2017-046 - Approving Addendum Nos. 1 and 2

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OCTA I Santa Ana/Garden Grove Fixed Guideway Project FNNoise and Vibration Technical Addendum Table M: Summary of Traction Power Substation Noise Impacts TPSS Distance to closest land use (feet) Land Use Cat. Existing Noise Level Ldn or Lday (dBA) TPSS Noise Level FTA Impact Criteria Ldn or Lday (dBA) Impact 1 75 2 50 42 dBA Ldn 54 No Impact 2 100 2 57 40 dBA Ldn 57 No Impact 3 200 3 61 38 dBA Lday 64 No Impact 4 1 100 1 3 1 54 1 44 dBA Lday 60 No Impact Source: URS (February 2012) and HDR (June 2016). Notes: TPSS#1 and TPSS#2 noise levels are based on an orientation where the HVAC units are located on the opposite side of and directed away from the closest receptors. Land Use Category 2: Residences and buildings where people normally sleep. Land Use Category 3: Institutional land uses with primarily daytime and evening use. FTA Impact Criteria: The noise level below which no impact would occur. Based on the land use category and the existing noise level. No Impact: A proposed project is considered to have no noise impact since, on average, the introduction of the project will result in an insignificant increase in the number of people highly annoyed by the new noise. Moderate Impact: The change in the cumulative noise level is noticeable to most people, but may not be sufficient to cause strong, adverse reactions from the community. Severe Impact: A significant percentage of people would be highly annoyed by the new noise. The City of Santa Ana's Municipal Code noise limit for nighttime activities near sensitive land uses is 50 dBA for events that occur for more than 30 minutes in a one hour period. This limit is reduced by 5 dBA, to 45 dBA, for noise consisting entirely of impact noise, simple tone noise, speech, music, or any combination thereof. TPSS units 1 and 2 are located in residential areas. As the Ldn noise levels listed in Table M are 6 dB higher than the hourly Leq noise levels, the TPSS nighttime hourly noise levels would range from 34 to 40 dBA Leq. Therefore, the sensitive land uses located within the vicinity of the proposed TPSS units would not be exposed to noise levels exceeding 45 dBA. However, it is recommended that the following measures be implemented to ensure that the impact is below a level of significance: - Orient the TPSS unit so that the HVAC units, the primary source of noise, are pointing away from the nearest residence. - At the residential locations, the TPSS units will be designed so as not to exceed a maximum noise level of 45 dBA at a distance of 50 feet from the unit or at the setback line of the nearest building, whichever is closer. 14