SU0014674 - Laserfiche WebLink

Home Browse Search

MOUNTAIN HOUSE NEIGHBORHOOD' 'PROJECT INITIAL STUDY an exterior to interior noise level reduction of 20 dB, therefore achieving an interior noise level of 45 dB Ldn with the windows in the closed position." Using the traffic projections prepared by the applicant, the backyard sound levels of the homes facing Central Parkway, DeAnza Boulevard, Mascot Boulevard, and Mountain House Boulevard were calculated. Without walls the following Ldn noise levels would be expected along each of these streets: Central Parkway- 71 Ldn, DeAnza Boulevard- 71 Ldn, Mascot Boulevard-69 Ldp, and Mountain House Boulevard-64 Ld,,. Without mitigation, these noise levels would exceed the goal for noise levels to not exceed 60 dB. However, for Central Parkway noise walls would not be needed because residential backyards would be within the 60 Ld(,noise level standard. The calculations indicate that 7-foot high walls along DeAnza Boulevard would reduce the outdoor noise level to 64 Ldn, and that 10-foot high walls would reduce the outdoor noise level to 60 Ldn- Along Mascot Boulevard, a 7-foot high wall would reduce the outdoor noise level to 62 Ldn and an 8-foot high wall would reduce the outdoor noise level to 60 Ldp. Along Mountain House Boulevard, a 6-foot high wall would reduce the outdoor noise level to 57 dB. In other words, soundwalls in excess of the 7-foot high maximum wall height stated in the CSD Design Manual would be required to reduce the outdoor noise level to 60 dB on Mascot Boulevard and DeAnza Boulevard. Seven-foot high walls would reduce the outdoor noise level to less than 65 dB. Interior noise levels would not exceed an Ldn of 45 dB with standard thermal insulating glass, even in 2- story homes, when the windows are closed. The units must be mechanically ventilated to allow the residents to keep the windows closed at their option. The following mitigation measures would reduce noise impacts to less than significant: Mitigation Measure NOISE-I:Soundwalls shall be included at the locations shown in Figure S to reduce the outdoor noise level to an Ld„of 60 dB unless the planning authorities deem that 1 the maximum wall height is to be 7 feet If this is the case, the residents shall be notified that the outdoor sound level has not been mitigated to the design goal of an Ld„of 60 dB. Alternatively, an exterior noise level standard of an Ldn of 65 dB(as permitted in the Master Plan)would allow the recommended noise wall along DeAnza Boulevard to be reduced to 7 feet in height and the wall along Mascot Boulevard to be 7 feet or less. The final wall heights and locations shall be determined prior to the issuance of building permits and after the grading and house location plans have been developed As an alternative to constructing taller walls, the homes could be set back farther from DeAnza Boulevard and Mascot Boulevard. Increasing the setback would allow a lower height noise wall to achieve the desired exterior noise environment However, such setbacks could reduce overall project density if lot sizes were not reduced, and thus impact the project's goals for affordable housing, non-auto related transportation and associated benefits regarding air quality and noise Mitigation Measure NOISE-2: Mechanical ventilation in homes shall be supplied for the two rows of lots on the east side of Central Parkway, two rows west of De.4nza Boulevard and jnorth Mascot Boulevard and to the first row of homes south of Mountain House Boulevard b) Exposure of persons to or generation of excessive ground borne vibration or ground borne noise levels? There are no anticipated sources that would generate excessive ground borne vibration or ground borne noise levels. C lJOBMCUNMAL SRJDY*TNAL1NrnAL=Y-PARn.D0C(7120=) 82 V.H. NOISE