California Code, Streets and Highways Code - SHC § 36731

(a) The assessments levied on real property pursuant to this part shall be levied on the basis of the estimated benefit to the real property within the district.  The city council may classify properties for purposes of determining the benefit to property of the improvements and activities provided pursuant to this part.

(b) Assessments levied on businesses pursuant to this part shall be levied on the basis of the estimated benefit to the businesses within the district.  The city council may classify businesses for purposes of determining the benefit to the businesses of the improvements and activities provided pursuant to this part.

(c) Properties used for single-family residential use, or that are zoned for agricultural use, are conclusively presumed not to benefit from the improvements and service funded through these assessments, and shall not be subject to any assessment pursuant to this part.