Loading...
HomeMy WebLinkAboutCT 91-07; La Vercia Condominiums; Tentative Map (CT) (14)Report No. 9110-R June 22, 1992 JAMES C. BERRY - ACOUSTICIAN 2401 Trace Road Spring Valley, CA 91978 (619) 660-0064 REPORT ON AN ACOUSTICAL STUDY La Vercia Condominiums Tamarack Avenue, Carlsbad CP 91-04; CT 91-07 Prepared for: A.R.C. Group 5751 Palmer Way, Suite H Carlsbad, CA 92008 by: James C. Berry Acoustician James C. Berry - Acoustician Report No. 9110-R (619) 660-0064 Page 1 REPORT ON AN ACOUSTICAL STUDY La Vercia Condominiums, Tamarack Avenue, Carlsbad CP 91-04; CT 91-07 INTRODUCTION This report is a revision of the original document No. 9110, is- sued on April 22, 1991 and has been necessitated by a significant change in the Tentative Map and Site Development Plan. It was not deemed necessary to repeat the noise measurements on the site, so the existing conditions shown below are as originally reported and refer to the year 1991. The future traffic flow on Tamarack Ave- nue has been confirmed with the City Traffic Engineer and the fu- ture noise levels on the site and at the buildings have been re- calculated in order to reflect the project changes. The proposed 5 unit "La Vercia" condominium project is located on the south side of Tamarack Avenue, east of Garfield Street and about 350 feet west of the Santa Fe Railroad tracks in the City of Carlsbad, California. The site is outside the 3 mile radius area of influence of McClel- lan Palomar Airport but is within 500 feet of a railroad right-of- way and close to an important street. A noise study is required under the Noise Control Act of 1973, Health and Safety Code 46000 et.seq.; the Planning and Zoning Law Government Code 65302 (f); CEQA Public Resource Code 2100 et.seq., and City of Carlsbad Poli- cy No.17, in lieu of the updated Noise Element of the General Plan. EXISTING CONDITIONS The site has a 65 foot frontage along Tamarack Avenue and is ap- proximately 312 feet long. At the time of the measurement it was unoccupied with some shrubs and an empty house pad at the road end, while the remainder was covered with long wild grasses (see partial Site Plan, Figure 1.) Tamarack Avenue is a two-lane street with a center double yellow line, no parking lane, gutter, curb or sidewalk at the site. The posted speed limit is 25 mph and the current traffic flow is 9,000 James C. Berry - Acoustician Report No. 9110-R (619) 660-0064 Page 2 Average Daily Trips (ADT) between Jefferson Street and Carlsbad Boulevard (Source: SANDAG Map of Average Weekday Traffic Volumes, 1990 Issue.) [Note: in the 1991 issue, this has been increased to 10,000 ADT. This would cause less than 1/2 dB difference in measured noise levels.] The railroad tracks are owned by the Santa Fe Railroad but are jointly operated by Amtrak. There are sixteen scheduled Aratrak trains every day between San Diego and Los Angeles and return, fairly evenly spread out between about 6:15 a.m. and 10:45 p.m. at Carlsbad (source: Amtrak information.) There are two regu- larly scheduled freight trains per day, one in and one out, but there could also be one or two specials at various times (Source - Santa Fe Railroad Information.) Thus, between eighteen and twenty trains pass the site every day. The site was visited on Friday April 19, 1991, for familiarization purposes and to make noise measurements. Two measurement loca- tions were chosen. The first was 50 feet from the centerline of the nearest traffic lane on Tamarack Avenue (56 feet from the centerline of the right-of-way.) This location is shown in the attached Figure 1. The second location was 10 feet from the rear property line (approximately 300 feet from the road.) Noise measurements were made using a Quest Electronics Precision Integrating Sound Level Meter, Type 1800, Serial No. HP 0050017 in- corporating a Condenser Microphone Type MK 224, Serial No. 89335, with calibrations traceable to the National Bureau of Standards. The sound level meter meets all applicable U.S. and International Standards for Type 1 instruments (ANSI SI.4-1983; IEC 651-1979 and 804-1984). The meter was calibrated prior to use with a CA-22 Pressure Calibrator, Serial No. J.0040042. It was then mounted on a tripod at a height of 1.2 meters from the ground and fitted with a windscreen. The results of the measurements were as follows: Highest Level Lowest Level Average Duration Recorded Recorded Level Lmax-dB(A) Lmin-dB(A) Leq-dB(A) Min. 84* 38 60 31 75* 35 51 26 * Highest level caused by train whistle James C. Berry - Acoustician Report No. 9110-R (619) 660-0064 Page 3 Noise levels created by passing trains were noted separately. At location 1, an Amtrak passenger train travelling south created a maximum level of 84 dB(A) due to the whistle while the engine and cars were much lower in level and passed in about 5 seconds. A Santa Fe freight train travelling north created 80 dB(A) due to the whistle, while the engine and various freight cars created noise levels in the range 65 to 75 dB(A) apparently due to the varying condition of wheels and axle bearings. It took almost 20 seconds to pass. At location 2, the whistle of a second, very short, freight train travelling north produced 75 dB(A) and, again, the train passed in 5 seconds. This lower level whistle was due to shielding from the existing apartment building to the east. The train noise is in- cluded in the measured Leq. The lowest recorded noise levels, in the range 35 to 38 dB(A) Leq, indicate the basic underlying ambient without the intrusive noise sources. These levels are typical of a quiet suburban neighbor- hood. The measurements for a half hour are representative of a typical weekday daytime hourly average noise level [Leq(hour)]. The relationship between the Leq(hour) and the long term community noise levels (CNEL or Ldn) has been found to be: CNEL/Ldn = Leq (hour) + 2 dB(A) Thus, at the two measurement locations the measured community noise levels were 62 and 53 dB(A) CNEL/Ldn respectively. Because of the ground surface, shrubs and grass, the attenuation constant was calculated at 12.5 times the logarithm to the base 10 of the ratio of the distances. It was further calculated that the 1991 noise contours occured as follows: 65 dB(A) CNEL/Ldn - 32 feet from the centerline of Tamarack Ave. 60 dB(A) CNEL/Ldn - 81 feet from the centerline of Tamarack Ave. The 1991 existing 65 and 60 dB(A) contours are shown in Figure 1. FUTURE CONDITIONS WITHOUT PROJECT Even if the proposed project is not built, some future changes along Tamarack Avenue will result in corresponding changes in the noise levels. By the year 2010 the area will be built out and Tamarack Avenue will be carrying 9,700 ADT (Source: Bob Johnson of the City of Carlsbad Traffic Engineering Department.) In addi- tion, Tamarack Avenue will be slightly realigned to bring the centerline 10 feet closer to the site. At measurement location No.l, the noise level would rise by just under 1 dB due to the James C. Berry - Acoustician Report No. 9110-R (619) 660-0064 Page 4 relocation of the centerline and just over 1/4 of a dB due to the rise in traffic. The future noise level at measurement location 1 would therefore be just over 63 dB(A) and the 65 and 60 dB(A) CNEL/Ldn contours would occur at 38 and 83 feet respectively from the new centerline of Tamarack Avenue. These theoretical contours are shown in Figure 1. IMPACTS DUE TO THE PROJECT Construction Noise Construction of the project will cause a significant but temporary noise impact on the surrounding community, especially to the apart- ments directly to the east and west of the site and to the houses across the street. There will be site preparation, grading, pav- ing, foundation laying, building erection and finishing. Typical equipment will be on site during the various phases of construc- tion and, at completion, all of this equipment will be removed and the noise will cease. Construction noise is not covered in Policy 17 but is normally regulated by limiting the hours of operation and by forbidding such activities on Sundays or public holidays. Contractors should be required to use properly muffled and well maintained equipment. Project Noise The project will introduce 5 condominium dwelling units on to a site having apartments each side, single family houses opposite, and residential development all around. The project will thus not create any new or unusual noise sources in the area. The project could generate up to 50 ADT on to Tamarack Avenue. This represents less than 1/2 percent of the total projected traffic flow on Tamarack Avenue and will be acoustically insig- nificant. NOISE IMPACT ON THE PROJECT Exterior Noise The buildings and associated paving will modify the sound field. The 65 dB(A) CNEL/Ldn contour will remain at a distance of 38 feet from the new centerline of Tamarack Avenue but, now using a hard ground propagation constant of 3 dB per doubling of distance, the future noise level at the face of unit 1 was calculated to be 62 dB(A) CNEL/ Ldn. The noise level on the east and west sides of James C. Berry - Acoustician Report No. 9110-R (619) 660-0064 Page 5 the Unit 1 building will drop by 3 dB(A) due to the 50 percent cut- off shielding of the structure. Thus, on both sides of the build- ing, the noise level everywhere will be below 60 dB(A) CNEL/Ldn. Units 2 through 5 will also all have noise levels below the requir- ed limit. At the north end of the building, there are stucco walls shielding the ground floor (see Figures 2 and 3). The noise level at ground floor level will be below 60 dB(A) CNEL/Ldn. The only part of the proposed building where noise levels will be above 60 dB(A) CNEL/ Ldn is the north face of the second story immediately overlooking Tamarack Avenue, where the noise level will be 62 dB(A) CNEL/Ldn (Unit No.l.) At all other walls, the exterior noise levels will be below 60 dB(A) CNEL/Ldn. At this elevation are the Living Room, Dining Room, Kitchen and Master Bedroom. There is a balcony overlooking the street (see Figure 3.) Interior Noise The noise reduction provided by typical Californian construction, i.e. wood framing, exterior stucco, interior drywall, R-ll insula- tion, and sliding glass doors and windows, is 25 to 30 dB(A) when all doors and windows are closed. (Source: County of San Diego Noise Element.) Thus, the noise level inside the living/dining room of Unit 1 will be in the range 31 to 36 dB(A) CNEL/Ldn, well in compliance with California Administrative Code, Title 24, and the City of Carlsbad requirements. MITIGATION Mitigation is required only at the balcony of Unit No.l. The ground floor is shielded by stucco walls. If the City staff feels it is necessary, the balcony requires shielding to the extent of 2 dB(A) on the north side. [It should be pointed out that the apart- ment buildings to the east (Nos.351 and 353 Tamarack Avenue) have balconies facing the street with NO acoustical shielding.] If mitigation is required, it is recommended that the north wall of the balcony deck (as indicated on Figures 2 and 3) be at least 5 feet high. The west wall can be left as shown in the drawing. Since view is important, consideration might be given to using glass or plexiglass for the balcony wall. No other mitigation is necessary. James C.Berry - Acoustician (619) 660-0064 Report No. 9110-R Page 6 SUMMARY Only a small portion of the site is currently impacted by noise levels in excess of 60 dB(A) CNEL/Ldn. Tamarack Avenue now car- ries 9,000 ADT which will rise to 9,700 ADT by buildout in the year 2010. A new alignment will move the centerline of Tamarack Avenue 10 feet closer to the site. The project will create significant but temporary construction noise. It will introduce no new or unusual noise sources into the area and the project-generated traffic noise will be acoustically insignificant. Only the north face of the second story of the building will have exterior noise levels above 60 dB(A) CNEL/Ldn, here the noise level will be 62 dB(A) CNEL/Ldn. Interior noise levels will be well below 45 dB(A) CNEL/Ldn with doors and windows closed. If mitigation is felt to be necessary, the balcony of Unit No.l should have a 5 foot high wall on the north side, which may be of glass or plexiglass in order to preserve the view. James C. Berry Acoustician