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How is the Marin/Sonoma Mosquito & Vector Control District funded?

The Marin/Sonoma Mosquito & Vector Control District is a California Independent Special District and is principally funded by a very small portion (equivalent to its share prior to 1978) of the ad valorem property taxes collected by the County Tax Collectors. The second-largest source of financial support comes from two benefit assessments, which are annual service charges assessed on all non-exempt land parcels in the service area. Each year an Engineer’s Report (available for download on this site) details the special benefits accruing to each land parcel and the Board of Trustees sets the amount of the benefit assessment following a public hearing, typically in late Spring.

Due to a cap imposed when the main benefit assessment covering the majority of the two counties was set up in 1996, the annual amount for a single family equivalent parcel is $12 and can never be increased. Areas of West Marin and Sonoma Counties that voted to annex to the District in 1994 pay approximately $23 per parcel, but do not contribute ad valorem revenue, so the amount paid per households in both assessment districts is very similar.

Although the District does not charge fees to home and business owners for its services, and most public entities are exempt from the paying the benefit assessments described above, the District bills approximately $200,000 per year to agencies to which it provides contract services e.g. California Department of Fish and Wildlife and certain Sanitary Districts. The smallest source of revenue is the interest that the District earns interest on reserve funds kept on deposit for purposes such as emergencies and replacement of capital items.


The laws governing Benefit Assessments do not provide for any exemptions such as the senior, disability, low income or veterans property tax exemptions. Benefit Assessments are fundamentally different from property taxes as they reflect the provision of a direct benefit to the property and its residents, as opposed to a general tax assessed according to the property’s value (ad valorem tax).

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