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5.0 Environmental Analysis 5.6 Noise Avion Project SEIR Page 5.6-8 Additionally, empirical data has shown that delays of as little as 5 milliseconds can minimize vibration in very close blasting situations (10 to 25 feet) (Bender 2007). Table 5.6-2 Predicted Blasting Vibration Levels by Charge Weight Distance to Non-Rippable Rock (feet) Predicted Vibration Level by Charge Weight (in/sec PPV) 12 lb. 10 lb. 8 lb. 4 lb. 2 lb. 1 lb. 0.5 lb. 0.25 lb. 10 130.93 113.16 94.66 54.37 31.23 17.93 10.30 5.92 50 9.97 8.62 7.21 4.14 2.38 1.37 0.78 0.45 100 3.29 2.84 2.38 1.37 0.78 0.45 0.26 0.15 150 1.72 1.49 1.24 0.71 0.41 0.24 0.14 0.08 175 – nearest residence 1.34 1.16 0.97 0.56 0.32 0.18 0.11 0.06 200 1.08 0.94 0.78 0.45 0.26 0.15 0.09 0.05 in/sec = inches per second; PPV = peak particle velocity; lb. = pounds NOTE: Bold numbers indicate an exceedance of 2.0 in/sec PPV, which would be considered an impact. As shown in Table 5.6-2, the nearest receiver located 175 feet to the northeast of the proposed blasting locations is not anticipated to be exposed to vibration levels in excess of 2.0 in/sec PPV. Although a project-specific blasting plan and exact amount of explosive needed is not known at this time, the project would comply with the County Fire Code and would implement all feasible vibration reduction strategies, including conducting pre- and post-construction surveys of the nearest residence to any blast. The project would also monitor blasting vibrations and overpressure levels, the results of the monitoring would be used to reduce charge weights, increase timing between charges, or other appropriate measures as required to reduce vibrations from blasting. Furthermore, the proposed blasting activities would be subject to the following County Fire Code (County of San Diego 2017) and City requirements: 1. Per Section 59.5.0404 of the City’s Noise Abatement and Control Ordinance, construction, including blasting, shall be prohibited between the hours of 7:00 p.m. and 7:00 a.m., or on Sundays, or on legal holidays as specified in Section 21.04 of the San Diego Municipal Code, with exception of Columbus Day and Washington’s Birthday. 2. The blasting contractor shall obtain a permit from the Fire Chief of the City of San Diego per the requirements of Section 53.01 of the Municipal Code. 3. Blasting activities would follow guidance provided in the General Blasting Management Plan that would include an estimate of air blast overpressure and vibration levels of each shot at the nearest structure. A preliminary General Blasting Management Plan is included as Attachment 1. Blasting shall not commence until the City and Sherriff’s Department has approved the General Blasting Management Plan. 4. Each blast shall be monitored and recorded with an air blast over-pressure monitor that is located outside the nearest residence to the blast. 5. The City project engineer shall review the request for each blast to verify blasting only of material that requires blasting.