So are you more 680/24? YVB stretches quite a bit to the east so you could be Lafayette, Walnut Creek, Alamo, Danville?
That's kind of a dead spot for scanning in general I've noticed when I used to commute up and down 680. Once I hit Main Street or Treat Blvd things opened up a bit. They are supposed to be installing a new tower, if everything goes as planned, at the current BART tower. That's at the NW corner of the 680/24 interchange just north of the BART tracks. That should improve things, but it might be a little while.
Other than that, I'd say try a better antenna or something directional. Everyone has a problem with these simulcast systems, especially on Unidens, but it's better on the GRE's.