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(Leq) at 200 feet from the source. Receptors that were used to determine noise impact were two existing residences closest to the quarry area, and two locations on the residential-zoned area on the bluff to the southwest, also close to the quarry area (see Figure 3.6-2). Maximum, worst-case noise levels at these four receptors were calculated by taking the combined noise levels at a point within the quarry area closest to each residence and using the standard distance attenuation equation to assess noise levels from the proposed project. The average project-related, worst-case noise levels (resulting noise levels from quarry activities at point closest to residences) (CNEL) were then compared and added (logarithmically) to existing noise levels at the receptors. The existing noise levels were estimated from the highway noise contours. The results of this assessment are shown in Table 3.6-5. The average noise levels at these receptors form quarry activities during the first five years (rather than the temporary, worst-case noise levels as described above) in the Phase I area were calculated by taking a point approximately in the center (see Figure 3.6-2) of the Phase I extraction site (rather than the closest point), and using the distance attenuation equation to assess resulting noise levels at the receptors. These results are also shown in Table 3.6-5. The resulting noise levels were determined using an attenuation rate of 6 dBA per doubling of distance, which is the standard rate to use for a point source to account for atmospheric absorption. This attenuation rate does not account for natural or man- made barriers, such as structures, trees, shrubs, or the effect of the bluff blocking the line of sight between the receptor and the noise source; therefore, the noise levels in Table 3.6-5 would probably be higher than the actual noise levels. The decrease in the noise levels shown in Table 3.6-5 from these barriers would be from 3 dBA to 24 dBA; 3 dBA if there was only minimal vegetation screening, and 24 dBA if the bluff edge acts like a complete barrier of the line-of-sight (Afestre and Woolen, 1980). A comparison of these noise levels, which were extrapolated from using empirical noise data, to noise levels measured at landfill site (Diose), and Russo, 1989) also reveals that the noise levels in Table 3.6-5 may represent a high estimate. Noise at the landfill consisted of compactor operations, bulldozer operations, truck traffic to and from the dump site, waste dropping and crushing, and back-up warning alarms on the bulldozer. These are similar noise sources as would be at the quarry site. The average sound level 88