One source of the controversy surrounding Fairfax's just-repealed ordinance that would have facilitated construction of 124 new housing units in the Ross Valley community, is that when it comes to Bay Area planning, 124 doesn't mean 124.

Thanks to California laws mandating housing "density bonuses," when certain criteria are met, 124 can really mean something significantly higher than the number of residential units contained in any particular zoning ordinance's text.

The confusion associated with housing density bonuses inevitably fuels public distrust of government. The state Legislature and its regional minions, including the Association of Bay Area Governments, invented and then adopted upzoning bonuses that automatically increase density, effectively overriding local planning.

Once zoning is established or project approval is granted, there is a "bonus" of an extra 25 percent of units for developers who designate at least 20 percent of the projected units for lower-income residents. An additional 10 percent is granted for very-low-income apartments and 50 percent more for senior-allocated housing.

Incentives are fine, but the number of units assigned after bonuses are calculated are the numbers that need to be disclosed in black letters when zoning is set or specific plans considered. 
In their booklet "Density Through Affordability," the prominent law firm of Kronick, Moskovitz, Tiedemann and Girard advises potential clients, "This ability to force the locality to modify its normal development standards is sometimes the most compelling reason for the developer to structure a project to qualify for the density bonus."
Real estate lawyers understand that developer profitability is all about density and that state-mandated bonuses equal increased density. They know going in what they can get. It's time the public is supplied the same information in an easy-to-understand fashion well before zoning regulations or housing developments are approved.

Editors Note:  It is even worse than this.  The Community development department counts under counts smaller units and studios as "less than a full unit.  Therefore the development that has 82 units like Marinwood Village may actually build up to 164 studio apartments PLUS a density bonus of 32 units for a total of 196 units!   Funny thing, these people have cars, need government services just like the rest of us but the non profit developer can AVOID the majority of taxes for 55 years!