Lan d Uses (NAC-1)...........1 Table 3.1 Predicted L10 for the PM Peak Hour.................................................................9 Table 3.2 Predicted L10 for the 6-7 AM Hour..................................................................10 Table 3.3 6-7 AM Level s relative to the NAC-2 Standards.............................................12
The Preserve at Rice Lake Traffic Noise Assessment David Braslau Associates, Inc. Page 1 1.0 INTRODUCTION 1.1. Objectives of this Noise Assessment This Noise Assessment evaluates the potential impacts of noise from Trun k Highway 212 on the proposed Preserve at Rice Lake residential developm ent in Chanhassen, Minnesota. Projected traffic noise levels primarily from TH 21 2 but also 11 other roadways in the area are compared with the Minnesota daytime and nighttime n oise 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 Preserve at Rice Lake with 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 level s. 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 (No ise Area Classification -1) under Minnesota Rule 7030.0040. Table 1.1 Minnesota State Noise Standards for Resid ential Land Uses (NAC-1) Daytime (7:00 am to 10:00 pm Nighttime (10:00 pm t o 7:00 am L10 65 dBA 55 dBA L50 60 dBA 50 dBA L10 is the level exceeded 10% or 6 minutes of an ho ur. L50 is the level exceeded 50% or 30 minutes of an hour. The L10 level is used as the p rimary indicator of traffic noise impact since it accurately reflects the potential impact of traffic .
The Preserve at Rice Lake Traffic Noise Assessment David Braslau Associates, Inc. Page 2 Figure 1.1 Site Location SITE
The Preserve at Rice Lake Traffic Noise Assessment David Braslau Associates, Inc. Page 3 Figure 1.2 Site Layout and Grading Plan
The Preserve at Rice Lake Traffic Noise Assessment David Braslau Associates, Inc. Page 4 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 traff ic noise and compliance with state noise standards. Section 4.0 presents a summary of findings.
The Preserve at Rice Lake Traffic Noise Assessment David Braslau Associates, Inc. Page 5 2.0 METHODOLOGY FOR ANALYZING HIGHWAY NOISE Noise levels from TH 212 have been predicted using the MinnNoise highway noise model supplied by MnDOT for the original noise study of t his property in 2007. Noise levels are evaluated at receptors at each of the proposed lots and 5 feet above ground level normally used to evaluate the benefits of highway noise barriers. N oise levels are also evaluated at the upper floors of homes proposed for each lot. Predicted traffic noise levels are compared with th e Minnesota state noise standards to determine compliance with the standards. 2.1. Noise Modeling Assumptions The MnDOT Noise file contains geometry and roadway elevations for TH 12. Elevations of the actually constructed noise walls immediately west o f the proposed development were estimated from photographs and berm heights on the grading pl an. As seen on Figure 2.1 and Figure 2.2 , the existing wall extends east of the Preserve at R ice Lake property line. The model includes geometries, traffic volumes and vehicle mix for13 r oadways in the area that could potentially impact noise levels at the proposed development. A noise wall is proposed along the entire property fronting TH 212. The wall will extend from the existing noise wall west of the site with a pro posed top-of-wall elevation of 924, except for a section at Elevation 928, with two 24-foot sections either side at Elevation 926. The wall will be 8 feet high on the west berm, 10 feet high on the e ast berm, and higher between the berms and at the east end with a short (~56 ft) wrap-around wall down to the proposed trail. Estimated length of the wall is 1088 feet. Preliminary noise modeling was performed to evaluat e wall elevations needed to ensure compliance with the state noise standards. The res ults presented in this report are based upon this wall design. The model geometry in the vicinity of the proposed development with the proposed home locations and barrier are shown on Figure 2.1 . Numbers above each home site refer to receptor site numbers in the noise model and do not necessar ily correspond to lot numbers. Some limited shielding of noise is assumed to be provided by hom es receptors 1, 2, 3, and 4. A short wrap-around section of the wall is assumed on the east e nd that extends from the top of the berm to the proposed trail. Location of the proposed noise wal l relative to the homes and TH 212 is shown on Figure 2.2 . A profile of the assumed noise barrier is shown on Figure 2.3 .
The Preserve at Rice Lake Traffic Noise Assessment David Braslau Associates, Inc. Page 6 Preserve at Rice Lake 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 175000 175200 175400 175600 175800 176000 176200 176400 176600 560500560700560900561100561300561500561700561900562 100562300562500562700562900563100 East North Existing wall Proposed new wall TH212 WB Figure 2.1 Location of Receptor Sites
The Preserve at Rice Lake Traffic Noise Assessment David Braslau Associates, Inc. Page 7 Figure 2.2 Location of the Noise Wall Relative to t he Homes and TH 212 Noise Noise Wall
The Preserve at Rice Lake Traffic Noise Assessment David Braslau Associates, Inc. Page 8 Profile with Noise Walls - With El 928 Segment (vertical scale exaggerated)880 890 900 910 920 930 940 560500561000561500562000562500563000563500 564000 East Elevatoin Top of wall Top of berm Wall wrap (~ 56 ft)Berm 160 ft section at El 928 Existing wall Proposed new El 924 TH 212 Ground Floor Receptors Upper level receptors Figure 2.3 Proposed Noise Wall Profile
The Preserve at Rice Lake Traffic Noise Assessment David Braslau Associates, Inc. Page 9 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 second floor at each of the receptor sites are show n in Table 3.1 . The last two columns show the predicted L10 level relative to the daytime standar d 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 Receptor Ground 2nd Floor Ground 2nd Floor 16367-22 26367-22 36165-40 46264-4-1 56164-4-1 66264-4-1 76265-30 86264-3-1 96163-4-2 106162-5-3 116062-5-3 126162-4-3 136162-4-3 146162-4-3 156263-3-2 16 63 65 -2 0 L10 PMRe Day Standard It can be seen from the table that all of the groun d floor receptors are predicted to be below the day time noise standard. The 2 nd floor level of the two closest homes is estimated to be 2 dBA over the daytime standard. With appropriate home construction requi red for compliance with the nighttime standard (see discussion in Section 3.2, the applicable L10 stand ard will be 70 dBA, so that these homes should also be in compliance with the state noise standards.
The Preserve at Rice Lake Traffic Noise Assessment David Braslau Associates, Inc. Page 10 Sound levels have also been estimated for the 6-7 A M period assuming 60% of the PM peak traffic which is a typical value for this important commuti ng hour. These levels are presented in Table 3.2 . The last column shows the predicted L10 level re lative to the nighttime standard of 55 dBA. All levels are expressed in dBA (A-weighted decibel s). Table 3.2 Predicted L10 for the 6-7 AM Hour Receptor Ground 2nd Floor Ground 2nd Floor 16165610 26165610 3596348 4606257 5596247 6606257 7606358 8606257 9596146 10596045 11586035 12596045 13596045 14596045 15606156 16 61 63 6 8 L10 6- 7 AMRe Night Standard It can be seen that the predicted 6-7 AM L10 levels exceed the nighttime level by as much as 10 dBA on the upper floor. However, exceptions to the Minnes ota 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.
The Preserve at Rice Lake Traffic Noise Assessment David Braslau Associates, Inc. Page 11 3.2. Compliance with State Standards for the 6-7 AM (nig httime) Period Under exceptions contained in Minnesota Rules, comm ercial noise standards (NAC-2) can be applied to a residential land use if provisions in the rules c an be met. The applicable provisions of Minnesota Rule 7030.0050 are presented below. Subp. 3. Exceptions. The noise area classificatio n 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 a rea classification 2 shall be applied to a building in a noise area classification 1 if the following c onditions are met: (1) the building is constructed in such a w ay that the exterior to interior sound level attenuation is at least 30 dB(A); (2) the building has year-round climate con trol; and (3) the building has no areas or accommodat ions that are intended for outdoor activities. Since there are no areas outside of the upper floor that are specifically intended for outdoor use dur ing the nighttime period, condition (3) of the provisio ns can be met. Condition (2) will be met if the ho mes are required to provide year-round climate control, which is generally standard for new homes in Minnesota that comply with the state energy code. Condition (1) can be met if the exterior to interio r 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) L10 levels for receptors relativ e to the NAC-2 L10 70 dBA standard are presented in Table 3.3.
The Preserve at Rice Lake Traffic Noise Assessment David Braslau Associates, Inc. Page 12 Table 3.3 6-7 AM Level s relative to the NAC-2 Stan dards Receptor Ground 2nd Floor Ground 2nd Floor 16165-9-5 26165-9-5 35963-11-7 46062-11-8 55962-11-8 66062-11-8 76063-10-7 86062-10-8 95961-11-9 105960-12-10 115860-12-10 125960-11-10 135960-11-10 145960-11-10 156061-10-9 16 61 63 -9 -7 L10 6- 7 AMRe L10 70 The 2 nd Floor daytime levels for receptors 1 and 2 will be 3 dBA below the L10 70 dBA standard. Therefore, if an exterior-interior noise reduction of 30 dBA can be provided, all of the homes on the site will comply with the state noise standards if the h omes 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 Typical exterior wall construction for new homes in Minnesota is based upon 2x6 studs, with exterior sheathing and siding, interior cavity absorption, a nd at least one layer of gypsum board or similar material in the interior of the wall. Previous exp erience and data indicates that a wall of this type will provide an STC 47. A review of the typical house p lan for the site shows that the 30 dBA noise reduction can be achieved for the back and side ele vations with only STC 26 windows, although most insulating glass widows provide an STC 28. The 30 dBA can be achieved for the front elevation with STC 28 windows.
The Preserve at Rice Lake Traffic Noise Assessment David Braslau Associates, Inc. Page 13 4.0 SUMMARY OF FINDINGS Traffic noise levels have been predicted for the Pr eserve at Rice Lake location north of TH 212 in Chanhassen, Minnesota. The analysis has been performed for sixteen recepto r locations both at the ground floor and upper or 2 nd story level. A noise wall on top of the existing berms that will extend the existing noise wall to the west is prop osed. The top of the wall elevation is 924 and the wall v ary in height from 8 feet on the west to 10 feet on the east, with a higher wall between the berms and on t he east end, where a short wrap-around wall is proposed. With the wall, all of the ground level receptors ar e predicted to be below the daytime L10 65 dBA standard for residential land uses. All 2 nd story receptors are also predicted to be below the standard except the two closest, which are estimated to be o nly 2 dBA over the daytime standard. Nighttime (6-7 am) levels at all of the receptor si tes are estimated to be over the L10 55 dBA standar d. However, exceptions to the noise standards permit t he NAC-2 or Commercial Noise Standard to be applied which is L10 70 dBA, providing certain cond itions 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. y:\jobs\2013jobs\213019\report\the_preserve_at_rice _lake_noise_assessment.doc