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Home My WebLink AboutCT 99-14; The Regency; Tentative Map (CT) (17)^ Investigative Science and Engineering 3511 Cam/no Del Rio South, Suite 302 Phone/Fax: 619-640-9379/619-640-0763 San Diego, CA 92108-4003 www.ise-advantage.com July 12, 1999 Mr. Martell B. Montgomery La Costa Engineering 2382 Camino Vida Roble, Suite L Carlsbad, CA 92009 Re: Brett Development, Inc. Regency Property Acoustical Study (ISE Report #99-030) Dear Mr. Montgomery: At the request of La Costa Engineering, Investigative Science and Engineering (ISE) was directed to investigate potential noise impacts to the proposed Brett Development, Inc. Regency Property residential development located in Carlsbad, California. An acoustical survey of the site was performed on June 9, 1999. The results of that survey, as well as predicted future sound levels at the site, are presented in this letter report. Introduction and Definitions Existing Site Characterization The proposed development consists of 1.77 acres (gross) located within the City of Carlsbad, San Diego County (APN's 215-360-16,17,18). The site is nestled within a residential community, which is bordered to the north by Unicornio Street and to the south by Alga Road (refer to Figure 1). Surrounding land uses to the west and east includes multi-family housing. A single-family housing development is located adjacent to the north of the project area. Site survey photographs are provided in Attachment A of this report. The planned development requests the construction of 12 lots (11 + Common Area) to be built within a residentially zoned (RD-M) neighborhood at a proposed density of 6.2 units per acre. The City's designated General Plan Land Use is RMH. The existing topography of the site has been cleared and graded; however, not to final pad elevations. The adjacent roadway to the south (Alga Road) is at an elevation approximately 30 feet above the proposed lots. Elevations on site range from approximately 480 feet above mean sea level (MSL) at Lot # 12 to approximately 490 feet MSL at the proposed Common Area (refer to Figure 2). Mr. Martell B. MontgoriWf Brett Development, Inc. Regency Property Acoustical Study ISE Report #98-030 July 12, 1999 Page 2 Figure 1: Project Vicinity Map (Thomas Guide Page 1127, Grid B5) Acoustical Definitions Noise is generally defined as unwanted or annoying sound that is typically associated with human activity and which interferes with or disrupts normal activities. Although exposure to high noise levels has been demonstrated to cause hearing loss, the principal human response to environmental noise is annoyance. The response of individuals to similar noise events is diverse and influenced by the type of noise, the perceived importance of the noise and its appropriateness in the setting, the time of day, and the sensitivity of the individual hearing the sound. Airborne sound is a rapid fluctuation of air pressure above and below atmospheric levels. The loudest sounds the human ear can hear conformably is approximately one trillion (a one with 12 zeros following it) times the acoustic energy that the ear can barely detect. Because of this vast range, any attempt to represent the acoustic intensity of a particular sound on a linear scale becomes unwieldy. As a result of this, a logarithmic ratio known as the decibel (dB) is commonly employed. A sound level of zero "0" dB is scaled such that it is defined as the threshold of human hearing and would be barely audible to a human of normal hearing under extremely quiet listening conditions and would correspond to a sound pressure level equal to the reference level. Mr. Martell B. MontgonW* Brett Development, Inc. Regency Property Acoustical Study ISE Report #98-030 July 12, 1999 PageS Figure 2: Project Area Topography (USGS 7.5 Encinitas Quadrangle 1:12000) Most of the sounds we hear in the environment do not consist of a single frequency, but rather a broad band of frequencies differing in sound level. The intensities of each frequency add to generate the sound we hear. The method commonly used to quantify environmental sounds consists of determining all of the frequencies of a sound according to a weighting system that reflects the nonlinear response characteristics of the human ear. This is called "A" weighting, and the decibel level measured is called the A-weighted sound level (or dBA). In practice, the level of a noise source is conveniently measured using a sound level meter that includes a filter corresponding to the dBA curve. Although the A-weighted sound level may adequately indicate the level of environmental noise at any instant in time, community noise levels vary continuously. Most environmental noise includes a conglomeration of sounds from distant sources that create a relatively steady background noise in which no particular source is identifiable. For this type of noise a single descriptor called the Leq (or equivalent sound level) is used. Leq is the energy-mean A-weighted sound level during a measured time interval. It is the 'equivalent' constant sound level that would have to be produced by a given source to equal the fluctuating level measured. For most acoustical studies, the monitoring interval is generally taken as one-hour and is abbreviated as Leq-h. f"S Mr. Martell B. Montgom^ Brett Development, Inc. Regency Property Acoustical Study ISE Report #98-030 July 12, 1999 Page 4 To describe time-varying character of environmental noise, the statistical noise descriptors L10, L50, and L90 are commonly used. They are the noise levels equaled or exceeded during 10 percent, 50 percent, and 90 percent of a stated time. Sound levels associated with the L10 typically describe transient or short-term events, while levels associated with the L90 describe the steady state (or most prevalent) noise conditions. In addition, it is often desirable to know the acoustic range of the noise source being measured. This is accomplished through the maximum and minimum measured sound level (Lmax and Lmin) indicators. The Lmin value obtained for a particular monitoring location is often called the acoustic floor tor that location. Another sound measure employed by the State of California (and adopted by the City of Carlsbad) is known as the Community Noise Equivalence Level (or CNEL) is defined as the "A" weighted average sound level for a 24-hour day. It is calculated by adding a 5 decibel penalty to sound levels in the evening (7:00 p.m. to 10:00 p.m.), and a 10 decibel penalty to sound levels in the night (10:00 p.m. to 7:00 a.m.) to compensate for the increased sensitivity to noise during the quieter evening and nighttime hours. Applicable Significance Criteria City of Carlsbad The Noise Element of the City of Carlsbad identifies sound levels that are compatible with various land uses. According to the City of Carlsbad Draft Noise Guidelines Manual, sound levels up to 60 dBA CNEL are compatible with residential land uses. Sound levels up to 65 dBA CNEL are compatible with recreational areas such as parks and playgrounds. The City also requires an interior noise study (compliant with State of California CCR Title 24 standards) where exterior exposure is in excess of the above land use criteria. Rear and side yard areas of the proposed Brett Development, Inc. Regency Property residential development would be classified as usable exterior living space; thus, the City's guidelines will be applied in this report to determine the requirement of exterior and interior mitigation at all proposed units within the development adjacent to Alga Road and Unicomio Street. State of California CCR Title 24 The California Code of Regulations (CCR), Title 24, Noise Insulation Standards, states that single- and multi-family dwellings, hotels, and motels located where the CNEL exceeds 60 dBA, must obtain an acoustical analysis showing that the proposed design will limit interior noise to less than 45 dBA CNEL. Worst case noise levels, either existing or future, must be used for this determination. Future noise levels must be predicted at least ten years from the time of building permit application. The City of Carlsbad has adopted the CCR Title 24 standards. *>«\ '•'">. Mr. Martell B. Montgorfwy "*** Brett Development, Inc. Regency Property Acoustical Study ISE Report #98-030 July 12, 1999 PageS Analysis Methodology Existing Conditions Field Survey Two Larson Davis Model 700 ANSI Type 2 Integrating Sound Level Meters were used as the data collection devices. The meters were placed at 1) along Unicomio Street correlating to proposed Lot # 5 (ML 1); and 2) the location of proposed Lot #8, adjacent to Alga Road (ML 2). All meters were mounted on tripods roughly 5 feet above the ground in order to simulate the average height of the human ear above ground. The measurements were performed on June 6, 1999. The sound level meters were calibrated before and after each set of measurements. Future Acoustical Environment Modeling The Caltrans Sound 32 Traffic Noise Prediction Model with California (CALVENO) noise emission factors (based on FHWA RD-77-108 and FHWA/CA/TL- 87/03 standards) was used to calculate future onsite vehicular traffic noise levels. Model input included a digitized representation of the alignment of Alga Road and Unicomio Street, as well as any local site topography, future ADT volume, vehicle mix, and receptor elevations. The roadway and site topography elevations were obtained from the project site plan (Source: Brett Development Inc. Regency Property TM - La Costa Engineering - 5-4-99). Model output consisted of peak hour energy-mean A- weighted sound levels (or Leq-h) for each receptor examined. Receptor elevations were considered to be 5 feet above the appropriate floor (pad) elevation. The model assumed a "hard" site sound propagation rule (i.e., a 3-dBA loss per doubling of distance from roadway to receiver) in accordance with Caltrans practices. The model also considered the attenuation due to the slope adjacent to the project site. Future noise levels were calculated for the first and second floor elevations (assumed to be five and 20 feet respectively above the building pad). Findings Ambient Sound Measurement Results Testing conditions during the monitoring period were sunny and clear with an average barometric pressure reading of 29.95 in-Hg, an average northerly wind speed of 3 to 5 miles per hour (MPH), and an approximate mean temperature of 79 degrees Fahrenheit. The results of the sound level monitoring are shown below in Table 1. The values for the energy equivalent sound level (Leq), the maximum and minimum measured sound levels (Lmax and Lmin), and the statistical indicators L10, L50, and L90, are given for each monitoring location. Measurements collected at monitoring locations ML 1 and ML 2 reflect typical sound levels associated with the community setting observed and the topography of the surrounding terrain. The onsite hourly energy average sound levels (or Leq-h) /*"•*• Mr. Martell B. MontgonW^ •—' Brett Development, Inc. Regency Property Acoustical Study ISE Report #98-030 July 12, 1999 Page6 recorded at ML 1 and ML 2 was constant throughout the duration of the monitoring period. As indicated by the monitoring equipment, at least 90 percent of the time the onsite sound level averaged between 43.5 and 44.0 dBA. The difference between the Leq and L90 metrics was directly attributable to the intermittent nature of automobile traffic along Alga Road during afternoon peak hour conditions. The acoustic floor for the site, as seen by the Lmin indicator was low (between 38.5 and 40.5 dBA for all locations monitored) and reflects the semi-rural community noise environment of the project site. Table 1: Measured Ambient Sound Levels - Brett Development, Inc. Regency Property Site ML ML 1 2 Start 3:00 3:00 Time P P m. m. 1 -Hour Noise Level Leq 53.1 52.3 Lmax 68 70 5 5 Lmin 38.5 40.5 Descriptors in dBA L10 56.0 55.0 L50 50.0 49.0 L90 43.5 44.0 Monitoring Locations: «> ML 1: Meter positioned along Unicornio Street (Lot #5) GPS 33°06.595'N x 117°14.487'W * ML 2: Meter positioned adjacent Alga Road (Lot #8) GPS 33°06.568'N x 117°14.483'W Measurements performed by ISE on June 6,1999. Future Traffic Noise Impacts The primary source of future traffic noise in the vicinity of the project would be from Alga Road. Future year 2010 volume along this roadway alignment is projected to be 11,000 ADT traveling at the posted speed of 50 MPH (Source: SANDAG Series 8 Model Projections). The projected year 2010 ADT for adjacent Unicornio Street is below the level of analysis for the traffic model and thus was taken as 1,000 vehicles with a posted speed of 25 MPH. Peak hour traffic values are calculated for an 8% traffic flow pattern and a 98/1/1 (automobiles/medium/heavy vehicles) percent mix in accordance with Caltrans traffic forecasting practices. For peak hour traffic percentages between approximately 8 and 12 percent (and a Level of Service, or LOS, between A through C) the energy- mean A-weighted sound level is equivalent to the 24-hour Community Noise Equivalent Level (CNEL). Outside this range, a maximum variance of up to 2 dBA occurs between Leq-h and CNEL. ^>V Mr. Martell B. Montgorrk^ Brett Development, Inc. Regency Property Acoustical Study ISE Report #98-030 July 12, 1999 Page 7 The results of the acoustical modeling are shown below in Table 2. Values for selected pad locations adjacent to Unicornio Street and Alga Road are given. Also shown are the predicted noise levels for 1) unmitigated ground floor areas, and 2) unmitigated second floor levels. Based on the model results, no exterior traffic-related noise impacts were identified. Second floor areas of units constructed upon Lots #8 and #9 would require interior noise mitigation per CCR Title 24 standards. The interior acoustical analysis should be completed prior to submission of final architectural designs for the proposed units situated on the affected pads. Table 2: Acoustical Modeling Results of Representative Lots - Brett Development, Inc. Regency Property Receptor Location Common Area 2 3 4 5 6 7 8 9 10 11 12 Ground Level Areas 56.2 56.9 55.9 55.8 56.1 55.8 55.4 54.9 57.1 57.3 56.1 56.3 Second Floor Areas 59.5 58.8 57.3 56.7 56.9 57.2 58.4 60.0 (I) 60.4 (I) 59.0 57.1 56.7 Notes: * Modeled using the Caltrans Sound 32 Traffic Noise Prediction Model with California (CALVENO) noise emission factors (based on FHWA RD-77-108 and FHWA/CA/TL-87/03 standards). * Levels denoted with (I) indicates the requirement of interior noise mitigation. * All sound levels given in dBA CNEL. Mr. Martell B. Montgomk*/ Brett Development, Inc. Regency Property Acoustical Study ISE Report #98-030 July 12, 1999 Page8 Aircraft Transportation Noise Sources Identified The project site lies outside the influence areas of McClellan-Palomar Airport and associated industrial uses. The airport is currently operating at full capacity (maximum typical number of flight operations per day) and no appreciable increase in the contours is expected within the project analysis horizon. Thus, no significant impacts to the project site due to aircraft operations are expected. Conclusions Future exterior noise levels for units located within the Brett Development, Inc. Regency Property were found to be below the 60-dBA CNEL threshold established by the City. Second floor areas of units constructed upon Lots #8 and #9 would require interior mitigation measures to reduce impacts to below a level of significance. The interior acoustical analysis should be completed prior to submission of final architectural designs for the proposed units situated on the affected pads identified in Table 2 above. Should you have any questions regarding the above conclusions, please do not hesitate to contact me at (619) 640-9379. Sincerely, Rick Tavares, REA, INCE Project Principal Investigative Science and Engineering Cc: Glen Laube, ISE Attachments: Attachment A - Site Survey Photos Attachment A - Fiel^urvey Photos Figure A1: Project Site Looking Northwest Attachment A - Fieldwirvey Photos Figure A2: Project Site Looking Northeast Attachment A - FieHWurvey Photos „,*<** n*. *«*- -SB- * "* " ™ **, *** "*^ **«* ,""^«*T*^ "y*.1 ^sj-^^Xj •>- at " "• 4 3W -^*- "tj*4,> » r**... ^^m j»" --"•- ^-i^m- % "*?*•«•• «•*> «sa«! "--%» " "J('^'*«i'v*«W^- •r^-^\ ^f:- -jf^r^i>>-<• Figure A3: Project Site Looking East Attachment A - FieloS^rvey Photos Figure A4: Alga Road Looking East Attachment A - Fiel&».#tirvey Photos \S?t-i5-vj".'Sv- J"<"- -' ••-•' *" ~ s^'*&€t^./;\ w< •s. Figure AS: Unicornio Street Looking East r*Attachment A - Field\»*rvey Photos Figure A6: Monitoring Location ML 1 Attachment A - Fiel^efurvey Photos Figure A7: Monitoring Location ML 2