In Brydon v. East Bay Mun. Utility Dist. (1994), water customers challenged a new rate structure as a special tax. the inclined rate structure increased price per cubic foot for increased usage. The Court of Appeal found San Diego Gas & Electric Co. "a sustainable analogy."Just as the regulatory scheme set forth by the [air pollution control district] was designed to achieve a legislatively mandated ecological objective, so is the inclined block rate structure of the District a response to state-mandated water-resource conservation requirements." (Brydon v. East Bay Mun. Utility Dist., supra, 24 Cal. App. 4th at p. 192.) The court emphasized the latitude necessary to set the amount of fees to meet the regulatory objectives. "In pursuing a constitutionally and statutorily mandated conservation program, cost allocations for services provided are to be judged by a standard of reasonableness with some flexibility permitted to account for system-wide complexity. . . In short, California Constitution, article XIII a does not apply to every regulatory fee simply because, as applied to one or another of the payor class, the fee is disproportionate to the service rendered." (Id. at pp. 193-194.)