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HomeMy WebLinkAboutCDP 98-50; Carlsbad by the Sea; Coastal Development Permit (CDP) (3)Engineering, Planning, Environmental Sciences and Management Services Corporate Office: 605 Third Street Encinitas, California 92024 760.942.5147 Fax 760,632.0164 December 9,1998 2093-01 Mr. Chris Salem SeaGrove Productions 904 West San Marcos Boulevard, Suite 4 San Marcos, CA 92069 PROJECT: Carlsbad by the Sea-APN Lots 214-021-02, 08, 13; APN 214-022-15, 17,27, 28, 33; APN 214-023-05 RE: Environmental Interior Noise Assessment <*Z>~ -* Dear Mr. Salem: Dudek & Associates, Inc., have completed this environmental noise assessment for nine lots within the Carlsbad by the Sea project located in the City of Carlsbad. The assessment has been conducted in conformance with the City of Carlsbad Planning Department's requirement that interior noise levels not exceed 45 dB CNEL within the homes. In summary, to meet the City's interior noise standard, sound-rated windows with minimum STC ratings ranging from 33 to 34 dB will be required for several of the second floor rooms associated with Plot Plans 6, 8 and 9 facing Carlsbad Boulevard. Basic residential grade dual glaze windows are acceptable in all the other rooms associated with Plot Plans 6, 8, and 9. The homes associated with Plot Plans 5, 6, 8, and 9 must be provided with mechanical ventilation or air-conditioning. Also, the interior gypsum board of the exterior wall assemblies must be fastened using resilient channels to the studs in the master bedroom and living/dining rooms associated with Plot Plan 6. Alternatively, 3/4-inch thick plywood could be installed, in addition to the proposed 3/8-inch thick plywood to the exterior walls of these rooms. The homes associated with Plot Plans 1 through 4, and 7 do not require interior noise mitigation measures. It should also be noted that the interior lots on Surfside Lane and Franciscan Road within the Carlsbad by the Sea subdivision will not require interior noise mitigation measures. 1.0 BACKGROUND Project Setting The Carlsbad by the Sea project site is located at the southeast corner of Carlsbad Boulevard and Island Way (Figure 1). This noise analysis evaluates the interior noise level at nine of the lots within NORTH Carlsbad by the Sea Interior Noise Analysis Vicinity & Location Map Mr. Chris Salem December 9,1998 Page 3 the subdivision. The numbered lots in Figure 1 identify the specific Plot Plans associated with each of the lots. The subdivision is composed of 40 lots that will be developed with custom specification single family homes. Several homes are currently under construction or are occupied. This analysis is based on the site plan and architectural drawings (Saunders and Wiant Architects, 4/15/98 and Shinji Isaacs, no date). The primary noise source at the site is vehicular traffic along Carlsbad Boulevard and railway operations along the San Diego Northern Railroad (SDNR). Traffic noise from Avenida Encinas, as well as distant traffic noise from Interstate 5 also moderately affects the site. Carlsbad Boulevard is currently constructed as a four-lane road adjacent to the site. Avenida Encinas is currently constructed as a two-lane road. The existing traffic volume along Carlsbad Boulevard is approximately 15,500 average daily traffic (ADT) (City of Carlsbad, 1998). The existing traffic volume along Avenida Encinas is approximately 3,900 ADT. The site is outside the McClellan- Palomar Airport influence area (SANDAG, 1994). Several project improvements have been completed including the grading of the lots and construction of approximate 5 to 6-foot high masonry walls along the property lines facing Carlsbad Boulevard and the SDNR railway. City Interior Noise Criteria The City of Carlsbad requires that interior noise levels not to exceed a Community Noise Equivalent Level (CNEL) of 45 dB. Attachment 1 contains definitions of acoustical terms used in this report. All sound levels discussed in this report are A-weighted. Methodology The noise analysis methodology in this study is based on the City's noise assessment methodology documented in the City's Noise Guidelines Manual (City of Carlsbad, 1995). Future noise levels were determined based on ambient noise measurements along Carlsbad Boulevard, and by using Caltrans' SOUND32 Highway Traffic Noise Prediction Model (Caltrans, 1983) with California noise emission factors (Caltrans, 1987). The noise model is based on the Federal Highway Administration's traffic noise prediction model (FHWA, 1978). Input in the noise model included the buildout traffic volume of 34,600 ADT along Carlsbad Boulevard and 10,500 ADT along Avenida Encinas (City of Carlsbad, 1998) with the posted vehicle speeds of 50 mph along Carlsbad Boulevard and 30 mph along Avenida Encinas. The truck mix used for the roads was 3.52 percent c o Mr. Chris Salem December 9, 1998 Page 4 medium trucks and 1.24 percent heavy trucks. The traffic mix is based on vehicle mix surveys conducted by the City (City of Carlsbad, 1995). A hard site noise propagation factor was used for the future conditions. Train noise was determined based on conducting wayside noise measurements at the project site during several passenger train pass-bys and supplemented with freight train noise measurements conducted approximately 0.5 miles north of the site. The sound exposure level (SEL) for several train events was measured. 2.0 EXISTING CONDITIONS Ambient Noise Monitoring Noise measurements were conducted at the site to determine the existing noise level. The measurements were made using a calibrated Larson-Davis Laboratories Model 700 (S.N. 2132) integrating sound level meter equipped with a Bruel & Kjaer Type 4176 '/2-inch pre-polarized condenser microphone with pre-amplifier. When equipped with this microphone, the sound level meter meets the current American National Standards Institute standard for a Type 1 precision sound level meter. A second Larson-Davis Laboratories Model 700 meter (S.N. 0724) was also used. The second meter meets the ANSI standard for a Type 2 (general-purpose) sound level meter. Four noise measurement locations were selected at the project site and are depicted as Sites 1 through 4 on Figure 2. Sites 1 and 2 are approximately 70 feet and 85 feet, respectively, from the closest railway track. Sites 3 and 4 are approximately 95 feet and 110 feet, respectively, from the center line of Carlsbad Boulevard. At Sites 1 and 4 the sound level meters were positioned above the existing walls to determine the noise level without the attenuation effects of the masonry walls. At Sites 2 and 3 the sound level meters were positioned at a height of approximately five feet above the ground to determine the sound level associated with the attenuation of the existing walls. Concurrent traffic counts were conducted during the noise measurements at Sites 3 and 4. The measured average noise level was 60 dB at Site 3 and 68 dB at Site 4. Table 1 shows the measured noise levels and the concurrent traffic volumes. Wayside noise measurements were conducted at Sites 1 and 2 during several Coaster and Amtrak train pass-bys. At Site 1 the measured sound exposure level (SEL) varied from 87 to 91 dB for the Coaster trains and 91 to 98 dB for the Amtrak trains. At Site 2 the measured SEL varied from 76 Existing 5'-6' High Sound Wall Along Boundary Existing 5'-6' High Sound Wall Along Boundary BASE MAP SOURCE: City of Carlsbad Engineering Department Carlsbad by the Sea interior Noise Analysis Noise Measurement Locations Mr. Chris Salem December 9,1998 Page 6 to 82 dB for the Coaster trains and 76 to 84 dB for the Amtrak trains. TABLE 1 MEASURED NOISE LEVELS AND TRAFFIC VOLUMES Site 3 4 Description 105 feet from Center Line to Carlsbad Boulevard;behind wall 95 feet from Center Line to Carlsbad Boulevard Date Time 12/2/98 4:45 to 5:05 pm 12/2/98 4:45 to 5:05 pm LJ 60 dB 68 dB Cars 403 403 MT2 1 1 HT3 1 1 Notes:1 Time-Average Sound Level (Equivalent Continuous Sound Level) 2 Medium Trucks 3 Heavy Trucks General Notes: Temperature 60 degrees, light westerly wind. Traffic Noise Modeling The existing CNEL was calculated for the traffic noise measurement locations based on the current traffic volume along Carlsbad Boulevard using Caltrans' SOUND32 noise model. To verify the input used in the noise model, the same traffic volume and vehicle composition ratios counted during the noise measurements were used. The modeled value was within one dB of the measured noise level which confirms the assumptions used in the noise model. The CNEL at the measurement sites was calculated by adjusting the traffic volume and truck percentage to a set of normalized conditions (i.e., the City traffic mix and existing ADT). The existing traffic generated CNEL at Sites 3 and 4 is calculated to be 62 and 70 dB, respectively. Rail Noise The SDNR is aligned along the eastern portion of the site. Based on a review of the latest train c Mr. Chris Salem December 9,1998 Page? schedules, approximately 18 commuter trains (Coaster) and 22 inter-city trains (Amtrak) are scheduled each weekday. The majority of the Coaster and Amtrak trains run between the hours of 7:00 a.m. to 10:00 p.m. Four freight trains generally use the railway each day, although these freight trains are not on a set time schedule. For the purposes of this study it is assumed that two freight trains run between the hours of 7:00 a.m. to 10:00 p.m., and two freight trains run between 10:00 p.m. and 7:00 a.m. The CNEL for the rail traffic was calculated using the measured SEL for each type of train (i.e., Coaster, Amtrak and freight trains). The results of the calculation indicate that the CNEL is approximately 65 dB at Site 1 and 53 dB at Site 2. 3.0 ANALYSIS Interior noise levels were calculated based on a review of the floor plans. The calculations take into consideration the exterior noise level, the construction of the exterior facade, the floor plans and orientation of the homes to Carlsbad Boulevard and the SDRR. There are nine floor plans. All the floor plans are for two story homes. The Sound Transmission Class (STC) ratings assumed were STC 26 for dual-glazed sliding glass windows and STC 29 for dual-glazed fixed windows. Almost any residential grade window can achieve this level of noise reduction. The exterior wood sided walls of the homes will have a STC rating of 40 dB. The stucco walls of the homes will have a STC rating of 46. With the windows open, the interior CNEL associated with Plot Plans 5, 6, 8, and 9 would exceed the City's interior noise standard of 45 dB. With the windows assumed to be closed, and with basic residential grade windows, the resulting interior CNEL at the second floor rooms facing Carlsbad Boulevard is calculated to range up to approximately 53 dB associated with Plot Plans 6, 8 and 9. The interior CNEL at the rooms facing the SDRR is calculated to range up to approximately 42 dB associated with Plot Plan 5. Attachment 2 includes representative interior noise calculations. The interior CNEL at the remaining first and second floor rooms facing away from Carlsbad Boulevard associated with Plot Plans 6, 8, and 9 will be 45 dB or less. The interior CNEL in all the remaining homes associated with Plot Plans 1, 2, 3, 4, 7 are calculated to be 45 dB or less with the windows open. The noise level would be less than 45 dB CNEL due to the existing noise barriers reducing the exterior traffic and railroad noise, in conjunction with the proposed building setbacks, orientations and building materials. It should be noted that the ulterior noise level at all the interior lots along Surfside Lane and Franciscan Road will similarly be exposed to a CNEL Mr. Chris Salem December 9,1998 Page 8 of less than 45 dB with the windows open and will not require interior noise mitigation measures. 4.0 MITIGATION Several rooms associated with Plot Plans 6, 8 and 9 will require interior noise mitigation. To meet the City's interior noise design criteria will require sound-rated windows with minimum STC ratings ranging from 33 to 34 dB. Table 2 summarizes the minimum STC ratings required for the windows and glass doors for each of the rooms to meet the City's interior noise criteria. Basic residential grade dual glaze windows are acceptable in all the other rooms. In addition, the following two items are also required: A. . The interior gypsum boards of the exterior wall assemblies must be fastened to the studs using resilient channels in the master bedroom and living/dining room in Plot Plan 6. Alternatively, 3/4-inch thick plywood could be installed, in addition to the proposed 3/8- inch thick plywood, to the exterior walls of these rooms. B. The homes associated with Plot Plans 5, 6, 8 and 9 must be provided with either air conditioning and/or mechanical ventilation. The mechanical ventilation should be in accordance with Section 12.05.(c) of the 1994 edition of the Uniform Building Code. TABLE 2 MINIMUM STC RATINGS FOR WINDOWS/GLASS DOORS Plot Plan APN Room STC Rating 6 214-021-13 Master Bedroom (all windows) 34 Living/Dining Room (all windows) 34 Living/Dining Room (French door) 33 8 214-021-02 Master Bedroom (all windows) 34 Great/Dining Room (all windows) 34 Great/Dining Room (sliding glass door) 33 9 214-021-08 Bedroom 2 (all windows) 33 Master Bedroom (all windows) 33 Mr. Chris Salem December 9, 1998 Page 9 This concludes our noise assessment. If you have any questions, please call me. Very truly yours, DUDEK & ASSOCIATES, INC. Mike Komula Acoustician REFERENCES California Department of Transportation (Caltrans), June 1983. User's Instructions for SOUND32 (FHWA/CA-83/06). California Department of Transportation (Caltrans), 1987. California Vehicle Noise Emission Levels, (FHWA/CA/TL-87/03). Carlsbad, City of, September 1995. City of Carlsbad Noise Guidelines Manual. Carlsbad, City of, December 2, 1998. Telephone Conversation with Mr. Jim Gales, City Traffic Engineering Department. Federal Highway Administration (FHWA), 1978. FHWA Highway Traffic Noise Prediction Model (FHWA-RD-77-108). San Diego Association of Governments (SANDAG), April 1994. Comprehensive Land Use Plan McClellan-Palomar Airport Carlsbad, California. ATTACHMENT 1 DEFINITIONS Term Definition Ambient Noise Level A-Weighted Sound Level Community Noise Equivalent Level, CNEL Decibel, dB Time-Average Sound Level, TAV Maximum A-weighted Sound Level, Ln Sound Transmission Class, STC The composite of noise from all sources near and far. The normal or existing level of environmental noise at a given location. The sound pressure level in decibels as measured on a sound level meter using the A-weighted filter network. The A-weighting filter de-emphasizes the very low and very high frequency components of the sound in a manner similar to the frequency response of the human ear and correlates well with subjective reactions to noise. CNEL is the A-weighted equivalent continuous sound exposure level for a 24-hour period with a ten dB adjustment added to sound levels occurring during nighttime hours (10 pm to 7 am) and a five dB adjustment added to the sound levels occurring during the evening hours (7pm to 10 pm). The sound level corresponding to a steady state sound level containing the same total energy as a varying signal over a given sample period. TAV is designed to average all of the loud and quiet sound levels occurring over a time period. The greatest sound level measured on a sound level meter during a designated time interval or event using fast time-averaging and A-weighting. A single number rating of the noise reduction of a building element. EXTERIOR TO INTERIOR NOISE LEVEL CALCULATION ROOM:Lot 8-Plan 9-Bedroom 2-west wall Noise Source Code CNEL Carlsbad Boulevard 120 73 Exterior Sound Pressure Level (dB re 20 uPa) lOOHz 125Hz 160H2 200Hz 250Hz 315Hz 400Hz SOOHz 630Hz 800Hz 1kHz .25kH 1.6kHz 2kHz 2.5kHz .15kH 4kHz 71 70 69 67 67 67 69 68 66 63 63 62 60 59 57 53 51 Transmission Loss (dB) Element Dual Glaze Operable STC 33 Stucco Siding w/o channels STC 46 Code 10 50 0 0 0 Area 20 88 0 0 0 lOOHz 125Hz 22 23 25 25 160Hz 200Hz 27 27 30 42 250Hz 315Hz 400Hz 27 28 28 41 44 43 500Hz 630Hz SOOHz 29 30 31 45 45 46 1kHz 35 45 .25kH 35 46 1.6kHz 37 48 2kHz 2.5kHz 36 34 50 50 .15kH 4kHz 34 33 50 55 Composite TL 24 25 29 34 34 35 35 36 37 38 41 41 43 43 41 41 40 Total Room Absorption Absorption Coefficients Surface Glass Gypsum board Carpet on pad Code 80 81 100 0 0 0 Area 40 516 155 0 0 0 lOOHz 0.35 0.30 0.08 125Hz 0.35 0.29 0.10 160Hz 0.30 0.25 0.12 200Hz 0.25 0.15 0.15 250Hz 0.25 0.10 0.19 315Hz 0.20 0.08 0.25 400Hz 0.20 0.07 0.30 SOOHz 0.18 0.05 0.35 630Hz 0.15 0.05 0.45 SOOHz 0.15 0.05 0.50 1kHz 0.12 0.04 0.79 .25kH 0.10 0.05 0.78 1.6kHz 0.08 0.05 0.74 2kHz 0.07 0.07 0.69 2.5kHz 0.06 0.07 0.70 .15kH 0.05 0.08 0.73 4kHz 0.04 0.09 0.79 181 179 160 111 91 88 91 87 102 109 148 151 144 146 147 157 171 Sound Pressure Level (dB re 20 uPa) Sound Levels Exterior A-Weighted Sound Level Interior A- Weighted Sound Level Exterior CNEL 73 Interior CNEL 43 lOOHz 125Hz 160Hz 200Hz 250Hz 315Hz 400Hz SOOHz 630Hz SOOHz 1kHz .25kH 1.6kHz 2kHz 2.5kHz .ISkH 4kHz 52 54 56 56 58 60 64 65 64 62 63 63 61 60 58 54 52 31 33 31 28 32 32 36 36 34 30 27 26 23 22 22 18 16 0(056 EXTERIOR TO INTERIOR NOISE LEVEL CALCULATION ROOM:Lot 8-Plan 9-Bedroom 2-south wall Exterior Sound Pressure Level (dB re 20 uPa) Noise Source Code CNEL Carlsbad Boulevard 120 70 Element code Dual Glaze Operable STC 33 1 0 Stucco Siding w/o channels STC 46 50 0 0 0 Composite TL Surface code Glass 80 Gypsum board 81 Carpet on pad 100 0 0 0 Total Room Absorption Sound Levels lOOHz 125Hz 160Hz 200Hz 250Hz 315Hz 400Hz SOOHz 630Hz SOOHz 1kHz .25kH 1.6kHz 2kHz 2.5kHz 68 67 66 64 64 64 66 65 63 60 60 59 57 56 54 Transmission Loss (dB) Area lOOHz 125Hz 160Hz 200Hz 250Hz 315Hz 400Hz SOOHz 630Hz SOOHz 1kHz .25kH 1.6kHz 2kHz 2.5kHz 20 22 23 27 27 27 28 28 29 30 31 35 35 37 36 34 72 25 25 30 42 41 44 43 45 45 46 45 46 48 50 50 0 0 0 24 24 29 33 33 34 34 35 36 37 40 41 43 42 40 Absorption Coefficients Area lOOHz 125Hz 160Hz 200Hz 250Hz 315Hz 400Hz SOOHz 630Hz SOOHz 1kHz .25kH 1.6kHz 2kHz 2.5kHz 40 0.35 0.35 0.30 0.25 0.25 0.20 0.20 0.18 0.15 0.15 0.12 0.10 0.08 0.07 0.06 516 0.30 0.29 0.25 0.15 0.10 0.08 0.07 0.05 0.05 0.05 0.04 0.05 0.05 0.07 0.07 155 0.08 0.10 0.12 0.15 0.19 0.25 0.30 0.35 0.45 0.5U 0.79 0.78 0.74 0.69 0.70 0 0 0 181 179 160 111 91 88 91 87 102 109 148 151 144 146 147 Sound Pressure Level (dB re 20 uPa) lOOHz 125Hz 160Hz 200Hz 250Hz 315Hz 400Hz SOOHz 630Hz SOOHz 1kHz .25kH 1.6kHz 2kHz 2.5kHz .15kH 4kHz 50 48 .15kH 4kHz 34 33 50 55 40 40 ,15kH 4kHz 0 05 0 04 0.08 0.09 0.73 0.79 157 171 .ISkH 4kHz Exterior A-Weighted Sound Level Interior A-Weighted Sound Level Exterior CNEL 70 Interior CNEL 40 49 28 51 30 53 27 53 25 55 28 57 29 61 33 62 33 61 31 59 27 60 24 60 23 58 20 57 19 55 19 51 15 49 13