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Impact Report for the Bemal Property, dated May 1997, provided noise measurement results at twelve locations within the 318-acm site. Noise levels were measured at three sites within the Central Area: Bernal Avenue (#6 - 70 Ldn (dB)); UPRR (#4 - 62 Ldn (dB)); 1-680 Freeway (#3 - 73 Ldn (dB)). Noise levels related to the freeway were determined to be the most impacting. In addition, it was discovered that noise levels in the southern portions of 1-680 are lower than expected nearer the freeway and higher than expected farther from the freeway, due to the freeway being elevated above the UPRR. Freeway noise has the greatest impact on the site. According to the Final Environmental Impact Report (FEIR) for the Bernal Property, the mitigated 65-decibel sound level is measured at about 400 feet from the eastern edge of the 1-680 Freeway, beginning at the southern edge of the proposed office park and then expanding to 1,000 feet at Laguna Creek Lane. See Attachment 'A' for a diagram of the Bernal Avenue and Valley Avenue sites, overlaid with noise contours near the freeway. Noise levels from Bernai Avenue are estimated to be below 60 decibels (dB) at a distance of 400 feet from Bernal Avenue and at 65 decibels at 100 feet west of the UPRR. The noise generated by the railroad, however, is less significant than ground vibration, which can be mitigated with underground noise dampers on the CAC site, should future studies deem it necessary. Sound Generated at the Amphitheatre Sound in amphitheatres is "bi-directional" - it broadcasts directly out to the audience and it also broadcasts directly back at the performers, who rely on monitor speakers to hear what they're playing. As a result, the orientation of the amphitheater, in relation to off-site uses, creates the sound path out from the stage and back into the stage. The 'bleed' of sound, often at high decibel readings, into local residential areas is a common problem. This can occur as direct sound passing through buildings or barriers, or as ambient sound echoing up and out into the atmosphere. Amphitheatres that use architecture to enclose and buffer event sound can reduce noise levels in adjacent neighborhoods. Back-to-back orientation of stage houses, as well as an enclosed stage shed for the amphitheatre may be proposed to reduce nearly all objectionable sound reflecting off-site. Sound projecting from speakers out to the audience, along the axis of the amphitheatre must be oriented so as to minimize its affect on neighboring residents. The height of the stage shed shou!d be approximately 50' - 60', so as to allow speakers to be oriented downward toward the audience. The stage and bowl should be oriented away from adjacent residential areas. Noise Implications at the Bemal Avenue (north) Location Off-site noise impacts include traffic sounds from Bemal Avenue as well as sounds from Interstate 1-680. Site visits at commute times have confirmed that noise from Bemal traffic is significant within 100 feet of the right- of-way. The proposed 600-foot distance to the CAC buildings and arranging the gallery (Building B), sub- page 2 I M.D. FOTHERINGHAM, LandscapeArchimculnc. 323GearyS=eeg Suit407 San Franchco, CA 94102 415-434-8292