4.13 Noise
character from the ambient surf noise, and because the overall average noise level would be anticipated to
increase 3-6 dBA.
As the work would move away from any individual receptor, the noise level would decrease, and at a
distance of 200 feet, a decrease of 10-12 dBA would be anticipated. At that distance, maximum
construction noise levels would be 65 dBA or less, and average noise levels on the order of 55 dBA Leq.
At nighttime, when work would occur within 200 feet ofa residence, the change in noise environment could
be anticipated to disturb the sleep of some residents. While closing the windows would reduce the noise
level, the change in the volume and character of the noise, if one normally sleeps with windows open, may
disturb sleep as much as an increase in noise would. The nighttime construction noise would be an adverse
impact. However, the impact would be less than significant because residents would be notified at least
one week in advance of the work near their homes, and the work would last no longer than three
consecutive days within a distance where the noise might cause a sleep disturbance.
The approximate minimum distance from the dredge to beachfront receivers is 4,500 feet. This occurs at
the Cardiff and Del Mar receiver sites. Noise attenuation from a point source, at that distance, due to the
spreading of energy and atmospheric effects would be approximately 45 dBA. With a 90 dBA source
noise at the dredge, the resulting noise level at a beach front residence would be approximately 45 dBA.
With the normal prevailing onshore wind, noise levels may seem slightly greater. However, a noise level
of 45 dBA would be much less than the normal ambient noise level from wave activity on the beach, and
noise from the dredge would not be expected to be audible.
Booster pumps are anticipated be required for replenishment at the Oceanside, North Carlsbad and Torrey
Pines receiver sites. The pump for Torrey Pines would likely be located at or near the Del Mar receiver
site. If pump noise is 70 dBA Leq, and the pump can be located at least 250 feet from a sensitive receptor,
then the noise at the receptor would be 56 dBA Leq. This noise would be at least 5 dBA below the ambient
noise levels of 61-69 dBA, and would not be a significant impact. If a suitable location cannot be found
at a distance of 250 feet or greater, there is a choice of noise abatement measures to maintain less than
significant noise impacts: (1) A sand berm can be constructed around the pump to reduce noise; (2) it may
be possible to use an electric motor to drive the pump, rather than a diesel engine.
Page 4.13-4
Regional Beach Sand Project EIR/EA
99-69\sect-04.13.wpd 7/19/00
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