Cal. Pub. Resources Code § 41760
The countywide integrated waste management plan and any amendments thereto, with the exception of any source reduction and recycling element, household hazardous waste element, or nondisposal facility element, prepared by a city or county, shall be approved by the county and by a majority of the cities within the county which contain a majority of the population of the incorporated areas of the county, except in those counties which have only two cities, in which case the plan is subject to the approval of the city which contains a majority of the population of the incorporated areas of the county. Each city shall act upon the plan and any proposed amendment within 90 days after receipt of the amendment. If a city fails to act upon the plan or the proposed amendment within 90 days after receiving the plan or the amendment, the city shall be deemed to have approved the plan or the amendment as submitted.
Ca. Pub. Res. Code § 41760