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HomeMy WebLinkAboutCT 89-22; BAYWALK; NOISE ANALYSIS; 1990-04-06NOISE ANALYSIS FOR BAYWALK TOWNHOMES CITY OF CARLSBAD, CALIFORNIA Prepared for GREGHEYDON 1301 DOVE STREET, SUITE 750 NEWPORT BEACH, CALIFORNIA 92660 Prepared by RECaJN Regional Environmental Consultants 1276 Morena Boulevard, San Diego, CA 92110-3815 275-3732 RECON NUMBER 2173N FEBRUARY 20, 1990 ----- TABLE OF CONTENTS ~ I. INTRODUCTIONANDSUMMARYOFFINDINGS 1 II. ME1HODSOFEVALUATION 1 III. IMPACTS 7 IV. MITIGATION 7 V. REFERENCES CITED 7 FIGURES 1: Proposed project location in relation to County of San Diego 2 2: Proposed project tentative map 3 3: Location of Interstate 5 cross section 5 4: Interstate 5 cross section 6 5: Future on-site Lctn noise contours 8 TABLES 1: Noise Model Input and Results for Interstate 5 9 2: Noise Model Input and Results for Chinquapin Avenue 10 3: Noise Model Input and Results for Harrison Street 11 P. 81 fEC(DN~egionaJ Environmental Consultants ~- JOB NUMBER: .,;>.;"75,J FAX TRANSMTITAL FAX N0.:. __ 4...:...· -=-3.-=B:;...-_,,:::;..0...,8'-1'-,'.fl--1 ______ _ FROM: Rn~/\/-&r:e-r ~ 1r//~ 3 DA TE: __ fl..,,,/4'-'-"i,;;;""•1--/2 .... «""o _____ _.TI..,..M,.,_,_,_E""": _ ,5;,:,o iC'k7 NUMBER OF P AGES: _ ___:$.=..____,.s::,;:._..::.. --,----,,-----,---- ( not including transmittal page) COMMENTS: RECON FAX NO. 619-275-3619 • 1276 Morena 601Jlevari: • S.a.n Oiego, CA s2i;c:-J81:5 • (t319) 275·3732 31~ Cnicago ~ • Riv011ic:t. CA 92S07 : (7141.~, •.0 Mr.Orqiffllycbi 1301 Do¥e Street.Suite 750 NllwptBea:11, CA 9Ui60 April 6, 1990 Ida...,.;. Mitigation to60 dBA far Baywalk TOWllllome.s (RECON Number 2173N) DearMr.Heydon; P,02 On ~ 3, 1990, I ieceived a Ill~ call from Mr. Cbrilller Westman of !be City of Carlsbad Community Dewlopmcal ~ concemmg die ooiae teclmical analysis prepared. for the proposed Baywalk Townhome.1. AB a follow-up to this te1ephooe conversation, I have COllducted funber Sllldies regarding the future ooise enviloameDt of die subject ,l&Vj)etl.Y, In die April 3 telepbon<: convl7Sfttioa, Mr. Wesllllall eitprcssed concern ovu ~ between lbe Day-N"igbt Average Sound Level (L.,) and lhe COlllllluoity Eqoivalent Noise Level (CNEl,). He also n:qnested Iba! RBCON provide addiliooa1 noise aoalySis of the subject pupeny ronsidering a (lO dBA residential noise uwimurn. The noise repo,t RECON pcpa,cd for tl>e iiUbject propeny (dated Fellraaty 20, 1990) lletennined nol$e impacu and mitigation in accoo1ance wilh a 65 dBA iesi<.lential noise llllllimum, lhe maximum indicaled in a zecent City Council meeting. I ~ to address lOOlt two issues, and telq,boned the resullS to Mr. Westmall lhe morning of April 4, 1990. My findings are summarized below: l. CNlil. ffl'BM L .. Scvml noise descripun wae used in die February 20, 1990, Baywalk To~ Noise Tecbnical Report, ioclucling dBA, L,.. and L..,. The basic mise mea.=ing scale is the A-weighted wund pressure level or dBA. wbicll approximates die frequency response of the hmnall em. Tho a:ilJOCiated ooiS<: levels are. widely oondrued wilh degrees of community impact and individual eff.cis. Three rommon r.cise rating scale.s use a modified A-weighted llOUDd level as a base. These are the L.,, L.., and CNEL. The Equn'8lent NoL<e Level or L.. Qlelbod is au &Vfft8e ooise level based 011 the avenl8e eiierg,i, CO!lltDt of soaoo and is the basis fca­ bOdl the L.., and the CNEL. TIie L• and CNEL noise rating scales rn<W.Jre the cumuLltive DOise e>.pOS~ in a ccmrnuoity by summing the hourly L., over a 24-hour time period and awlyltlg an incmised weigh tng factor to eveuingfnighaime hours. In die ~ of L..,, daytime is ~ as 7:00 a.111. to 10:00 p.m and night• lime is defined as 10:00 p.m. to 7:00 a.m. A 10 decibel )lffialcy is assignoo ID llig!mime noise i11 the L .. scale. The CNEL scale is similar to the L.., scale; lk,,wever, day is defiMd as 7:00 am. ro 7iJO p.m~ evening is defined as 7:00 p,m. to 10:00, and nighlliroe is defillt:4 as j(};()() pm 10 ~:00 a.m. In the CNEL si:ale, a five deallel penalty is as.sigi,ed to evening ho=, and a ten decibel penalty is assigned to Digbaime hours. The noise scale used in !be UCON repon was L... RecalcolatiOIJ of prediaed ~ L., v'8lues affotds represeotalive CNllL values for comparison. Re.suits show a diffmnce of betwffll four -!"'1ths and she11- telllhs decibel, with CNEL being hlgba-. The L. wJues shown in the Febnla!y 20, 1990, report were figures row:ided from two decimal places. Addition of ~,;;:n foar-tenths aDd ~-temlls dea'bel to the unrounded fi&mes does not 1"Uh in subsranlial noise level difft't'ene4'S, In short, L• and CNEL values wete ~ in this case, to be ~Y Ille same. 1278 M01ena BoukMlnl • San o,ogo, CA gi,,1().3815 • (">8) 275-3732 • MX (8'1,I) 275-3619 511118 Eaal Gnlnt Road, Sull8 301A • Tucson, AZ.115712 • (802) 32!>-9977 3050 Chicago,_,.,. • l'Mrslde, CII 92507 • (714} ,..,: .) -2- 2. Mlda!lm !Q@dBA I . ! April 6, l!IM ! ••. •. • • · . . ii I . I Pftdiclecl lillure noise levels at five feet inside the property line, six feet above finished flo«, ~ oot mad 10 ~ 60 dBA OYet most c. the pmpeny. Along Chinqllapin Avenue, in the nonh and 1 IIOrtllwea portion of tbe subject property, however, Ille 60 dBA conrour was fowid to oocur bei.ween 20 and 35 feet i.aside the P,opetly line. Tim hlformatioo is contained in die Febn8y 20, 1990, noise teebAA;al report. In Cllder IO redqce fumle exterior llllise to a level equal to or below 60 dBA, a minimulll four-Coot­ hip noise lxurier would need IO be OOIISUIICle:I between the llOise aoun;e aad the fulull: ~-The. balllolll of dlis bmTier should be at a ground surface devadai equal IO !bat of die future iesidences; i.e., the baricr is assumed to be placed at ar lle8f lhe edge of !be flat. buildablt'/yard area {between tbe fumle ~ and ChiPquapia Avenue). Oive11 a 60 dBA !Uidemial mwmum, one example of rniligaliori would be ro place a four-foot-high noise wall along lhe nonh property booodary and Olinquapin right.of• way, meoding ll'QUOd the comer of Clwlquapin Aveau.e and Hamson Sueet, and along Harrison Street fur apfJIOximaldy 30 feet from the apex of the CQmer. This would reduce exterior noise levels IO below 60 dBA for flllUr9 ~ five feel inside the property. A suirable alU:rnalive, as offered by Mr. Westrnao, would be to place a millimWII four-foot-high noise barrier 10 or lS feet inside tbe Jlrtlpeny llne along Ille ll0dbati boomdary (pamllel IO die pn>jecl planned zero to two and -.half.foot bigh mainiog wall), IO yWd fupn-o ooue !&vets below 60 dBA tm lbe yard area and midenceJ SOUlh ri die barrier. lD this ca. lbe noise barrier would also need IO extend around lhe comet of Chinquapio Avenue and Harrison Slrffl. Sbould you have aoy queslioos. pleue c:aD. KLB:db ~ Cbrisret Westman L • L INTRODUCTION AND SUMMARY OF FINDINGS The site of the proposed Baywalk Townhomes is located generally east of Interstate 5 (1-5) and north of Batiquitos Lagoon in the southern portion of the city of Carlsbad (Figure 1). The west property line of the 2.5-acre site occurs approximately 310 feet east of 1-5. The site occurs within a larger, relatively flat "mesa" existing at an average height of thirty-five feet above I-5. The top of the slope lies approximately 100 feet east of the freeway. The west property line, therefore, is roughly 210 feet east of the top edge of the slope paralleling I-5. Due to a row of existing two-and three-story apartment buildings north and west of the property, I-5 is not visible from the project site. Local residential streets Chinquapin Avenue, Harrison Street, and Locust Street form the property's north, west, and south limits (Figure 2). Implementation of the project would not require a change in the existing R-2 zone. A total of 28 multiple-family dwelling units are proposed over the 2.5- acre site, resulting in a density of 11.2 dwellings per acre. All units would be two stories and would have second-floor balconies. The acceptable noise level established by the City of Carlsbad for residen­ tial development is 65 A-weighted decibels Community Noise Equivalent Level (dBA CNEL) at a point five feet inside the proposed project's property line at six feet above finished grade level, and immediately above the highest window or door opening in a dwelling unit (Holzmiller, City of Carlsbad, 2/13/90). Future on-site noise levels expected to be generated from vehicular traffic on surrounding roadways were determined in this noise study not to breach the 65 dBA CNEL City of Carlsbad residential noise standard. Further, over most of the site, noise levels would not exceed 60 dBA CNEL. This is important to note because past discussion within the City of Carlsbad favored a 60 dBA CNEL maxi­ mum for residential areas. On-site noise levels are not anticipated to be significant due largely to the shielding effects provided by the adjacent two-and three-story apartment buildings to the north and west. Noise attenuation due to shielding is an important mechanism by which roadway sound levels are lowered. Shielding occurs when the observer's view of the roadway is partially or wholly obstructed by an object or objects which significantly interfere with the propagation of sound waves. Five decibels of attenuation is provided by a row of buildings which occupy 65 to 90 percent of the length of the row (FHW A Noise Prediction Model Manual 1978:32). The aforementioned apartment buildings occupy roughly 80 percent of the length of the row. Approximately 224 vehicles per day are anticipated to be generated by the proposed project. This would not result in a significant contribution to the noise level in the area. IL ME1HODS OF EVALUATION The noise scale used in this study is Lc1n, which is a 24-hour, time-weighted annual average noise level based on the A-weighted decibel. A weighting is a frequency correction that correlates sound pressure levels with the frequency response of the human ear. Time weighting involves the addition of 10 dBA to the average noise levels (Leq) between 10:00 p.m. and 7:00 a.m. The nighttime period is weighted to account for added sensitivity to noise during this time 1 ;() • Fallbrook I RIVERSIDE COUNTY --+--------~---- • Borrego Ocolillo Wells ....J < 'ii: w Q. :::!: FIGURE 1. THE LOCATION OF THE PROPOSED PROJECT RELATIVE TO THE COUNTY OF SAN DIEGO . ._ .... ------------------------------------.-.---------------------------------------.-.-.-----.--;.--~ -------------~-----------.-.-.-.---------.-.-.-.-.-.-.-.-.-.-.-.---.-.-.-.-.-.-.--;.---REC!DN ;;;;;;;;;;~. PROJECT BOUNDARY 45 feet s: IT "' ,0 I ' ri1 ~ m ,<. t X ~ "t j: ~ ! ,. ~ i\ ~ i < r, r f iii 1 ! FIGURE 2. BA YWALK TOWN HOMES VESTING TENTATIVE MAP • • period. For practical purposes, agreement of Lc1n and CNEL are so close that the Lc1n values used in this study may be considered equivalent to the CNEL values used in the City's noise standards. An Lc1n of 65 dBA was used as the threshold criteria for the critical level of noise affecting development of the subject property, since it is the noise level considered compatible with residential areas by City of Carlsbad (Holzmiller, City of Carlsbad, 2/13/90). Based on the Carlsbad Planning Department's Policy Number 17, the required locations for noise receptors are: . 1. Five feet inside the proposed project's property line at six feet above finished grade level, and 2. Immediately above the highest window or door opening in a dwelling unit. For this analy~is, noise levels were calculated for points five feet inside the project boundary at a height six feet above the proposed finished floor elevation, and at 15 feet inside the project boundary at a height of 16 feet above the finished floor (Figure 3). The latter point represents a second­ story window or door opening in the buildings set back 15 feet from the property line. Future noise levels were determined by modeling 1-5, Chinquapin Avenue, and Harrison Street for future traffic conditions using the Federal Highway Admin­ istration noise model (FHW A 1978). The model requires as input the projected . roadway average daily traffic (ADT), roadway gradient, vehicle speed, and vehi­ cle mix, the percent of total vehicles consisting of automobiles, medium trucks, and heavy trucks. The segment of 1-5 nearest the property is an eight-lane freeway, with the northbound travel lanes approximately 310 feet from the west property line. Caltrans predicts a projected ADT of 205,000 for 1-5, year 2010, and a mix of 93 percent automobiles, 3 percent medium trucks, and 4 percent heavy trucks, (Max Wickam, Caltrans District 11, 12/14/90). A vehicle speed of 55 miles per hour was considered typical for this section of 1-5. Chinquapin A venue, Harrison Street, and Locust Street are all local resi­ dential streets intended to serve abutting lots, not carry through traffic. Locust Street, which would serve only the project and adjacent property, would not likely carry a volume of traffic large enough to contribute measurably to other roadway traffic noise. Harrison Street would provide access to the proposed project and the several adjacent existing apartment buildings. An ultimate ADT of 2,200 on Harrison Street is considered conservative, and is based on accepted street design standards. Chinquapin Avenue would expect to carry a slightly higher volume of traffic due to its juxtaposition between the less frequented local streets and the larger residential collector streets. A future ADT of 5,000 for Chinquapin Avenue was used .to determine its noise contribution. The percent vehicle mix for these local streets is estimated to be 99 percent autos, 0.5 percent medium trucks, and 0.5 heavy trucks. The FHW A noise model also talces into account the effect of topographic variation between the noise source and potential noise receptor. To this end, a representative cross section was drawn from a given receptor perpendicular to the centerline of the roadways. Figure 4 shows the cross section drawn for 1-5. (Refer to Figure 3 for cross section location.) Topography between the west 4 ' 1· i ~~it~ ./'-'il.c-;~-~~~~~~.;:;:~~~Zd~H~ ·-.. w •• i j l,, • i j ! ! -, Lo% Ml' ·,~.~~~~ .............. =--' ---- i .• .. -i PROJECT BOUNDARY] 0 45 If. -· ,__. feet ~ i m )(. j; ~ ! 1 II .. < ~. !=' i-t ;Ii 1 ! ~~ r, "' ~ I ' IT ~ 1(. t: ~ :t ,. t ~ I I l ' ~ '!'-'· ..... ~ ~8 I FIGURE 3. -:+~__j_~ CROSS SECTION AND RECEPTOR LOCATIONS USED IN NOISE MODELING to A' Receptor I Receptor II • • A Ci R/W R/W Harrison St. West Property line R/W 1-5 R/W 0 100 feet FIGURE 4. CROSS SECTION MODELING INTERSTATE 5 • ' perimeter of the site and the centerline of I-5 was obtained from County 200' scale orthophoto maps. Generally flat topography exists between Harrison Street, Chinquapin Avenue, and the property; drawings are therefore not included in this report. The equivalent lane distance method was used for the placement of the noise source, barriers, and receptors in the noise model. The equivalent lane distance (ELD) is equal to the square root of the product of the distance to the near lane (DNT) and the distance to the far lane <DFr,). The near lane distance is measured ·from the edge of the right-of-way to the center of the near lane; the far lane distance is the distance from the edge of the right-of-way to the center of the far lane. I-5 in the vicinity of the project consists of eight travel lanes, an approximate 40-foot-wide planted divider, and attendant eight­ foot-wide shoulders, all occurring within a 200-foot right-of-way. The resulting calculated Om,, Dpi,, and ELD are 34 feet, 166 feet, and 75 feet, respectively. Based on a 40-foot pavement and 60-foot right-of-way, the Om., Dpi,, and ELD for Harrison Street and Chinquapin Avenue are calculated to be· 24 feet, 36 feet, and 29 feet, respectively. · A contour map of future Ldn noise levels on the project site is shown in Figure 5. The graded topography shown on the site plan, as well as the shielding effect of multi-family residences between the subject property and the noise sources are reflected in the contours. The contours also reflect the summation of the separate noise sources (three separate roadways). The noise model input parameters and output results are shown in Tables 1, 2, and 3. ill. IMPACTS The noise level impact on the ground floor near the property line can be determined from Figure 5. The noise levels are shown to be in the range of 63 dBA to 50 dBA. The second-story noise levels are approximately the same as the first-story when separately considering noise from Chinquapin Avenue and Harrison Street. The second-story noise levels are slightly higher than the first-floor when considering noise from I-5. Adding all three roadway's calcu­ lated second-story noise values where appropriate, second-story noise levels could attain 64 or 65 dBA Ldn. IV. MITIGATION The results of this noise study indicate that future residences of the proposed Baywalk Townhomes project would not be exposed to noise values greater than the City of Carlsbad 65 dBA CNEL residential noise maximum. V. REFERENCES CITED Carlsbad, City of 1988 Planning Department Administrative Policy Number 17. December 6. Federal Highway Administration 1978 Highway Traffic Noise Prediction Model. Report No. FHWA-RD-77-108. U.S. Department of Transportation, Washington, D.C. February. 7 7 ·I ....... 1 i ··,1 ' ' ----__ ,,,_, . ~TR FIGURE 5. FUTURE Ldn NOISE CONTOURS 0 45 feet A. B. C. • • TABLE 1 FHW A TRAFFIC NOISE MODEL -INPUT/OUTPUT DATA FOR INTERSTATE 5 YEAR 2010 BAYWALK IDWN HOMES SOURCEDATA Classification Freeway R-0-W Width 200 Near Lane Dist. 34 Far lane Dist. 166 F.quivalent Lane Distance 7 5 ADT 205,000 Distribution: Auto 93% Medium Truck 3% Heavy Trucks 4% Speed 55mph RRCEPTOR DATA-INPUT Cross section 1 2 Angles -87,87 -87,87 Source-to-slope top 189 189 Slope top-to-receptor 215 230 Slope top height 35 35 Receptor height 6 6 Second receptor height 16 16 Site conditions A A Grade 1% 1% OUTPUT Receptor;ti 56 56 -5 dBA for hielding 51 51 Second receptor 1m 58 58 -5 dBA for Shielding 53 53 NOTES: Receptor 1 is placed 5 feet within the west property line. Receptor 2 is placed 15 feet within the west property line. All distances are specified in feet; all noise levels are specified in dBA. Slope top and receptor heights are relative to roadway. A = absorptive site. Ground-floor receptors placed 6 feet above ground simulate average height of human ear. • TABLE2 FHWA TRAFFIC NOISE MODEL -INPUT/OUTPUT DATA FOR CHINQUAPIN A VENUE BAYWALK 10WN HOMES A. SOURCE DATA Classification Local Residential Street R-0-W Width 60 Near Lane Dist. 24 Far lane Dist. 36 Equivalent Lane Distance 29 ADT 5,000 Distribution: Auto 99% Medium Truck 0.5% Heavy Trucks 0.5% Speed 30mph B. RECBPTQR DATA-INPUT Angles Source-to-receptor I Receptor I-to-n:ceptor n First-floor receptor ht. Second-floor n:ceptor ht. Site conditions Grade C. OUTPUT First-floor Receptor Lm. Second-floor n:ceptor Lc1n Lcm=65,Distance Lcm=60,Distance Reference Cross-Section -87,87 29 5 6 16 R 0.5% 62 62 20 Withl-5 and Harrison St. Added 63 63 35 NOTES: All distances are specified in feet; all noise levels are specified in dBA Lc1n, R = reflective site. Ground-floor receptors placed six feet above ground simulate average height of human ear. Lc1n = 65 dBA and 60 dBA distances are measured from the property line. • TABLE3 FHWA TRAFFIC NOISE MODEL-INPUT/OUTPUT DATA FOR HARRISONSTREET BAYWALK 10WN HOMES A SOURCEDATA Classification Local Residential Street R-0-W Width 60 Near Lane Dist. 24 Far lane Dist. 36 Equivalent Lane Distance 29 ADT 2,200 Distribution: Auto 99% Medium Truck 0.5% Heavy Trucks 0.5% Speed 30mph B. RECEPTOR DATA -INPUT Angles Source-to-receptor I Receptor I-to-receptor n First-floor receptor ht. Second-floor receptor ht. Site conditions Grade C. OUTPUT First-floor Receptor Ldn Second-floor receptor Ldn Lcm=65,Distance Lcm=60, Distance Reference Cross-Section -87,87 29 0.5% 5 6 16 R 56 56 With 1-5 and Harrison St. Added 59 59 NOTES: All distances are specified in feet; all noise levels are specified in dBA Ldn. R = reflective site. Ground-floor receptors placed six feet above ground simulate average height of human ear. Ldn = 65 dBA and 60 dBA distances are measured from the property line.