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HomeMy WebLinkAboutGARDENS ON SPRING CREEK - MAJOR AMENDMENT - MJA150006 - SUBMITTAL DOCUMENTS - ROUND 1 - SUPPORTING DOCUMENTATIONAugust 26, 2015 Mr. Craig Russell, Principal Russell + Mills Studios 141 S College Street, Suite 104 Fort Collins, Colorado 80524 RE: Gardens on Spring Creek – Noise Modeling Narrative (DLAA #9678A) Dear Craig, Per your request, we have updated our acoustical model based on the most recent stage design and expanded modeling area for the Gardens on Spring Creek in Fort Collins, Colorado. Included in this report are results from the updated model and a narrative explaining the analysis and modeling methodology. Please note that our comments and recommendations are based entirely on meeting acoustical objectives. Compliance with building codes should be reviewed by qualified personnel prior to implementing any recommendations. Modeling We have modeled several scenarios to predict the noise impact of the proposed Gardens on Spring Creek Amphitheatre based on architectural and landscape drawings, locations of adjacent buildings and neighborhoods, the surrounding topography, conversations with the architect, and meetings with the City of Fort Collins and representatives from the Gardens. The models were made in CadnaA, a computer aided environmental noise assessment and predictions software which allows for 3D noise mapping based on the layout of the environment and designated source and receiver locations. The model was constructed by overlaying the plans for the proposed Gardens renovations over a map of the existing site with building locations and terrain contours. Three dimensional models of sound reflecting features such as buildings, sound barriers, and the stage were then placed according to their location on the site plan. The building models account for their roles in regard to both blocking and reflecting sound. Receiver locations indicating resulting sound levels were placed in the neighborhoods of concern to the west, northwest, and south of the Gardens. Another receiver location was placed in the center of the lawn at the assumed mixing console location in order to calibrate source levels. The sound source used in the model consisted of two subwoofers on the stage and two line array stacks placed on the stage and directed toward the audience area. This sound source is similar to Mr. Craig Russell August 26, 2015 Page 2 what we would expect for concerts and events. Source levels were calibrated so that the level at the assumed mixing console location was 90 dBA. We recommend that a 90 dBA limit at the assumed mixing location will need to be established in order to prevent excessive sound levels at the nearest properties. In addition to the loudspeakers, an audience area was added to the lawn in front of the stage to simulate the noise impact that a 1,500 member audience may have on nearby sound levels. The predicted sound spectrum of the audience was based on prior concert crowd noise measurements, and the overall level was calibrated based on the expected sound level of concerts at the Gardens. Design Criteria Section 20-23 Maximum permissible noise levels of the Fort Collins Municipal Code and Charter establishes maximum noise levels in Low Density Residential zones (R-L) to be 55 dBA from 7:00 am to 8:00 pm and 50 dBA from 8:00 pm to 7:00 am. It is our understanding that the Gardens on Spring Creek have agreed to stop performances at 8:00 pm in order to remain in the 55 dBA limit window. Our recommendations will be based on meeting the 55 dBA noise limits. The maximum noise levels in Employment zones (E) is 70 dBA from 7:00 am to 8:00 pm. The surrounding area of the Gardens on Spring Creek consist of both Low Density Residential, and Employment zones. Zone boundaries as well as property lines are shown and labeled in the noise mapping graphic attached. Recommendations Stage Design Our recommendations shown in Figure 1 are based on the latest design of the Gardens on Spring Creek stage. The design features a segmented wall along the north and west edges of the stage, and a curved floating roof structure. The northwestern and western segments of the wall extend up to the bottom of the roof structure, which will help prevent a direct path for sound to travel form the stage to the residential zone to the west. The curved western segment of the wall extends south beyond both the stage and the footprint of the roof. We recommend this portion of the wall extend up to at least 12 feet above stage level and 17 feet south of the west corner of the stage. Mr. Craig Russell August 26, 2015 Page 3 While the stage walls are beneficial for mitigating the sound directed towards the adjacent neighborhoods, the curved walls will provide unwanted sound focusing and reflections back to the stage and audience area. To address this, we recommended finishing the inner side of the stage walls with a sound absorbing material such as Pyrok Acoustement 40. Product literature is attached. Another option would be to use a splayed, tiered, or rough finish with varying depths for the stage walls that would diffuse incoming sound. Smooth, sound reflecting finishes should be avoided. Sound Barriers In addition to the stage walls, sound barriers will be needed along the western edge of the lawn. The barriers should be at least 23 feet tall; or a minimum of 17’ above the stage level on the northern end of the barrier, and a minimum of 19.5’ above stage level on the southern end. Figure 1 shows recommendations for the barriers in regards to minimum height and approximate location relative to the stage. If the barriers are curved to match the perimeter of the lawn, the barriers will focus sound, and similar treatment to the stage walls will be needed; either a sound absorbing or sound diffusing finish should be used. Breaking up the sound barriers into smaller or straight segments will also help prevent unwanted reflections. If this is done, the barrier segments should be staggered to fully block the line of sight from the stage with no gaps and at least 7 feet of overlap between them. Loudspeaker Placement and Restrictions In order to keep the sound barriers down to a reasonable size, height limits for loudspeakers brought in for shows need to be established. All loudspeakers used for events should be stage mounted and be no higher than 9 feet above the stage. The sound pressure level in the center of the audience area should not exceed 90 dBA. Predicted Results Noise contours showing the predicted conditions with our recommendations incorporated is displayed in Figure 2. The map shows the predicted sound level at receiver points in various locations throughout the surrounding area. The predicted sound level at the worst case condition in the residential zone is below the 55 dBA limit. Sound levels in the adjacent properties zoned for employment are not expected to exceed 68 dBA, which is below the 70 dBA limit. As shown by the noise contours in Figure 2, the building to the south of the Gardens will not provide significant sound reflections back to the lawn or the adjacent neighborhoods. The reflections are minimized due to the directionality of the loudspeakers on the stage being aimed downward toward the audience and reducing the sound that is directed to the buildings. The sound level in the audience area and adjacent neighborhoods from sound reflected off the building will be well below the level of direct sound from the stage and main loudspeakers. Mr. Craig Russell August 26, 2015 Page 4 The sound generated by the audience will be mostly directed toward the stage. The level of any noise from the audience reflected off the buildings is expected to be below the direct sound level from the main loudspeakers. The reflected audience noise is not predicted impact the overall sound level in the adjacent neighborhoods. Please let us know if you have any questions. Sincerely, Ian Patrick Staff Consultant Enclosed: Figures 1 and 2 Product Literature 17' Extend wall 17' south of west stage corner. Minimum 12' above stage level. Stage Wall and Sound Barrier Layout Figure 1 August 26, 2015 not to scale Interior barrier finish shall be sound absorbing or diffusive. Curved stage walls shall be sound absorbing or diffusive. Interior Interior barrier barrier finish finish s shall be sound absorbing or diffusive. Extend to a minimum 17' above stage level. Extend to a minimum 19.5' above stage level. Extend to a minimum 19' above stage level. 90.0 51.4 50.2 54.3 47.4 48.8 62.3 61.9 50.1 67.1 67.9 59.0 54.7 63.4 90.0 51.4 50.2 54.3 47.4 48.8 62.3 61.9 50.1 67.1 67.9 59.0 54.7 63.4 90.0 51.4 50.2 54.3 47.4 48.8 62.3 61.9 50.1 67.1 67.9 59.0 54.7 63.4 90.0 51.4 50.2 54.3 47.4 48.8 62.3 61.9 50.1 67.1 67.9 59.0 54.7 63.4 150 150 200 200 Pyrok Acoustement 40 Decorative/Acoustical Surfacing Material Product Data 1. Description Pyrok Acoustement 40 is a nominal 41 PCF (air-dried density) Portland cement/exfoliated vermiculite spray-applied formulation 100% free from asbestos and mineral fibers, polystyrene, and cellulose. Pyrok Acoustement 40 is highly abuse resistant (impact, abrasion, moisture, hostile industrial environments), has excellent adhesion to a variety of substrates, allows substrates to breath and be cleaned by a variety of methods. 2. Uses Pyrok Acoustement 40 can be used as a decorative surfacing material or as a combination of these qualities even in conjunction as a fireproofing material. This material is recommended for exterior exposures where resistance to environmental pollution, rain, corrosion, and spalling is required. It may be used in interior exposures where superior abuse resistance is required. Typically Pyrok Acoustement 40 is specified for transportation facilities, correctional projects, lobbies, atriums, tunnels, natatoriums, gymnasiums, manufacturing facilities, contact wall areas, and any other area requiring high abuse resistance and sound absorption qualities. It can also be used on interior surfaces of walkways, hallways, and rooms where a purely decorative finish is desired. Pyrok Acoustement 40 may also be used on ceilings as a combination acoustical finish and fireproofing material. Custom integral coloration is available within the limits of iron oxide pigmentation. 3. Packaging 35lb. Kraft paper/polyethylene lined bags 55 bags shrink wrapped pallet (minimum) 1100 bags per truckload 4. Yield 17 Bd. ft./bag (ideal) 5. Applications Pyrok, Inc. recommends application of Pyrok Acoustement 40 be performed only by approved Pyrok applicators. An approved applicator list is available from Pyrok, Inc. 6. Application Procedures Summary Pyrok Acoustement 40 may be applied directly to clean, bare steel, clean galvanized steel or a wide variety of unpainted concrete, cement board and other clean, sound substrates. Some substrates will require metal lath. Contact Pyrok, Inc. for verification of compatibility with substrate, suitability of primer and potential requirement of expanded metal lath. Mix in mechanical type mixer with paddle or ribbon type blades. Use 4-5 gallons of clean, potable water per each 35-pound bag of Pyrok Acoustement 40. Mix 1 to 3 minutes. Spray-apply using equipment recommended by Pyrok, Inc. Air supply at the spray nozzle shall be a minimum of 40 pounds per square inch. Wet density at the nozzle shall be 70-85 pounds per cubic foot. Application Brush or roll-apply a liberal coat of Weldcrete to substrate immediately prior to application of Acoustement 40. Apply a splatter coat covering 60% to 80% of the substrate surface. Allow splatter coat to cure overnight. Successive coats of Pyrok Acoustement 40 shall not exceed 1/4 inch thick per application. Thicknesses that exceed 2 1/8 inches may require metal lath. Contact Pyrok, Inc. to determine if metal lath is required. Topcoating/Curing Pyrok Acoustement 40 may be supplied in several integral colors or may be topcoated for more pleasing aesthetic finish or for curing. Consult Pyrok, Inc. for further information regarding suitable topcoating and curing compounds. Patching or Repair Contact Pyrok, Inc. or your construction representative for patching or repair procedures. Cleaning Wet Pyrok Acoustement 40 may be removed by brushing or with water. Dry Pyrok Acoustement 40 may require scraping or chipping to remove. Pyrok Acoustement 40 may be steam cleaned or pressure washed after full cure (minimum 28 days). Storage and Shelf Life Store Pyrok Acoustement 40 off the ground in unopened, original packages and keep dry. Pyrok Acoustement 40, kept dry, has a five (5) year shelf life. Warranty Manufacturer warrants the material to be supplied, agreeing to replace that which has cracked, flaked, dusted excessively, peeled or fallen from substrate, or otherwise deteriorated to a condition where it would not perform effectively as intended for fire protection and sound absorbent purposes; due to defective materials and not due to abuse, or improper maintenance, unforeseeable ambient exposures or other causes beyond anticipate conditions by manufacturer. The warranty period will be 10 years from date of installation. Manufacturer’s liability under any expressed or implied warranty is limited solely to replacement of Pyrok products proved defective and does not include labor or other consequential damages. The suitability of the product for any intended use shall be solely up to the user. The express warranties set forth herein are in lieu of all other warranties, express or implied, including without limitation, any warranties or merchantability or fitness for a particular purpose. In no event shall manufacturer be liable for any direct, indirect, incidental, or consequential damages resulting from any defect in the material even if manufacturer has been advised of the possibility of such damages. Physical Performance Properties Property Test Method Value Asbestos Content EPA 400/4M-82-020 No Asbestos No Mineral Fiber Bond Strength ASTM E 736 5000 PSF Compressive Strength ASTM E 761 300 PSI Density ASTM E 605 41 PCF (Avg) Sound Absorption ASTM C 423 0.60 NRC @1” Surface Burning ASTM E 84 0 Flame Spread 0 Smoke Developed Toxicity University of Pittsburgh LC(50)>300 Grams Toxicity Test Combustibility ASTM E 136 Non-Combustible Sound absorption coefficient on solid backing with no air gap ASTM C 423 Frequency (HZ) 125 250 500 1000 2000 4000 NRC Absorption Coefficient @ 3/8” 0.17 0.20 0.29 0.34 0.56 1.00 0.35 Absorption Coefficient @ 1/2” 0.01 0.20 0.43 0.68 0.75 0.80 0.50 Absorption Coefficient @ 1” 0.18 0.35 0.64 0.73 0.73 0.77 0.60 Absorption Coefficient @ 1 1/2” 0.36 0.51 0.64 0.74 0.84 0.91 0.70 Absorption Coefficient @ 1 5/8” 0.24 0.59 0.74 0.81 0.91 0.97 0.75 Acoustement 40 Data | Distributed by Pyrok, Inc. | info@pyrok.com | www.pyrok.com 250 250 300 300 350 350 400 400 450 450 500 500 550 550 600 600 650 650 50 50 100 100 150 150 200 200 250 250 300 300 350 350 400 400 450 450 500 500 550 550 600 600 650 650 700 700 750 750 800 800 90.0 51.4 50.2 54.3 47.4 48.8 62.3 61.9 50.1 67.1 67.9 59.0 54.7 63.4 > -99.0 dB > 35.0 dB > 40.0 dB > 45.0 dB > 50.0 dB > 55.0 dB > 60.0 dB > 65.0 dB > 70.0 dB > 75.0 dB > 80.0 dB > 85.0 dB Stage walls Zoning boundary Property Line Employment Zoning (70 dBA) Residential Zoning (55 dBA) Sound Barrier West wall 12' above stage minimum Predicted Sound Level Map Figure 2 August 26, 2015 not to scale Centre Ave. Min 19.5' above stage level. Min 17' above stage level.