700 Timberpine Avenue - City of Sunnyvale - State of California

Initial Study Checklist
Project Name: 700 Timberpine Avenue
File #2010-7672
Page 11 of 31
The report dated April 11, 201 1 discusses existing noise conditions at the site as well as applicable SMC
noise standards and thresholds.
The study measured noise levels at four locations surrounding the property. Existing noise levels were
measured at levels between DNL 60 dBa and DNL 64 dBa. To account for future traffic volumes of 1-2%,
IdB was added to the measured DNL. A future DNL of up to 65 dB is expected for the exterior noise
level. This level is considered conditionally acceptable by the City Noise Sub-Element. In order to meet
the City's goal of 60 dB, a six foot tall noise barrier is necessary for the rear yards of the proposed homes
on Lily Avenue and the house on the northeast corner of the project site on Dahlia at Toyon Avenue. This
will reduce this impact to less than significant.
An interior noise level above 45 dB is also expected to occur in the living spaces. The noise report
recommends typical dual-pane windows (STC 26-28 minimum) and standard frame construction. The
report also recommends mechanical ventilation of the units to provide for a habitable interior environment
when the windows are closed to shield noise. This will reduce this impact to less than significant.
To achieve this reduction the following mitigation measures are needed required:
WHAT: 1) A six foot tall noise barrier shall be constructed at the rear yards of the homes on Lily
Avenue and the house on the northeast corner of the project site on Dahlia at Toyon
Avenues. This barrier, as described the Salter 2011 report, must be solid from top to
bottom, have no surface gaps or cracks, and must be a minimum of three pounds per
square foot. The wall may be masonry, CMU block, or enhanced wood.
2) To achieve compliance with the 45 dB interior noise level standard, Sound
Transmission Class minimum rated 26-28 windows shall be installed near all living
spaces.
3) All units shall have a ventilation or air-conditioning system that provides habitable
interior environments.
WHEN: These mitigation measures shall be converted into conditions of approval for the SDP
prior to its final approval by the City's Planning Commission. The building plans will
reflect the noise attenuation measures identified above prior to conditions will become
valid when the SDP is approved and prior to Building Permit issuance. All mitigation
measures must be installed prior to Building Permit final.
WHO: The property owner (developer) will be solely responsible for implementation and
maintenance of these mitigation measures.
HOW: The conditions of approval will require these mitigation measures to be incorporated into
the construction plans.
14. Noise (Less than Significant with Mitigation) - Construction Impacts: The first phase of
construction of the project would occur over an approximate two and one-half year period, followed by
the future construction of the remaining four lots in the second phase. Grading intensive activities would
last 10 to 14 weeks. Noise generating activities would include grading, the establishment of utilities,
construction of streets, construction of 51 new homes, and landscaping. Pile driving or other ground born
vibrations are not an anticipated during construction.
Noise impacts resulting from construction depend on the noise generated by various pieces of
construction equipment, the timing and duration of noise generating activities, and the distance between
construction noise sources and noise sensitive receptors. Construction noise impacts primarily result