Triad/PUC will account for 100% of the growth in unicorporated Napa County for the next 20 years.
According to the article in the St Helena Star "Bay Area growing by 2 million"
Napa has 134,000 people in 2005 and that is expected to rise to 156,000 in 2035.
90% of the growth is expected to take place in Napa City and American Canyon.
That leaves 10% for unincorporated Napa County.
So, 156000 - 134000 = 22000 * 10% = 2200 people in unicorporated Napa County over the next 30 years.
Average people per house in Angwin is 2.68 * 591 = 1584 / 2200 = 72% or 100% for the next 22 years.
Average household size is from US Census 2000 for Angwin, 591 from Triad.
The Star also ran a story describing how affordable housing requirements are being reduced. They also point out how the focus on housing is where the jobs are. Where are the jobs in Angwin?