AgdaPkt 2010-01-25 clsd and regular

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6.2A Page 29 Impact NOI-2c: Noise levels caused by nighttime tunnel construction would generate noise levels beyond the time limits and in excess of the noise limit increases established by the City of Newark's noise policy. Tunnel construction activities may extend beyond the workday hours allowed by the City of Newark (7 a.m. to 6 p.m. on weekdays only). During these hours, construction activities would not be subject to the City's noise limits. However, construction activities occurring beyond established workday hours would be subject to the City's noise policy that limits noise increases to 6 dBA above the ambient noise level at the property line. Nighttime activities could include operation of two cranes, tunnel ventilation fan, front-end loader, and stationary equipment. Ventilation fans are required at all times that workers are underground, which would be up to 24- hours a day, cranes would be operated at night to raise and lower workers as necessary, and pumps would be operated as often as necessary (up to 24-hours per day) to maintain dry working conditions underground. This equipment could generate noise levels of 37 to 54 dBA (Leq) at the closest residential property line with direct line-of-sight approximately 1,650 feet away for a combined noise level of 56 dBA (Leq). The estimated combined noise level of 56 dBA (Leq) would increase the ambient noise level by more than 6 dBA at the property line, and thereby generate noise levels in excess of noise increase limits established by Newark's noise policy, resulting in a significant impact. . Mitigation Measure NOI-2: Noise reduction techniques and time limit restrictions. Impact NOI-2e: Noise levels from equipment used for pipeline and tunnel construction could exceed the City of Newark General Plan's Noise Element. The City of Newark's Noise Element contains weekday limits on noise for construction equipment by type, as measured 50 feet from the piece of equipment. Unmitigated weekday noise levels at 50 feet would exceed Newark's noise limits for construction equipment, resulting in a significant impact. . Mitigation Measure NOI-2: Noise reduction techniques and time limit restrictions Impact NOI4: Operational noise could exceed local noise ordinances. The Project proposal includes new backup power sources at the Hayward Fault Valve Lot East and Hayward Fault Valve Lot West consisting of high-pressure hydraulic power. At these two valve lots, a battery backup power would be included to operate the hydraulic compressor in the event of power failure. The battery must be kept at an optimum temperature to maintain its shelf life; therefore, air-conditioning equipment would be required. Residential receptors are located within 170 feet of the Hayward Fault Valve Lot East and within 10 to 40 feet of the Hayward Fault Valve Lot West. These air conditioners would be a new permanent noise source for adjacent residents, but noise increases would be similar to those associated with residential air conditioning systems, which would typically be le~s~t~~~,sigl1jf:icant:Jlo~~Y~~~~~:t1,(;~"l1()i~~.., .. .... ::leVelsthatwoiild be jirodiiced by the' installation of-the discussed equipment' are 'notknown'at. ,. this time, this would be a potentially significant impact. Propane-fueled permanent emergency generators would be installed at the Newark and Ravenswood Valve Lots, while a portable generator connection would be installed at the Redwood City Valve Lot. Residential uses with direct line of sight are located approximately 2,000 feet from the Newark Valve Lot, 900 feet from the proposed Ravenswood tunnel shaft location, and 100 feet from the Redwood City Valve Lot. Emergency generators can generate noise levels of81 dBA at 50 feet, but these noise levels can vary with the size of the generator. At these distances, the proposed generators could produce noise levels of approximately 50 to 75 19