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The unattenuated 70 CNEL contour will fall between 66 and 130 feet from the <br />centerline of Bristol Street in the design year without the proposed <br />improvements. With the proposed project, the unattenuated 70 CNEL contour <br />will fall between 70 and 132 feet from the centerline. The unattenuated 65 <br />CNEL contour will fall between 192 and 404 feet from the centerline, <br />depending upon the link and scenario under consideration. <br />Federal Standards: Table 17 details the future design year maximum hourly <br />equivalent noise levels adjacent to each roadway link with and without the <br />proposed widening. Under federal noise standards, traffic impacts occur when <br />predicted noise levels approach or exceed the noise abatement criteria, or <br />when predicted levels substantially exceed the existing noise levels. <br />With the no -build alternative, the unattenuated 67 dBA contours will be <br />located between 114 feet and 235 feet from the centerline. The unattenuated <br />62 dBA contours will be located between 351 feet and 739 feet from the <br />Bristol Street centerline. <br />With the build alternative, the unattenuated 67 dBA contours will be located <br />between 116 and 236 feet from the centerline. The unattenuated 62 dBA <br />contours will be between 352 and 739 feet from the centerline. <br />Although only exterior noise criteria are applicable to this project, the 62 dBA <br />contour locations are provided within Table 17 so that interior noise levels can <br />be determined for comparison to the FHWA design criteria. Since FHWA <br />allows a 10 dBA noise reduction factor for buildings with windows open, the <br />location of the 62 Leq contour provides the point where interior noise levels <br />of.52 dBA would occur when windows are open. <br />Sensitive Receptor Analysis <br />The 15 noise measurement locations (on 13 lots) were analyzed for future <br />noise impacts with three project alternatives and the no- project alternative. - <br />These locations are shown in Figures 13A - 13B (pages III -18 and 111-19) and <br />Figures 19A - 19F (pages IV -33 through IV -38). For each of the project <br />alternatives, exterior noise levels were calculated for the no mitigation <br />condition and with 6 -foot and 8 -foot barriers. In addition, the barrier height <br />for a 5 dB attenuation over the no mitigation condition (minimum 6 -foot wall), <br />and the barrier height required to break line -of -sight to a 11.5 -foot high diesel " <br />exhaust stack were determined. <br />IV -24 <br />75C -159 <br />