Page 637 - northlakehills_deir_0517
P. 637
NorthLake Specific Plan
Draft Supplemental EIR
The listing of vibration levels and air overpressure levels in Table 5.10-13 above does not indicate
that there is any connection between the two, except as the particular levels apply to human
response. In blasting, an increase in vibration can often be accompanied by a decrease in air
overpressures, and vice versa.
In reviewing the above responses, one must distinguish between the average individual and those
who may reside at either end of the human response spectrum. At one end are persons who
might perceive some financial benefit or common good from the Project. Although they may not
appreciate the inconvenience of the blasting, unless they are physically damaged in some
manner, they may not complain. At the other end of the spectrum, individuals who do not want
the Project to take place may be disturbed by the slightest inconvenience and will generally make
their feelings known (Caltrans 2013b).
Blasting Impacts
As described above, there are many factors affecting blast impacts including but not limited to:
distance between the blast location and the receptors, charge weight, depth of burial of the
charge, geologic formations, and atmospheric conditions. However, the quantity of blasting
required and the various parameters, such as frequency, charge weight, are not known and
cannot be quantified until site conditions, including geological and atmospheric data, and Project
requirements are reviewed by a blasting expert when blasting is required. Therefore, there would
be a potentially significant noise and vibration impact and mitigation is required (refer to
MM 5.10-12).
Level of Significance without Mitigation: Construction: Potentially significant.
Recommended SCVAP EIR Mitigation Measures: None
Level of Significance with SCVAP EIR Mitigation Measures: Potentially significant.
Recommended 1992 EIR Mitigation Measures: The 1992 SP EIR did not include a noise
analysis; therefore, no mitigation measures or impacts relevant to noise are carried forward.
Level of Significance with 1992 EIR Mitigation Measures: Potentially significant.
Recommended Project-Specific Mitigation Measures:
MM 5.10-12 If blasting is required, the Applicant or its contractor shall hire a certified blasting
expert to develop a blasting program to be approved by the County Department of
Public Works. The program shall include but not be limited to the following
elements:
• Design the blast to limit noise and vibration at any residence or the
NorthLake Elementary School to the limits recommended by the Office of
Surface Mining Reclamation and Enforcement or similarly recognized
authority.
• Based on the blasting locations, define an impact area where noise and
vibration impacts are anticipated to be distinctly perceptible.
• Inform all homeowners and tenants in the impact area of the Project, the
planned blasting program, and the anticipated noise and vibration impacts.
In addition to printed literature, have a public meeting. Provide a contact
for homeowners for pre- and post-blast questions.
R:\Projects\OC\WCP_Woodrid\J0001\Draft EIR\5.10 Noise-042617.docx 5.10-33 Noise
