Updated 4 p.m.: The mystery of the aroma appears to have been solved: Please see .
The Facebook posts started around noon Thursday on the Napa Patch page:
Chris Shepard-Brown: "Why does So. Napa, River Park area smell like S_ _ _ _ today? Is it Napa sanatation or the recycle plant? Any ideas?"
Casey Thirnbeck-Scott: "I'm curious too! I smelled it yesterday!"
Cathy White Martin: "Does anyone know what is making Napa smell like "Dog-Doodoo"?"
Cesar Brambila: "whats with the nasty smell ??"
Napa Patch is a lot like a radio station sometimes: We take requests, so I called the and talked with Seth Anderson about the mystery smell.
"Nobody's been able to get a handle on it," he said.
City workers called , and the dump and "none of them are doing anything out of the ordinary," Anderson continued.
"The consensus is that it's harvest" and that the aroma is winery-related, Anderson said.
Residents concerned about the odor can contact the , www.baaqmd.gov to request an investigation, he said.
The harvest theory was immediately challenged in comments on Twitter, Facebook and on this page. A sample of the social media responses:
Matthew Young: "I know what fermenting grapes smell like. This smell liked feces. I've encountered a similar scent in downtown San Francisco and it's far more unpleasant than the smell of grapes."
Kim Schulz-Ponciano: "Sorry that is not fermentation, it was gagging me all the way on terrace and coombsville. Smelled like cat boo boo."
And then came a Facebook post from Jennifer Schindler Keiser: "They are working in the marsh out on Highway 37. Digging up old, nasty marsh soil. It smells all the way in Fairfield!"
What do you think it is? Do you smell it? Where in Napa are you located? Let's see how widespread the aroma is, and how long it lasts: Share your observations in the comments. If you'd rather remain anonymous, you're welcome to email your comment to me at email@example.com.