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Air Quality

The Petaluma Gap

Geographically, the Petaluma Gap borders West Marin and Valley Ford on the west, then follows Chileno Valley and Spring Hill Roads to Adobe Road on the east, Cotati on the north and Lakeville on the southeast. This is not your normal geography. As inland valley air heats up, it pulls the cool coastal air into a naturally formed 15-mile-wide "gap" in the coastal range mountains. The wind flows off the ocean between Tomales Bay and Bodega Bay, builds up speed as it funnels through the gap, then empties into San Francisco Bay. Wind and fog define the area, giving the term "micro-climate" real meaning.

The daily weather pattern goes something like this: Early-to-mid-morning finds a distinctive crisp coolness and a blanket of fog. By late morning the sun has chased away the fog and the temperature rises. By mid-afternoon, however, the cool breezes return, flowing west to east, picking up speed as the afternoon progresses and bringing in the almost nightly fog. There are daily temperature swings of forty to fifty degrees. This cooling "wind tunnel" effect means the vineyard yields are smaller and grapes ripen later, developing wonderful flavors and fruit characteristics, while maintaining ideal levels of acidity. It's the perfect recipe for intense but well-balanced wines."

Source: Petaluma Gap Winery Alliance.

Every Which Way the Wind Blows

At the Planning Commission on April 1, 2010 Blake Hillegas, County Planning staff,  said the Final Environmental Impact Report (FEIR) wind measurements of 25 mph came from Valley Ford, 60 feet above sea level, the closest wind monitoring available.  The gravel mine site elevation is 550 feet above sea level and will have higher wind speeds. The proposed gravel mine is situated in the Petaluma Wind Gap, with wind rushing through the Roblar valley at high speeds 9 months of the year.   Among the public's many concerns for health and safety,  wind will negatively affect water use for dust control at the quarry site, two very important issues for this project.

Wind speeds in the Roblar area have never been tested at the quarry site.  Instead, the County has used data gathered from the Valley Ford meteorlogic station eight miles to the west of the quarry and the airport in Santa Rosa.  The Bay Area Air Quality Management District (BAAQMD) commented that the project's FEIR used wind data from the Valley Ford meteorologic station, and that the project lies outside the area represented by this station.  Yet BAAQMD did not require wind monitoring data from the project site.  How can they  accurately determine health risks and dust control without knowing  the wind speeds at the site? How much silica is going to blow into resident homes, Dunham School and  eastward into Cotati?  CARRQ has repeatedly asked the County to measure wind speeds at the quarry site.

Blasting Particulates

The  Environmental Impact Report (EIR) states that projected nitrous oxide emissions from the project will be 53.3 tons more than the allowable threshold in the first year the quarry would operate. Even with all mitigations in place the emissions would be  21.6  tons over the allowable threshold.   This is considered significant and unavoidable in the EIR. Most of these emissions will be blowing through the Roblar  Road Valley.  This is a concern for the respiratory health of residents in this valley.

Silica dust is a known carcinogen.

Blake Hillegas of the County Planning staff stated at the Planning Commission on April 1, 2010 about the lack of asbestos and the presence of silica in the proposed Roblar quarry:  "The DEIR dispersion modeling conservatively assumed 100% silica content, which poses no significant adverse health risks according to applicable standards in a separation from residential uses."

There is nothing in this statement to address the silica content in the dust that will most certainly blow through the Roblar neighborhood, as the wind is from the southwest.  There is no explanation of his comment about "residential uses" which perhaps refers to use of the rock in building housing.