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HomeMy WebLinkAbout12/05/2000, C3 - RESIDENTIAL SOUNDPROOFING council M° ° s j Ac en 6A REpoRt 'Q C I TY OF SAN LU IS O B I S P 0 FROM: Mike McCluskey,Director of Public Works`1&110* ' Prepared By: Keith Opalewski,Parking Manager SUBJECT: RESIDENTIAL SOUNDPROOFING CAO RECOMMENDATION Approve expenditure of $31,611 from the Parking Fund's completed Capital Improvement Project (CIP) account to soundproof the apartment building at 865 Morro Street (Berkemeyer Apartments) as a condition of the approved mitigation measures for the construction of the Palm Street Parking Garage. DISCUSSION Background In 1986 an initial environmental impact study was completed as part of the approval process for the construction of the Palm Street Parking Garage. The project was granted a negative declaration with approved measures (Attachment 1) to mitigate potential adverse environmental impacts for the garage construction. One of these measures required"some means of minimizing noise to the adjacent apartment shall be provided..." to insure compliance with the city's noise standards. It was anticipated that the operation of the new garage would increase ambient noise levels that could exceed the city's noise standard (above 60 decibels-dB) for residential areas. The suggested means for providing soundproofing was the installation of dual-pane windows and/or construction of a noise barrier between the garage and the adjacent apartment building. Although the garage was completed in 1987, no formal soundproofing measure was ever completed for the adjoining apartment building. The exact reason(s) for this is uncertain due to the time that has lapsed since the garage was built. However, since there was no formal environmental impact report completed for the garage, no official mitigation monitoring and reporting program was adopted for this project Moreover, this lack of any formal action is reinforced by the fact it was the city's first garage with an unknown noise impact to the adjacent apartment building, so initially nothing was done to soundproof the building. Over the years there has been an increased use of the Palm Garage, especially on Thursday, Friday and Saturday evenings. This increased activity has resulted in an intensification of noise that has been impacting the residents of the adjacent apartment building. This escalation has prompted the current owner of the building to request that the City fulfill the intent of the 1986 mitigation measure to provide some soundproofing to the apartment building. The owner has requested that 88 dual-pane windows be provided to insure that the noise levels do not exceed city standards. CM Council Agenda Report—Residential Soundproofing Page 2 Noise Analysis Since it has been 13 years since the garage was completed, staff commissioned a sound consultant (Krause Engineering Services) to ascertain the current noise levels associated with the operation of the garage. Field surveys were conducted over a four-day period (Thursday- Sunday) at various times of the day and night in order to assess typical noise exposure at various times of the week. The survey included measurements during Farmer's Market, late night on Friday and Saturday, and midday Saturday. Maximum and minimum sound levels were determined for the survey period, along with average sound levels for the entire survey period. The results are summarized below and detailed on Attachment 2. Minimum levels ranged from 48 to 53dB (decibels) Maximum levels ranged from 60 to 75dB* * The higher levels were typically short durations (1-3 minutes) from car alarms Average noise levels were calculated at 59dB Day-Night Average Sound Level (Ldn) Based on the city's current noise standard, which allows a maximum of 60dB Ldn, the consultant concluded that no formal mitigation was required because existing average sound levels technically did not exceed city standards. The property owner was provided a copy of the sound study and informed that although the findings technically did not warrant any sound mitigation, we would agree to soundproof the rear of the building (25 windows) as a good faith effort because the decibel levels were close to the maximum allowed. The property owner felt the offer was insufficient because other portions of the building were affected by the spikes in decibel levels from car alarms, loud music, engine noise, and groups of users coming and going from the garage. As a result, the owner commissioned his own independent sound engineer (David Dubbink Associates) to evaluate the city's noise study and recommendations. The analysis and additional field measurements conducted by Dubbink (Attachment 3) supported the findings of the city's noise study for typical decibel levels. However, in a worst-case scenario set up by the consultant for car alarms, noise levels exceeded city standards. This same finding was reflected in the city's study, which clearly indicated spikes of up to 75dB. Thus, both studies supported the average sound levels are within established noise standards,but that the "sound spikes" clearly exceeded the 60dB level set forth in the noise ordinance. Considering the magnitude of the sound spikes, and the city's obligation to provide some soundproofing pursuant to the 1986 mitigation measure, staff had the city's consultant reevaluate all of the pertinent data. Since the average levels were so close to the maximum (59dB vs. 60 dB), and the sound spikes exceeded levels by up to 15dB (750), our consultant submitted a revised recommendation for soundproofing the building. The window replacement schedule (Attachment 4) recommends 65 windows replaced along the south and west faces of the building including the south face of the courtyard. An additional 11 windows on the north face of the courtyard were not recommended on technical grounds, but could be considered to provide a more extensive sound buffer zone. The 65-window proposal was presented to the property C3-2 Council Agenda Report–Residential Soundproofing Page 3 owner who felt the additional 11 windows should be included in the final number. After discussing the sound reflection potential within the courtyard area, staff agreed that the 76 windows would be a more comprehensive soundproofing of the building. The owner accepted this proposal. When all of the factors are considered (time delay, increased use, high spike levels, close proximity to the entrance/exit lane, and the city's legal obligation to mitigate noise) the recommended proposal of replacing 76 windows to improve the quality of life for nearby apartment residents is a fair and reasonable offer. CONCURRENCES The City Attorney's Office has reviewed all aspects of this request/requirement to provide some means of soundproofing for the apartment building and supports the final recommendation for window replacement. FISCAL IMPACT The recommended proposal to provide 76 dual-pane windows will cost $31,611. The breakdown is as follows: 76 windows of various sizes $25,223 Tax $1,828 Subtotal $27,051 Labor(76 @ $60 each) $4,560 Grand total $31,611 This project can be funded without new appropriations through the use of surplus money accumulated in the completed CIP account for the Parking Fund. Various completed projects, Nipomo/Pahn parking lot in particular, have accumulated surplus funds in excess of$200,000 for unexpected capital projects such as the window upgrade. Thus, the project can be readily completed without any fiscal impact to current approved projects. ALTERNATIVES The property owner and the Public Works Department have reached an agreement on the number of windows to be replaced to satisfy both parties. However, the Council can direct staff to replace more or less than the recommended number of windows if it so desires. ATTACHMENTS Attachment 1-1986 Mitigation Measure for the Palm Garage Attachment 2—Krause Engineering Sound Study Attachment 3—Dubbink Associates Sound Study Attachment 4--Krause Engineering Window Replacement Schedule counci Iagendareport/parkingissues/CARHowardFranklinSound C3-3 ATTACHMENT 1 REQUIRED MITIGATION MEASURES - ER 17-86 New Parking Structure Northwest corner of Morro and Palm Streets The following measures are include in the project to mitigate potential adverse environmental impacts. Please sign the original and return to my office as soon as possible. 1. Left turn lanes northbound from Morro onto Palm and eastbound from Palm into the structure should be considered to assure that cars can safely turn into the structure. 2. Construction should begin during the summer, if possible, to minimize problems with excavation and runoff, to minimize the overlapping of time during which the parking structure and City-County Library are under construction and to allow for some spaces to be available for shoppers during the month of December. 3. The BIA, City and County should encourage their employees to carpool and should consider setting up a carpool or vanpool site. 4. A parking management plan shall be established to encourage merchants and their employees and government employees to utilize the garage and to remove parking from residential areas. 5. If the structure is always open to the public, adequate lighting and regular police patrol of the site should be provided. If the structure will be closed at certain times, a security barrier such as a gate shall be installed at the entrance. 6. Building design shall assure that adjacent residents are not exposed to car exhaust and venting from the structure. 7. Adequate ventilation within the structure shall be provided to ensure a safe environment for its users. 8. some means of minimizing noise to the adjacent apartment shall be provided, such as double-glazing windows of that unit and/or constructing a noise barrier between the structure and adjacent residences in compliance with city's noise standards. 9. Existing trees within five feet of the property line shall remain. C3-4 MAY 3 0 ..,,00 ATTACMfET 2 Krause Engineering Services City of SLO - Parking Operations May 25, 2000 1260 Chorro St., Suite B San Luis Obispo, CA 93401 Attn: Keith Opalewski Subj: Traffic Noise Study Palm Street Garage Introduction The study subject is an existing multilevel parking garage in downtown San Luis Obispo. One side of the garage faces directly toward adjacent apartment buildings, with potentially significant noise impact on residents. The study objective is to assess the noise impact of traffic in the garage with respect to the City of San Luis Obispo General Plan Noise Element, and recommend n itigations if necessary. The study method includes a recent survey of noise levels made at the garage property line adjacent to the apartments. Setting The garage is located at the northwest corner of the intersection of Monro and Palm Streets as shown in Figure 1; garage arrangement with respect to the adjacent apartment buildings is shown in detail in Figure 2. The northwest comer of the garage and the portion next to the office building have solid walls, indicated by bold lines. Other sides of the garage are open or have decorative louvered sheet metal facings which are acoustically transparent to traffic noise. The main access to the garage is at a toll kiosk on Palm Street. An alley adjacent to the apartment building serves as an auxiliary access for monthly parking patrons. A small office building is at the corner of the garage property next to the alley;this building is currently being renovated. The remaining space on the north side of the garage is designated as a handicap parking area; this space is currently fenced off and is being used as a staging area for the office renovation project. Dominant noise source observed in the area is local traffic on Morro and Palm Streets; noise from other city streets and Highway 101 is also audible during lulls in local traffic. A significant stationary noise source in the area is rooftop mounted mechanical equipment(heat pumps) for the Pacific Bell switch gear building across Morro Street from the apartments; this is the dominant noise source late at night when traffic is minimal. Noise Descriptors Sound magnitude is measured using a decibel (dB) scale to describe the relative intensity of acoustical pressure waves. The subjective impression of a given sound is a function of both sound wave magnitude and frequency content, and is called loudness. Loudness is measured using a frequency weighting scale(A-weighting) which relates measurements to human hearing response. Noise is rated using a loudness scale of A-weighted sound levels expressed in dB. Annoyance due to noise is associated with how often the noise is present and how long it persists, as well as how loud it is. Variable noise levels are described by Equivalent Sound Level (L*, which is the average noise level over a given time period. Community noise is rated using the Day- Night Average Sound Level (Ldn), which uses hourly Leq values averaged over a 24-hour day, with the addition of a 10 dB penalty for the nighttime hours between 10 pm and 7 am. 6086 Gary PI. . San Luis Obispo, CA 93401 (805) 546-8169 FAX 546I8N_5 Palm St. Garage Noise Page 2 Noise Criteria The City of San Luis Obispo Noise Element includes policies to avoid or reduce the impact of community noise sources on residences. This includes maximum allowable noise levels at residences due to emissions from both traffic and stationary sources as follows. Maximum daily average noise exposure due to traffic: Outdoors 60 dB Ldn Indoors 45 dB Ldn Hourly noise exposure due to stationary sources: Maximum 70/65 dB (Day /Nigat) Average 50/45 dB Leq (Day/Night) Noise Survey A noise measurement survey was performed during the period from April 13 (a Thursday) through April 16(a Sunday) in order to assess typical noise exposure at various times of the week The survey included sessions in the evening during Farmers Market, late at night on Friday and Saturday, and midday Saturday . Data were obtained at three survey stations located along the property line as shown in Figure 1; the stations are similar except for distances from Morro Street. The survey used a precision sound level measurement system which logged sound levels at one- second intervals for continuous periods of 15 to 30 minutes duration each. Maximum and minimum sound levels(Lmax and Lmin) were determined for each period, along with average sound level (Leq) for the entire period. Records were annotated with observations of noise sources during specific events which had significantly higher levels than usual. Survey Results Results of the survey are shown in Table 1. Minimum levels ranged from 48 to 53 dB, depending on the amount of traffic on distant streets and the highway. Minimum noise levels late at night were 49 dB at Station 2 and 48 dB at station 3; these are due to the rooftop equipment sources at the Pacific Bell building, which operate continuously (Station 2 is slightly closer to the source). Maximum sound levels were from 60 to 75 dB, due to traffic on Morro Street and in the garage. Hourly average sound levels were 51-52 dB Leq late at night and 55-56 dB Leq during most daytime and evening sessions. The highest hourly average value of 58 dB Leq occurred during the Farmers Market, when the garage was essentially full. Typical sound level record segments are shown in Chart 1. Background noise levels from distant traffic are about 53 to 57 dB. Momentary peaks of 60 to 65 dB occur during traffic passbys on local streets and in the garage. Periods with maximum sound levels 65 to 68 dB resulted from car alarms in the garage; in one case, the alarm sounded continuously at 68 dB for about one minute. Other records are similar, with highest noise level events caused by truck or bus passbys on Monro Street, and by alarms or horns of cars both parked in the garage and on city streets. C3-6 Palm St. Garage Noise Page 3 Other specific sources of intrusive noise events were vehicles with poor quality mufflers (i.e. jalopies, low riders, and diesel pickup trucks), loud car stereos, racing by particularly aggressive drivers racing, and the alarm horn used to warn oversized vehicles at the garage entrance kiosk. Much of the traffic noise which might seem at first to come from the garage is in fact Palm Street traffic noise passing through the open structure of the garage. This is particularly significant for busses, trucks, and trolleys accelerating away from stop signs at the intersections. Average Traffic Noise Exposure Equivalent average daily noise exposure at the rear alley property line can be predicted with confidence using the survey data as shown in Table 2, using hou.ly Leq values assumed for a 24- hour day starting and ending at noon. Daytime noise levels are 55 to 57 dB Leq, with peak morning and afternoon hours of 58 dB Leq. Early morning and late evening noise levels are 53 to 55 dB Leq. Nighttime noise level is 51 dB due to stationary sources. Hourly Ldn values are calculated by adding 10 dB to nighttime hours shown in bold type; overall daily average noise exposure calculated by logarithmic addition of hourly Ldn values is 59 dB Ldn. The daily average is less than the allowable maximum of 60 dB Ldn; mitigation is not required Stationary Source Noise Exposure Continuous noise levels of 48 to 49 dB due to Pacific Bell equipment were measured at the survey stations near the alleyway. Noise levels of 53 to 55 dB due to this equipment also were measured at locations along the east lawn area of the apartment building facing Morro Street. Even higher noise levels are predicted at upper floor windows and balconies of the apartment building. The average noise level due to this source is greater than the allowable limit of 45 dB at night; mitigation (by Pacific Bell) to allowable limits is recommended. This also would reduce overall daily Ldn by lowering the background level during late night hours when traffic is not significant and the 10 dB penalty is applied. Discussion Although no mitigation is required to comply with the Noise Element standards for daily average traffic noise exposure, the isolated noise events as described above in the discussion are a likely a source of occasional noise intrusion and annoyance to the apartment residents. Although individual drivers' actions are largely not under control in the garage, some benefit would likely be derived by advising garage patrons of the presence of residences nearby, and discouraging excessive horn use, loud music, and driving fast. This could be done by posting signs at the kiosk entrance and at selected locations in the traffic flow path, or by including a note on the preprinted garage parking tickets. The garage security staff rovers also could assist by advising noisy patrons about the neighbors and requesting cooperation. IA4-d14Wt. Nick Krause, P.E. Krause Engineering Services C3-'7 FIGURE 1 VICINITY MAP L_I Ick � F o J PRLl11 _ _ r= �- -� M OW.ERHY MONTEREY M M ,I i I i7 W7 ITF--Ti FIGURE 2 IJ LOCAL AREA DETAIL � L- MILLrL U N � J ~ w am Za Lu 2 2 a a a HANDICAP PARK GARAGE 4 PALM C3-S TABLE 1 TABLE 2 NOISE SURVEY DATA DAY-NIGHT AVERAGE DATE SURVEY START DUR Sound Level, dB Hourly STN. TIME (min) Lmax Lmin Leq Leq HR Leq Ldn 4/13 1 18:00 30 69 53 58.9 58 12 56 56 18:30 30 66 53 56.8 13 56 56 " 19:00 30 75 51 57.5 56 14 56 56 19:30 30 73 50 55.4 15 56 56 " 20.00 30 69 49 56.2 16 57 57 17 58 58 4/14 2 20:00 15 58 54 54.7 55 18 57 57 20:15 15 61 52 54.2 19 56 56 " 2 0:3 0 15 73 52 55.6 20 55 55 20:45 15 65 51 53.9 21 53 53 2 2 5 2 6 2 4/14 2 23:45 1 5 59 50 51 .9 2 3 5 2 6 2 4/15 00:00 30 68 49 52.6 52 0 5 2 6 2 " 00:30 30 63 49 51 .9 1 51 61 " 01 :00 25 64 49 51.4 2 51 61 3 5 1 6 1 4/15 2 13:30 30 74 51 57.1 56 4 51 61 " 14:00 30 68 52 55.2 S 5 2 6 2 14:30 30 69 52 56.0 6 5 3 6 3 7 55 55 4/16 3 00:15 15 59 48 50.2 8 57 57 " 00:30 30 62 48 51 .1 51 9 58 58 01 :00 30 . 62 48 50.1 10 57 57 01 :30 30 70 48 51.2 51 11 56 56 " 0 2:0 0 30 60 48 49.9 " Ldn 5 9 C3-9 CHART 1 EVENING TRAFFIC NOISE PALM ST GARAGE, SLO APR. 14, 2000 6:00 pm • Station 1 Leq = 58 dB 5 65- Cr 5 tr S S [cdIB60- 5 5 `L 55- 4 - 50- 1 0 1 2 3 4 5 6 7 8 9 10 MINUTES 6:15 pm • Station 1 Le = 58 dB 70- A S dB 60- 55' 0 1 2 3 4 5 6 7 8 9 10 MINUTES 8:15 pm • Station 1 Leg = 56 dB 70- 65- S S S dB 60- G (r !r 55- 50-1 i 0 1 2 3 4 5 6 7 8 9 10 (�ry- / MINUTES �: rlAraafQ ,.gie. S �-t rw j VY.Ii:[ A : C3-10 ATTACHMENT 3 David Dubbink Associates Interactive Sound Information system 864 Osos Street, Suite D, San Luis Obispo, California 93401 USA Tel: (805) 541-5325 Fax: (805)54145326 email: dubbink@noisemanagement.org July 6, 2000 Mr. Howard Franklin 891 Mill Street San Luis Obispo, CA 93401 Dear Mr. Franklin: This is a response to your request to review the city's May 1, 2000 noise study and recommendations. As the text of the Krause Engineering report states,the city has multiple noise standards that need to be met by all approved projects. The Current Situation The city sets standards for single event, hourly and daily levels. The standards for single event and hourly exposure are: Maximum(Lmax) 70/65 Day/Night Average(LEQ) 50/45 Day/Night The Krause Engineering study indicated that noise from the parking structure is in excess of the city's standards for maximum and hourly exposure. The study measured noise at three locations along the property line adjacent to the garage. The maximum sound levels recorded were at 68 dB for a one minute period caused by an activated car alarm. Other peak events related to a warning horn for oversized vehicles and tine screeches from racing cars. The maximum hourly level of 58 LEQ was recorded at the time of Farmer's Market. Krause Engineering estimated the daily noise level dose to be 59 DNL. This is just under the permitted 60 DNL limit. We conducted our own study of the situation using a hand held sound level meter(B&K Type 2230). Our readings of background noise were in line with the Krause study. They report typical background noise levels(mostly area traffic) are in the range of 53 to 57 dB. We recorded background levels at 56.6 in the early afternoon of July 1. However, we set up a"worst case" scenario. We parked a truck in a parking stall on the second level of the structure in the row facing your building. We set off the electronic alarm using a remote.The alarm produced the familiar repetoir of warbles,whoops and honks. We also made our measurements from elevated positions, at the top of an outside stair and from an open bedroom window at the third story. The alarm produced a maximum level of 77 dB and an average,while sounding, of 74 dB. With the window closed the maximum sound was 58 dB with a side window open and 55 dB with all windows closed. This 19-22 dB reduction is consistent with conventional construction. C3-11 We were also interested in the audibility ofthe alarm within courtyard area on the apartment building. This faces "southward"and is not directly facing the parking structure. At the upper level balcony there was a minimal 2 dB change from 58 dBs of background noise to 60 dBs with the alarm activated. However,the sensory experience was different than the dB readings would suggest. The alarm sound is designed to be attention getting. We could hear the alarm quite clearly with the sound echoing back from the side of the apartment building facing the structure. At this location, most of the background sound comes from freeway noise. This would be reduced at evening and nighttime periods so the differential effect of sounds from auto alarms, warning horns, and screeching tires would be magnified. The Krause study concluded that noises from the garage, "are a likely source of occasional noise intrusion and annoyance to the apartment residents." We concur with this and note that the situation is even more problematic with our`worst case"of an activated car alarm in the first rank of cars. Suggested Mitigations In the section of the Krause study on mitigations it was suggested that drivers be asked to avoid using horns within the garage and to drive at moderate speeds. Perhaps this might have some effect but it is unlikely that drivers would disable car alarms or that all drivers would comply with the requests. The original project approvals included sound insulation treatment for the apartment structure. This is justified by the current situation. The parking structure produces noise in excess of that permitted by the city's standards. Dual paned, acoustic windows can reduce noise exposure by 10 dB and can bring noise exposure within the living and sleeping areas fronting the garage to acceptable levels. In order to produce appropriate reductions in room noise levels it is necessary to treat all openings. This requires treatment of fronting and side facing windows as well as structural ventilation openings at the roof line and in the foundation area. If rooms are completely closed, it is also necessary to provide forced ventilation—and the ventilators must be designed to suppress exterior noise. We recommend that a contractor with experience in acoustical insulation make specific recommendations as to how to most economically bring the situation into conformance with city noise standar S' cerel , David Dubbink, PhD., AICP C3-12 ' TACHKM 4 Krause Engineering Services FAX MEMO - 3 PAGES TO:(805) 781-7267 To: SLO Parking Authority August 25, 2000 1260 Chorro St. Suite B San Luis Obispo, CA 93401 Attn: Keith Opalewski Re: Traffic Noise Study Palm Street Garage, SLO I have reviewed the recent car alarm noise study (Dubbink, 7/6/00) and recommendations for treatment to reduce nuisance noise at the adjacent apartment building. The following is my response. My prior study (Krause, 60/00) specifically assessed the garage noise with respect to the day-night average noise level (DNL) limit, which is applied in the Noise Element to "transportation" sources such as public roadways On this basis, the surveyed noise levels at the apartment property.line do not exceed limits and no mitigation is required. The Dubbink study made some additional average noise level measurements which are consistent with the Krause survey. The Dubbink study also investigated the peak or maximum noise levels due to car alarms located in portion of the garage directly adjacent to the apartments. Dubbink demonstrated that the maximum sound levels due to car alarms exceed the Noise Ordinance allowable limits and the Noise Element allowable limits for "stationary" sources such as mechanical equipment or commercial facilities. These results are consistent with the maximum noise levels observed in the Krause survey. I have also reviewed the window replacement schedule proposed by the apartment owner and the review by Mr. Trujillo- I agree that the borderline necessity of mitigation in terms of noise descriptors, along with vague wording of the initial mitigation measures recommended, merits at least some action by the city. 58 VIA LA CUMBRE GREENBRAE, CA 94904 (415) 461-5403 C3-13 Palm Street Garage Page 2 The proposed replacement of windows is the most effective way to reduce indoor noise in an existing residential building. Normally this is done only for windows facing toward the noise source. The proposed replacement window schedule (see attached sketch) shows a total of 65 such windows, including those on the south and west faces of the building and on the south face of the courtyard. All these will require replacement. The sketch also includes 12 windows on the north and east faces of the building. These windows do not face toward the garage, and are primarily exposed to traffic noise on Mill and Morro Streets. Replacement of these windows as part of the work is not recommended. The sketch also includes I 1 windows on the north face of the courtyard. Although these do not face the garage directly, they are exposed to reflections of garage noise from the other courtyard walls. Replacement of these windows questionably necessary on purely technical grounds, but is a reasonable good faith concession to the apartment owner. Regards, I-IW/f�f� Nick Krause, P.E. Krause Engineering Services C3-14 r' �7 wYsh� TO I-0 I C3-15