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HomeMy WebLinkAboutCT 94-04; Poinsettia Shores PA 1; Tentative Map (CT) (7)INDOOR AND OUTDOOR NOISE ANALYSIS FOR POINSETTIA SHORES (PLANNING AREA A-1) CITY OF CARLSBAD Report #94-95 June 14, 1994 Prepared For: KAIZA POINSETTIA CORPORATION 7220 Avenida Encinas Suite 200 Carlsbad, CA 92009 Prepared By: Fred Greve, P.E. Tanya Nguyen MESTRE GREVE ASSOCIATES 280 Newport Center Drive Suite 230 Newport Beach, CA 92660-7528 (714)760-0891 oMestestre Greve Associates Planning Area A-l Pagel SUMMARY OF MITIGATION MEASURES REQUIRED FOR POINSETTIA SHORES (PLANNING AREA A-l) CITY OF CARLSBAD EXTERIOR NOISE LEVELS The rear yard areas in Planning Area A-l must comply with the City of Carlsbad outdoor noise standard of 60 CNEL. A number of rear yard areas in the project will be exposed to traffic noise from Avenida Encinas as well as the Interstate 5 Freeway (1-5). The analysis indicates that these rear yard areas will be exposed to a worst case traffic noise level of approximately 64.7 CNEL. Therefore, in order to meet the 60 CNEL noise standard, the rear yards along the roadways will need noise mitigation measures in terms of sound walls. (It should be noted that the noise analysis includes the noise reduction due to the existing slope which locates between the project site and the Interstate 5 Freeway). In order to meet the 60 CNEL noise standard, double noise barriers will be needed for the rear yard areas of Lots 170 through 180 adjacent to Avenida Encinas. (Lot 206 will be an open space). The noise barriers adjacent to Avenida Encinas should be relative to the top of slope. The top of slope refers to the higher elevation between the pad elevation and the roadway elevation. The second noise barrier will be required along the 1-5 Freeway. This second noise barrier will need to be 6 feet in height. The required noise barrier heights and locations are shown below in TableS-land Exhibits. Table S-l REQUIRED NOISE BARRIER HEIGHT AND LOCATION LOT# Barrier Height (feet) *Barrier Height (feet) *Top-of-Wall relative to top of slope along 1-5 Freeway (1-5 Freeway) ALONG AVENIDA ENCINAS/INTERSTATE 5 (below 60 CNEL for outdoor areas) 180 ^ 176 through 179 171 through 175 170 6.0 6.0 5.5 6.0 6.0 6.0 - "~ 114 115 . - •* NOTE: The top of slope refers to the higher elevation between the pad elevation and the roadway elevation. * Double barrier needed along the 1-5 Freeway. The location of this barrier is shown in Exhibit S. The top-of-wall should descend in a linear manner. With the required noise barriers, all outdoor living areas in the project will meet the City's 60 CNEL outdoor noise standard. The noise barriers are required to have a surface density of at least 3.5 pounds per square foot, and have no openings or cracks. They may be constructed of MESTRE GREVE ASSOCIATES Exhibit 2 Noise Barrier Height and Location Mestestre Greve Associates Planning Area A-l Page 2 wood studs with stucco exterior, 1/4 inch plate glass, 5/8 inch plexiglass, any masonry material, or a combination of these material. INTERIOR NOISE LEVELS The buildings along AvenidaEncinas will experience traffic noise levels in excess of 60 dBA CNEL. The analysis indicates that the buildings in the project will experience a worst case traffic noise level of approximately 64.5 dBA. This results in a maximum outdoor to indoor noise building attenuation of approximately 19.5 dBA in order to meet the City of Carlsbad's 45 CNEL interior noise standard. Detailed engineering calculations which demonstrate the noise reduction levels are necessary for residential building attenuation requirements of greater than 20 dB. The noise analysis was based on the architectural plans titled"Poinsettia Shores Planning Areas A-l and A-l, The Village of Deauville", prepared by H Architects Lonmer»Case, April 27,1994. The construction specifications for this project which were utilized in estimating the outdoor to indoor noise reduction are presented below. Roof is attic space construction and incorporates concrete tiles on the exterior with gypsum drywall on the interior surface. This roof includes fiber glass insulation in stud cavity and is sloped. Exterior walls are wood stud construction with stucco siding and minimum 1/2 inch gypsum drywall on the interior. All exterior walls include fiberglass insulation in stud cavity. Standard glass window has minimum single-strength plate glass. Standard sliding glass door has minimum 3116 inch glazed glass. French entry door has solid core 1-314 inch thick wood and weather-stripping. The results of the analysis indicated that with the standard constructions described above, the buildings in the project will achieve; outdoor to indoor noise attenuations of greater than the required maximum noise reduction (19.5 dBA). Therefore, no building upgrades are required for any of the buildings in the project *• A number of units along the roadway will require windows closed to achieve the. interior noise standard of 45 CNEL. In order to assume windows can remain closed to achieve this required attenuation, adequate ventilation with windows closed must be provided per Uniform Building Code. This can be achieved with mechanical ventilation to provide fresh air. The system must supply two air changes per hour to each habitable room including 20% fresh make-up air obtained directly from the outside. The fresh air inlet duct shall be of sound attenuating construction and shall consist of a minimum of ten feet of straight or curved duct, or six feet plus one sharp 90 degree bend. Air conditioning is an adequate substitute for mechanical ventilation as long as it meets the UBC (Section 1205 (c)) requirements. Mechanical ventilation will be required for buildings on Lots 170 through 180 along AvenidaEncinas. c oMestre Greve Associates Planning Area A-l Page3 INDOOR AND OUTDOOR NOISE ANALYSIS FOR POINSETTIA SHORES (PLANNING AREA A-1) CITY OF CARLSBAD 1.0 INTRODUCTION The purpose of this report is to demonstrate compliance of Planning Area A-l with the noise related'Conditions of Approval' placed on the project by the City of Carlsbad. The project calls for the development of single-family residential units. The report addresses the future exterior and interior noise levels at the project site. The project site is located adjacent to AvenidaEncinas and the Interstate 5 Freeway as shown in Exhibit 1. The project will be exposed primarily to traffic noise from these roadways. This study determines the need for any exterior and interior mitigation measures to provide adequate protection for the residential units in the project. 2.0 NOISE CRITERIA The predominant rating scale now in use in California for land use compatibility assessment is the Community Noise Equivalent Level (CNEL). CNEL is a 24 hour time weighted annual average noise level based on the A-weighted decibel. A-weighting is a frequency correction that correlates overall sound pressure levels with the frequency of the human ear. Time weighting refers to the fact that noise that occurs during certain sensitive time periods is penalized for occurring at these times. The evening time period (7 PM to 10 PM) penalizes noises by 5 dB while nighttime (10 PM to 7 AM) noises are penalized by 10 dB. These time periods and penalties were selected to reflect peoples sensitivity to noise as a function of activity. The City of Carlsbad noise standards require that outdoor living areas not exceed a noise level of 60 CNEL. The City's indoor noise standard is 45 CNEL. 3.0 ROADWAY NOISE The noise levels projected in the next section of this report were computed using the Highway Noise Model published by the Federal Highway Administration ("FHWAHighway Traffic Noise Prediction Model", FHWA-RD-77-108, December 1978). The FHWA Model uses traffic volume, vehicle mix, vehicle speed, and roadway geometry to compute the "equivalent noise level". A computer code has been written which computes equivalent noise levels for each of the time periods used in CNEL. Weighting these noise levels and summing them results in the CNEL for the traffic projections used. CNEL contours are found by iterating over many distances until the distance to 60,65, and 70 CNEL contours are found. Mitigation through the design and construction of a noise barrier (wall, berm, or combination wall/berm)is the most common way of alleviating traffic noise impacts. The effect of a noise barrier is critically dependent on the geometry between the noise source and the receiver. A noise barrier effect occurs when the "line of sight" between the source and receiver is penetrated by the barrier. The greater the penetration the greater the noise reduction. The FHWA model was also used here in computerized format to determine barrier heights. The future traffic volume for Avenida Encinas was taken from the traffic study "Traffic Impact MESTRE GREVE ASSOCIATES CITY OF OCEANSIDE CITY OF VISTA CITY OF SAN MARCOS Exhibit 1 Vicinity Map oMestre Greve Associates Planning Area A-1 Page 4 Analysis for Kaiza Poinsettia Development, Zone 9" prepared by P & D Technologies, April 1991. The traffic was projected for Year 2010. A vehicle speed of 40 miles per hour (mph) was utilized. The traffic distribution estimates are based upon traffic surveys, and are considered typical for arterials in Southern California. The traffic volume and speed utilized are presented in Table 1. The time and traffic distributions utilized are presented in Table 2 and is considered a worst case assumption for Avenida Encinas. The truck mix used with the FHWA Model for the I- 5 Freeway were 3.26 percent medium trucks and 3.73 percent heavy trucks obtained from the Caltrans Highway Traffic Manual (1988). Table 1 FUTURE TRAFFIC VOLUME AND SPEED ROADWAY TRAFFIC VOLUME SPEED Avenida Encinas 6,900 40 1-5 Freeway 215,600 60 Table 2 TRAFFIC DISTRIBUTION PER TIME OF DAY IN PERCENT OF ADT VEHICLE TYPE DAY EVENING NIGHT Automobile Medium Truck Heavy Truck 75.51 1.56 0.64 12.57 0.09 0.02 9.34 0.19 0.08 Using the assumptions presented above, the future noise levels were computed. The results are reported here in Table 3 are in terms of distances to the 60, 65, and 70 CNEL contours. These represent the distances from the centerline of the roadway to the contour value shown. Note that the values given in Table 3 do not take into account the effect of intervening topography that may affect the roadway noise exposure. In addition, the wall and observer are calculated per the FHWA Manual and are included in the Appendix. oMesitre Greve Associates Planning Area A-1 PageS Table 3 DISTANCE TO NOISE CONTOURS FOR FUTURE TRAFFIC CONDITIONS ROADWAY SEGMENT DISTANCE TO CNEL CONTOUR (FT) -70- -65- -60- AVENIDAENCINAS 19 42 90 The results in Table 3 indicate that the rear yard areas along AvenidaEncinas and the 1-5 Freeway will be exposed to traffic noise levels in excess of 60 CNEL. The nearest rear yard will experience a worst case combined traffic noise level of approximately 64.7 CNEL. The nearest building along Avenida Encinas will experience a worst case traffic noise level of approximately 64.5 CNEL. These noise levels include the shielding due to the natural existing slope between the project site and the freeway. 4.0 EXTERIOR NOISE MITIGATION Mitigation through the design and construction of a noise barrier (wall, berm, or combination wall/berm) is the most common way of alleviating traffic noise impacts. The effect of a noise barrier is critically dependent on the geometry between the noise source and the receiver. A noise barrier effect occurs when the "line of sight" between the source and a 6 foot receiver is broken by the barrier. The greater the distance the sound must travel around the barrier to reach the receiver, the greater the noise reduction of the barrier. The FHWA model was also used here in a computerized format to determine barrier heights. A number of rear yard areas in the project will be exposed to traffic noise from AvenidaEncinas as well as the Interstate 5 Freeway (1-5). The analysis indicates that these rear yard areas will be exposed to a worst case traffic noise level of approximately 64.7 CNEL. Therefore, in order to meet the 60 CNEL noise standard, the rear yards along the roadways will need noise mitigation measures in terms of sound walls. (It should be noted that the noise analysis includes the noise reduction due to the existing slope which locates between the project site and the Interstate 5 Freeway). i In order to meet the 60 CNEL noise standard, double noise barriers will be needed.for the rear yard areas of Lots 170 through 180 adjacent to Avenida Encinas. The noise barriers adjacent to Avenida Encinas should be relative to the top of slope. The top of slope refers to the higher elevation between the pad elevation and the roadway elevation. The second noise barrier will be required along the 1-5 Freeway. This second noise barrier will need to be approximately 6 feet in height. The required noise barrier heights and locations are shown below in Table 4 and Exhibit 2. o Mestre Greve Associates Planning Area A-1 Page 6 Table 4 REQUIRED NOISE BARRIER HEIGHT AND LOCATION LOT# Barrier Height (feet) *Barrier Height (feet) *Top-of-WaU relative to top of slope along 1-5 Freeway (1-5 Freeway) ALONG AVENIDA ENCINAS/INTERSTATE 5 (below 60 CNELfor outdoor areas) 180 6.0 6.0 114 176 through 179 6.0 6.0 115 171 through 175 5.5 170 6.0 NOTE: The top of slope refers to the higher elevation between the pad elevation and the roadway elevation. * Double barrier needed along the 1-5 Freeway. The location of this barrier is shown in Exhibit 2. The top-of-wall should descend in a linear manner. The above required noise barriers will cause the combined noise levels for all outdoor living areas to fall below 60 CNEL. The noise barriers are required to have a surface density of at least 3.5 pounds per square foot, and have no openings or cracks. They may be constructed of wood studs with stucco exterior, 1/4 inch plate glass, 5/8 inch plexiglass, any masonry material, or a combination of these material. 7.0 INTERIOR NOISE LEVELS The buildings along Avenida Encinas will be experience a worst case traffic noise level of approximately 64.5 CNEL. Therefore, these buildings will require a worst case outdoor to indoor noise attenuation of 19.5 dBA in order to meet the City of Carlsbad 45 CNEL interior noise standard. Detailed engineering calculations which demonstrate the noise reduction levels are necessary fpX residential building attenuation requirements of greater than 20 dB. To comply with the interior noise standard the buildings must provide sufficient outdoor to indoor building attenuation to reduce the noise levels down to acceptable levels. The outdoor to indoor noise reduction characteristics of a building are determined by combining the transmission loss of each of the building elements which make up the building. Each unique building element has a characteristic transmission loss. For residential units the critical building elements are the roof, walls, windows, doors, attic configuration and insulation. The total noise reduction achieved is dependent on the transmission loss of each element and the area of that element in relation to the total surface area of the room. Room absorption is the final factor used in determining the total noise reduction. For interior noise analysis, the most direct way of computing the total noise reduction is through the use of the methodology published by the Federal Highway Administration ("Insulation of Buildings Against Highway Noise," FHWA TS 77-202). This methodology consists of applying a single number rating concept weighted for highway noise. The FHWA methodology Exhibit 2 Noise Barrier Height and LocationMESTRE GREVE ASSOCIATES Mestre Greve Associates Planning Area A-l Page 7 incorporates the Exterior Wall Noise Rating scale (EWNR). This is similar to the more traditional Sound Transmission Class (STC) rating except that EWNR is specifically weighted for transportation noise sources. The FHWA has published EWNR data for the noise reduction characteristics of various building elements and construction techniques. This noise attenuation data is based upon empirically derived data on construction materials in practice today. The noise analysis were based on the architectural plans titled "Poinsettia Shores Planning Areas A-l and A-l, The Village of Deauville", prepared by H. Architects Lprimer»Case, April 27,1994 The construction specifications for this project which were utilized in estimating the outdoor to indoor noise reduction are presented below. Roof is attic space construction and incorporates concrete tiles on the exterior with gypsum drywallon the interior surface. This roof includes fiber glass insulation in stud cavity and is sloped. Exterior walls are wood stud construction with stucco siding and minimum 112 inch gypsum drywall on the interior. All exterior walls include fiberglass insulation in stud cavity. Standard glass window has minimum single-strength plate glass. Standard sliding glass door has minimum 3116 inch glazed glass. Entry door has solid core 1-314 inch thick wood and weather-stripping. To assess compliance of the project with the interior noise standard, a worst case room for each building plan was selected for analysis. In general, the worst case room is the second story corner room with the greatest amount of window area. Corner rooms have more exterior surface area for noise infiltration. Rooms with large window areas have the least noise reduction, because windows typically are the weakest part of the structure. Table 5 displays some sample of the building element areas and EWNR values (as given by the FHWA) used to compute the total noise reduction. The total outdoor to indoor noise reductions without upgrades are given in Table 5. O o Mestre Greve Associates Planning Area A-1 PageS Table 5 DATA USED TO COMPUTE THE EXTERIOR TO INTERIOR NOISE REDUCTION WITHOUT UPGRADES BUILDING AREA EWNR ELEMENT (SQ. FT.) (DB) without upgrades Plan B - Second Floor Corner Master Bedroom Roof 240 36 Wall 188 40 Window (sliding) 30 22 Window (fixed) 30 26 Total Noise Reduction (dB): 25.5 Worst Case Required Noise Reduction (dB): 19.5 Plan B - Second Floor Corner Master Bedroom (Optional deck) Roof 240 36 Wall 188 40 Window (sliding) 15 22 Window (fixed) 30 26 Door (entry) 19 35 Total Noise Reduction (dB): 26.8 Worst Case Required Noise Reduction (dB): 19.5 Plan C - Second Floor Corner Master Bedroom (Balcony) Roof 322 36 Wall 128 40 Window (sliding) 75 22 Window (entry) 19 35 Total Noise Reduction (dB): 23.8 Worst Case Required Noise Reduction (dB): 19.5 The results show that with the standard construction plans the total outdoor to indoor noise reduction with windows closed for the worst case rooms in each plan is greater than the maximum required attenuation (19.5 dB). Thus, the buildings in the project will meet the interior noise standard of 45 CNEL with no building upgrades as currently designed, assuming windows are closed. With windows open, the outdoor to indoor noise reduction of a building falls to 12 dBA. Therefore windows must be closable for units experiencing an outdoor noise level greater than 57 CNEL. In order to assume windows can remain closed to achieve this required attenuation, adequate ventilation with windows closed must be provided per Uniform Building Code. This can be achieved with mechanical ventilation to provide fresh air. The system must supply two air changes per hour to each habitable room including 20% fresh make-up air obtained directly from the outside. The fresh air inlet duct shall be of sound attenuating construction and shall consist of a minimum of ten feet of straight or curved duct, or six feet plus one sharp 90 degree bend. Air Mestre Greve Associates Planning Area A-1 Page 9 conditioning is an adequate substitute for mechanical ventilation as long as it meets the UBC (Section 1205 (c)) requirements. Mechanical ventilation will be required for buildings on Lots 170 through 180 along Avenida Encinas. Mestre Greve Associates Planning Area A-1 Page 10 APPENDIX DATA USED TO DESIGN NOISE BARRIERS Lot Road Elevation Centerline Distance To To Wall Centerline Base Of Wall Distance To Observer Pad Elevation Observer Height Wall Height ALONG AVENIDAENCINAS 180 178 176 174 172 170 206 180 178 176 90 82 80 77 73.8 70 84 84 82 80 47 47 46 42 42 45 135 130 150 270 90 82 80 77 73.8 70 INTERSTATE 107 108 110 110 65 58 55 52 47 52 5 FREEWAY 280 265 275 440 82 80.7 79.1 76.3 73.8 70.9 84 82 80.7 79.1 6 6 6 6 6 6 6 6 6 6 6.0 6.0 6.0 5.5 5.5 6.0 6.0 6.0 6.0 6.0