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Sonoma County is a drinking destination. Roads swell with traffic on summer weekends when out-of-county visitors go tasting at more than 425 wineries and two dozen breweries that call the county home.
People line up for hours in downtown Santa Rosa every February to get their three 10-ounce glasses of Pliny the Younger triple IPA — a ration designed to prevent people from drinking too much of the high-octane 10.25 percent alcohol beer.
More than 7 million people come to Sonoma County annually, 4.6 million of whom cite beer and wine as their reason for visiting, according to the Sonoma County Economic Development Board.
While some locals blame beer-drinking and wine-tasting tourists for making Sonoma County roadways less safe, the fact is most drunken drivers in Sonoma County are residents whose last drink came at home, a bar or a restaurant.
A Press Democrat analysis of DUI arrest data from the California Highway Patrol Santa Rosa-area office shows people were five times more likely to be arrested on drunken-driving charges coming from a home than from a winery or brewery.
Every week, on average, more than 50 people are arrested on suspicion of driving under the influence of alcohol or drugs somewhere in Sonoma County, The Press Democrat found. The CHP, which makes nearly 40 percent of those arrests, collects data revealing where many were drinking before they got behind the wheel.
More than 35 percent told CHP officers they had been drinking at a bar or restaurant before they were pulled over, while more than 34 percent said they had been drinking at a home, The Press Democrat analysis found. Just under 7 percent told officers they were drinking at a winery or brewery.
The data come from CHP reports detailing where people say they had their last drink prior to a DUI arrest. While people aren’t legally required to tell officers where they were drinking, they do more than half the time, and those are tabulated in so-called “last drink reports.”
Of the 3,155 total DUI arrests made by the CHP in Sonoma County from 2015 to 2017, more than half — 1,672 — told officers where they had their last drink. Those arrests comprise more than one-fifth of the 8,074 total DUI arrests made by law enforcement agencies in Sonoma County over the three years.
The CHP data reveal some regional differences in DUI activity:
— Patrons leaving wineries and breweries account for a much higher proportion of DUI arrests in Healdsburg than other parts of Sonoma County. About 31 percent of respondents who were arrested coming from the Healdsburg area, or 39 people during the three-year period, said they had their last drink at a winery or brewery.
— The Graton Resort & Casino is named more frequently in CHP reports than any other single business in Sonoma County. About 38 percent of respondents arrested coming from Rohnert Park, or 72 people during the three-year period, said they had their last sip in the casino just outside the city’s western edge.
— Visitors to state and regional parks account for a higher proportion of DUI arrests in west Sonoma County than other parts of the county. About 17 percent of respondents who were arrested while driving from west county, or 35 total, had their last drink at a state or regional park.
How we reported this story
To prepare this story, The Press Democrat analyzed 1,672 responses to a question asked by CHP officers when arresting drivers on suspicion of DUI: Where did you have your last drink?
Each response was assigned by The Press Democrat into one of eight categories: residence, bar/restaurant, brewery/winery, beach/park, casino, work, car and other.
The data were derived from questions posed during 3,155 CHP arrests in Sonoma County between 2015 and 2017. People arrested are under no obligation to tell officers where they had their last drink; just over half of the people arrested volunteered an answer to the question. The CHP does not verify their responses.
Fewer than 5 percent of the responses were imprecise, leaving room for interpretation. For example, one person who told officers they had their last drink while eating dinner with their mother could have been dining at a restaurant, but in this analysis it’s assumed the dinner was at a home.
The data account for about 21 percent of the 8,074 DUI arrests in the county during the three-year period by 14 law enforcement agencies operating in Sonoma County.
Missing from CHP data are arrests made by its officers in the city of Sonoma and a good chunk of the Sonoma Valley. The CHP office in Napa covers Sonoma County east of Trinity Road at Highway 12 and does not create last-drink reports.
“The state doesn’t require local CHP offices to conduct place-of-last-drink surveys as CHP-Santa Rosa does, so many don’t,” CHP Officer Jon Sloat said.