Agenda - Council - 02/26/2019 - Laserfiche WebLink

Home

Table 24.8: Ground -borne Noise and Vibration Impact Criteria Land Use Category Ground -borne Vibration Impact Levels (VdB re 10-6 in/s) Ground -borne Noise Impact Levels (dB re 20 µ/Pa) Frequent Events' Infrequent Events(2) Frequent Events' Infrequent Events(2) Category 1: Buildings where low ambient vibration is essential for interior operations. 65 VdB(3) 65 VdB(3) -(4) -(4) Category 2: Residences and buildings where people normally sleep. 72 VdB 80 VdB 35 dBA 43 dBA Category 3: Institutional land uses with primary daytime use. 75 VdB 83 VdB 40 dBA 48 dBA (1) "Frequent Events" is defined as more than 70 vibration events per day. Most rapid transit projects fall into this category. (2) "Infrequent Events" is defined as fewer than 70 vibration events per day. This category includes most commuter rail systems. (3) This criterion limit is based on levels that are acceptable for most moderately sensitive equipment such as optical microscopes. Vibration sensitivity manufacturing or research will require detailed evaluation to define the acceptable vibration levels. Enduring lower vibration levels in a building often requires special design of the HVAC systems and stiffened floors. (4) Vibration -sensitive equipment is not sensitive to ground -borne noise. For the RTC project, the potential sources of ground -borne vibration and noise will be the rail corridor along the southern property boundary and traffic noise from Highway 10, County Road 116 and other roads in and around the development. The vibration sensitive land uses for the RTC project can be classified in all three of the above land use categories. Potential Category 1 uses include the proposed hospital/medical center at the site. The FTA Manual cites critical screening distances for Category 1 of 600 feet, Category 2 of 200 feet and Category 3 of 120 feet. As a result, the designers of the project will need to consider these distances in the location of project buildings. In addition, there are several mitigation measures that can be incorporated into the project to reduce impacts from vibration. These include, but are not limited to: Construction Vibration Mitigation 1) Design Considerations and Project Layout: • Route heavily loaded trucks away from residential streets, if possible. Select streets with fewest homes, if no alternatives are available. • Operate earthmoving equipment as far away from existing occupancies as possible. 2) Sequence of Operations: • Phase demolition, earthmoving and ground -impacting operations so as not to occur in the same time period. Unlike noise, the total vibration level produced could be significantly less when each vibration source operates separately. 23/24-9