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Acoustics experts say predicted noise for Project Tango falls within ambient levels; commissioners press for demonstrations
Summary
Consultants presented ambient monitoring and predictive modeling that showed DBA values similar to existing noise and predicted DBC (low‑frequency) levels comparable to background; experts said results meet county standards but commissioners asked for further demonstrations and clarity.
Mark Bastash, an acoustical specialist, told the board that ambient sound near the site generally fluctuates around 50 dBA and that the project's modeled contours show levels of about 45 dBA at the western edge of Arden and the nearby school. He said the three‑dimensional model used ISO 9613‑2 methodology with conservative (downwind) assumptions.
Low‑frequency expert Dr. Norm Bridal said he applied c‑weighted criteria and additional analyses and concluded the predicted C‑weighted (dBC) levels would be similar to current ambient and not at levels commonly associated with adverse health effects. Dr. Chris Olsen (environmental health) said disposal and health risk thresholds were well above predicted project levels. Commissioners repeatedly asked for practical demonstrations; as a short test while the room quieted, Bastash recorded approximately 43.9 dBA and 59.8 dBC to give the board an audible reference point.
